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Journal articles on the topic 'Weak topological insulators'

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Author: Grafiati

Published: 6 September 2023

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1

Li, Bo-Wen, Xiao-Chen Sun, Cheng He, and Yan-Feng Chen. "Acoustic graphyne: A second-order real Chern topological insulator." Journal of Applied Physics 133, no. 8 (February 28, 2023): 085107. http://dx.doi.org/10.1063/5.0132983.

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Graphyne has recently attracted much attention since it is an important derivative of graphene with unique topological properties. Although graphyne is not a conventional topological insulator because of its weak spin–orbit coupling, it is a real Chern topological insulator with the higher-order topology. However, it lacks a realistic model. Here, we propose a schedule to realize acoustic graphyne. By introducing negative coupling to simulate the carbon–carbon triple bond, we realize the transition from trivial to higher-order topological phases, characterized by real Chern numbers. These topologically protected corner states are achieved in a finite-size sample, and the condition for their existence is discussed. Our research extends the concept of real Chern insulators and provides a platform for studying the topological properties of graphene-like structural compounds.

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2

Zhu, Qing-Li, Liang Hua, and Ji-Mei Shen. "Theoretical construction of weak topological crystalline insulators." International Journal of Modern Physics B 31, no. 20 (August 10, 2017): 1750136. http://dx.doi.org/10.1142/s0217979217501363.

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Inspired by the discovery of topological crystalline insulators (TCIs) in three-dimensional materials such as Pb[Formula: see text]Sn[Formula: see text]Se(Te), the classification of topological insulators has been extended to other discrete symmetry classes such as crystal point group symmetries. In this paper, we construct and study a simple model of weak TCIs, which will serve as a more viable project in the experimental probe for such new type of topological phases.

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3

Lang, Murong, Liang He, Xufeng Kou, Pramey Upadhyaya, Yabin Fan, Hao Chu, Ying Jiang, et al. "Competing Weak Localization and Weak Antilocalization in Ultrathin Topological Insulators." Nano Letters 13, no. 1 (December 7, 2012): 48–53. http://dx.doi.org/10.1021/nl303424n.

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4

Yang, Huanhuan, Lingling Song, Yunshan Cao, and Peng Yan. "Experimental Realization of Two-Dimensional Weak Topological Insulators." Nano Letters 22, no. 7 (March 30, 2022): 3125–32. http://dx.doi.org/10.1021/acs.nanolett.2c00555.

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5

Chang, Kai-Wei, Wei Ji, and Chao-Cheng Kaun. "Layer-separable and gap-tunable topological insulators." Physical Chemistry Chemical Physics 19, no. 5 (2017): 3932–36. http://dx.doi.org/10.1039/c6cp06932k.

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6

Jun, Jin-Hyeon, Jinsu Kim, Sang Hyun Ji, Sang-Eon Lee, Soo-Whan Kim, Sung Jung Joo, Kyoung-Min Kim, Ki-Seok Kim, and Myung-Hwa Jung. "Negative magnetoresistance in antiferromagnetic topological insulating phase of Gd_xBi_2−xTe_3−ySe_y." APL Materials 11, no. 2 (February 1, 2023): 021106. http://dx.doi.org/10.1063/5.0135811.

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Antiferromagnetic topological insulators have attracted great attention in the condensed matter physics owing to the fundamental interest in exotic quantum states and topological antiferromagnetic spintronics. Starting with the typical topological insulator of Bi2Te3, we introduced the magnetic order by substituting Gd at the Bi site and tuned the Fermi level by substituting Se at the Te site. That is, we prepared single crystals of Gd xBi2− xTe3− ySe y with various x (= 0.02 and 0.06) and y (= 0.1, 0.2, 0.5, 0.7, 1.0, and 1.5). The magnetic data revealed an antiferromagnetic order for x = 0.06, and the transport data manifested the charge neutral point at y = 0.7. Combining all these results together, the material with x = 0.06 and y = 0.7 is characterized as an antiferromagnetic topological insulator, where we observed exotic magnetotransport properties such as weak antilocalization and negative longitudinal magnetoresistance that are frequently analyzed as chiral anomalies in Weyl materials.

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7

Gracia-Abad, Rubén, Soraya Sangiao, Chiara Bigi, Sandeep Kumar Chaluvadi, Pasquale Orgiani, and José María De Teresa. "Omnipresence of Weak Antilocalization (WAL) in Bi2Se3 Thin Films: A Review on Its Origin." Nanomaterials 11, no. 5 (April 22, 2021): 1077. http://dx.doi.org/10.3390/nano11051077.

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Topological insulators are materials with time-reversal symmetric states of matter in which an insulating bulk is surrounded by protected Dirac-like edge or surface states. Among topological insulators, Bi2Se3 has attracted special attention due to its simple surface band structure and its relatively large band gap that should enhance the contribution of its surface to transport, which is usually masked by the appearance of defects. In order to avoid this difficulty, several features characteristic of topological insulators in the quantum regime, such as the weak-antilocalization effect, can be explored through magnetotransport experiments carried out on thin films of this material. Here, we review the existing literature on the magnetotransport properties of Bi2Se3 thin films, paying thorough attention to the weak-antilocalization effect, which is omnipresent no matter the film quality. We carefully follow the different situations found in reported experiments, from the most ideal situations, with a strong surface contribution, towards more realistic cases where the bulk contribution dominates. We have compared the transport data found in literature to shed light on the intrinsic properties of Bi2Se3, finding a clear relationship between the mobility and the phase coherence length of the films that could trigger further experiments on transport in topological systems.

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8

Takane, Yositake. "Landau Levels on a Surface of Weak Topological Insulators." Journal of the Physical Society of Japan 84, no. 8 (August 15, 2015): 084710. http://dx.doi.org/10.7566/jpsj.84.084710.

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9

Seiberg, Nathan, and Edward Witten. "Gapped boundary phases of topological insulators via weak coupling." Progress of Theoretical and Experimental Physics 2016, no. 12 (November 4, 2016): 12C101. http://dx.doi.org/10.1093/ptep/ptw083.

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10

Zhang, Min, Qiya Liu, Ligang Liu, and Tixian Zeng. "Proximity-Induced Magnetism in a Topological Insulator/Half-Metallic Ferromagnetic Thin Film Heterostructure." Coatings 12, no. 6 (May 31, 2022): 750. http://dx.doi.org/10.3390/coatings12060750.

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Topological insulator (TI) Bi2Se3 thin films were prepared on half-metallic ferromagnetic La0.7Sr0.3MnO3 thin film by magnetron sputtering, forming a TI/FM heterostructure. The conductivity of Bi2Se3was modified by La0.7Sr0.3MnO3 at high- and low-temperature regions via different mechanisms, which could be explained by the short-range interactions and long-range interaction between ferromagnetic insulator and Bi2Se3 due to the proximity effect. Magnetic and transport measurements prove that the ferromagnetic phase and extra magnetic moment are induced in Bi2Se3 films. The weak anti-localized (WAL) effect was suppressed in Bi2Se3 films, accounting for the magnetism of La0.7Sr0.3MnO3 layers. This work clarifies the special behavior in Bi2Se3/La0.7Sr0.3MnO3 heterojunctions, which provides an effective way to study the magnetic proximity effect of the ferromagnetic phase in topological insulators.

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11

Lu, Bing-Sui. "The Casimir Effect in Topological Matter." Universe 7, no. 7 (July 9, 2021): 237. http://dx.doi.org/10.3390/universe7070237.

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We give an overview of the work done during the past ten years on the Casimir interaction in electronic topological materials, our focus being solids, which possess surface or bulk electronic band structures with nontrivial topologies, which can be evinced through optical properties that are characterizable in terms of nonzero topological invariants. The examples we review are three-dimensional magnetic topological insulators, two-dimensional Chern insulators, graphene monolayers exhibiting the relativistic quantum Hall effect, and time reversal symmetry-broken Weyl semimetals, which are fascinating systems in the context of Casimir physics. Firstly, this is for the reason that they possess electromagnetic properties characterizable by axial vectors (because of time reversal symmetry breaking), and, depending on the mutual orientation of a pair of such axial vectors, two systems can experience a repulsive Casimir–Lifshitz force, even though they may be dielectrically identical. Secondly, the repulsion thus generated is potentially robust against weak disorder, as such repulsion is associated with the Hall conductivity that is topologically protected in the zero-frequency limit. Finally, the far-field low-temperature behavior of the Casimir force of such systems can provide signatures of topological quantization.

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12

Pan, Lei, Xiaoyang Liu, Qing Lin He, Alexander Stern, Gen Yin, Xiaoyu Che, Qiming Shao, et al. "Probing the low-temperature limit of the quantum anomalous Hall effect." Science Advances 6, no. 25 (June 2020): eaaz3595. http://dx.doi.org/10.1126/sciadv.aaz3595.

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Quantum anomalous Hall effect has been observed in magnetically doped topological insulators. However, full quantization, up until now, is limited within the sub–1 K temperature regime, although the material’s magnetic ordering temperature can go beyond 100 K. Here, we study the temperature limiting factors of the effect in Cr-doped (BiSb)2Te3 systems using both transport and magneto-optical methods. By deliberate control of the thin-film thickness and doping profile, we revealed that the low occurring temperature of quantum anomalous Hall effect in current material system is a combined result of weak ferromagnetism and trivial band involvement. Our findings may provide important insights into the search for high-temperature quantum anomalous Hall insulator and other topologically related phenomena.

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13

Teng, Peng, Tong Zhou, Yonghuan Wang, Ke Zhao, Xiegang Zhu, and Xinchun Lai. "Electrical transport properties of cerium doped Bi₂Te₃ thin films grown by molecular beam epitaxy." Journal of Semiconductors 42, no. 12 (December 1, 2021): 122902. http://dx.doi.org/10.1088/1674-4926/42/12/122902.

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Abstract Introducing magnetism into topological insulators (TIs) can tune the topological surface states and produce exotic physical effects. Rare earth elements are considered as important dopant candidates, due to their large magnetic moments from heavily shielded 4f electrons. As the first element with just one 4f electron, cerium (Ce) offers an ideal platform for exploring the doping effect of f-electron in TIs. Here in this work, we have grown cerium-doped topological insulator Bi2Te3 thin films on an Al2O3(0001) substrate by molecular beam epitaxy (MBE). Electronic transport measurements revealed the Kondo effect, weak anti-localization (WAL) effect and suppression of surface conducting channels by Ce doping. Our research shows the fundamental doping effects of Ce in Bi2Te3 thin films, and demonstrates that such a system could be a good platform for further research.

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14

Takane, Yositake. "Delocalization of Surface Dirac Electrons in Disordered Weak Topological Insulators." Journal of the Physical Society of Japan 83, no. 10 (October 15, 2014): 103706. http://dx.doi.org/10.7566/jpsj.83.103706.

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15

Sun, X., G. Adamo, M. Eginligil, H. N. S. Krishnamoorthy, N. I. Zheludev, and C. Soci. "Topological insulator metamaterial with giant circular photogalvanic effect." Science Advances 7, no. 14 (April 2021): eabe5748. http://dx.doi.org/10.1126/sciadv.abe5748.

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One of the most notable manifestations of electronic properties of topological insulators is the dependence of the photocurrent direction on the helicity of circularly polarized optical excitation. The helicity-dependent photocurrents, underpinned by spin-momentum locking of surface Dirac electrons, are weak and easily overshadowed by bulk contributions. Here, we show that the chiral response can be enhanced by nanostructuring. The tight confinement of electromagnetic fields in the resonant nanostructure enhances the photoexcitation of spin-polarized surface states of topological insulator Bi1.5Sb0.5Te1.8Se1.2, leading to an 11-fold increase of the circular photogalvanic effect and a previously unobserved photocurrent dichroism (ρcirc = 0.87) at room temperature. The control of spin transport in topological materials by structural design is a previously unrecognized ability of metamaterials that bridges the gap between nanophotonics and spin electronics, providing opportunities for developing polarization-sensitive photodetectors.

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16

Muntyanu, Fiodor M., Konstantin Nenkov, Andrzej J. Zalesk, Elena Condrea, and Vitalie Chistol. "Various manifestations of weak magnetism and superconductivity in inclination interfaces of Bi, Sb and Bi1-xSbx." Moldavian Journal of the Physical Sciences 20, no. 2 (January 2022): 129–35. http://dx.doi.org/10.53081/mjps.2021.20-2.03.

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The magnetic properties of the nano-width bicrystal interfaces (CIs) of Bi, Sb and 3D topological insulator Bi1xSbx (0.06 ≤ x ≤ 0.2) are studied in a temperature range of 1.6–300 K. These materials do not show superconductivity under normal rhombohedral conditions and are anomalous diamagnetics. At the same time, two superconducting phases with Tc ≤ 21 K and magnetic hysteresis loops against a diamagnetic background typical for strong type II superconductors are identified in Bi interfaces. At the CIs of Bi1xSbx (0.06 ≤ x ≤ 0.2), as well as Sb, a superconducting transition and a ferromagnetic hysteresis loop or a dual loop (superimposed ferromagnetic and superconducting loops) against a paramagnetic background are observed; they indicate the simultaneous occurrence of superconductivity and weak ferromagnetism, which is specific to 3D topological insulators. The revealed coexistence of superconductivity and weak magnetism at these CIs is of significant interest for the fundamental physics and future applications in quantum computing and spintronic devices.

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17

Irfan, Bushra, Bhanu P. Joshi, A. Thamizhavel, Mandar M. Deshmukh, and Ratnamala Chatterjee. "Gate tuned weak antilocalization effect in calcium doped Bi2Se3 topological insulators." Solid State Communications 220 (October 2015): 45–48. http://dx.doi.org/10.1016/j.ssc.2015.07.007.

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18

Kölzer, Jonas, Abdur Rehman Jalil, Daniel Rosenbach, Lisa Arndt, Gregor Mussler, Peter Schüffelgen, Detlev Grützmacher, Hans Lüth, and Thomas Schäpers. "Supercurrent in Bi4Te3 Topological Material-Based Three-Terminal Junctions." Nanomaterials 13, no. 2 (January 10, 2023): 293. http://dx.doi.org/10.3390/nano13020293.

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In this paper, in an in situ prepared three-terminal Josephson junction based on the topological insulator Bi4Te3 and the superconductor Nb the transport properties are studied. The differential resistance maps as a function of two bias currents reveal extended areas of Josephson supercurrent, including coupling effects between adjacent superconducting electrodes. The observed dynamics for the coupling of the junctions is interpreted using a numerical simulation of a similar geometry based on a resistively and capacitively shunted Josephson junction model. The temperature dependency indicates that the device behaves similar to prior experiments with single Josephson junctions comprising topological insulators’ weak links. Irradiating radio frequencies to the junction, we find a spectrum of integer Shapiro steps and an additional fractional step, which is interpreted with a skewed current–phase relationship. In a perpendicular magnetic field, we observe Fraunhofer-like interference patterns in the switching currents.

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19

Paixão, José A., Marta S. C. Henriques, Carlotta Micale, Elsa B. Lopes, Vanda M. Pereira, and António P. Gonçalves. "Quantum effects in electrical transport properties of Bismuth chalcogenides Topological Insulators." EPJ Web of Conferences 233 (2020): 01001. http://dx.doi.org/10.1051/epjconf/202023301001.

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Quantum effects such as weak-antilocalisation (WAL) behavior and Shubnikov-de Haas (SdH) oscillations in the electrical transport properties of topological insulators, measured on nanostructured polycrystalline samples and single-crystals of a series of bismuth chalcogenide compounds (Bi2(SexTe1-x)3, 0 ≤ x ≤ 1 and BiSbTe3), are presented and discussed.

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20

Brahlek, Matthew, Nikesh Koirala, Namrata Bansal, and Seongshik Oh. "Transport properties of topological insulators: Band bending, bulk metal-to-insulator transition, and weak anti-localization." Solid State Communications 215-216 (July 2015): 54–62. http://dx.doi.org/10.1016/j.ssc.2014.10.021.

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21

Ren, Ceng-Ceng, Wei-Xiao Ji, Shu-Feng Zhang, Chang-Wen Zhang, Ping Li, and Pei-Ji Wang. "Strain-Induced Quantum Spin Hall Effect in Two-Dimensional Methyl-Functionalized Silicene SiCH3." Nanomaterials 8, no. 9 (September 7, 2018): 698. http://dx.doi.org/10.3390/nano8090698.

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Quantum Spin Hall (QSH) has potential applications in low energy consuming spintronic devices and has become a researching hotspot recently. It benefits from insulators feature edge states, topologically protected from backscattering by time-reversal symmetry. The properties of methyl functionalized silicene (SiCH3) have been investigated using first-principles calculations, which show QSH effect under reasonable strain. The origin of the topological characteristic of SiCH3, is mainly associated with the s-pxy orbitals band inversion at Γ point, whilst the band gap appears under the effect of spin-orbital coupling (SOC). The QSH phase of SiCH3 is confirmed by the topological invariant Z2 = 1, as well as helical edge states. The SiCH3 supported by hexagonal boron nitride (BN) film makes it possible to observe its non-trivial topological phase experimentally, due to the weak interlayer interaction. The results of this work provide a new potential candidate for two-dimensional honeycomb lattice spintronic devices in spintronics.

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22

Kubota, Yosuke. "The bulk–dislocation correspondence for weak topological insulators on screw–dislocated lattices." Journal of Physics A: Mathematical and Theoretical 54, no. 36 (August 13, 2021): 364001. http://dx.doi.org/10.1088/1751-8121/ac190c.

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23

Trivedi, Tanuj, Sushant Sonde, Hema C. P. Movva, and Sanjay K. Banerjee. "Weak antilocalization and universal conductance fluctuations in bismuth telluro-sulfide topological insulators." Journal of Applied Physics 119, no. 5 (February 7, 2016): 055706. http://dx.doi.org/10.1063/1.4941265.

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24

Komori, Shiryu, and Kenji Kondo. "A proposal of strong and weak phases in second-order topological insulators." Journal of Physics Communications 4, no. 12 (December 17, 2020): 125005. http://dx.doi.org/10.1088/2399-6528/abd0d4.

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25

Liu, Chao-Xing, Xiao-Liang Qi, and Shou-Cheng Zhang. "Half quantum spin Hall effect on the surface of weak topological insulators." Physica E: Low-dimensional Systems and Nanostructures 44, no. 5 (February 2012): 906–11. http://dx.doi.org/10.1016/j.physe.2011.11.005.

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26

Wei, Ping, Jiong Yang, Liang Guo, Shanyu Wang, Lihua Wu, Xianfan Xu, Wenyu Zhao, et al. "Minimum Thermal Conductivity in Weak Topological Insulators with Bismuth-Based Stack Structure." Advanced Functional Materials 26, no. 29 (May 25, 2016): 5360–67. http://dx.doi.org/10.1002/adfm.201600718.

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27

Malasi, Megha, Shivam Rathod, Archana Lakhani, and Devendra Kumar. "Evidence of surface delocalization in ultrathin films of topological insulator in presence of intersurface hybridization and disorder." Applied Physics Letters 121, no. 9 (August 29, 2022): 093101. http://dx.doi.org/10.1063/5.0101268.

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The study of surface transport in ultrathin films of few quintuple layers thick topological insulators (TIs) and its evolution with disorder is important for TI based device engineering. Here, we demonstrate the absence of Anderson localization in surface states of Bi2Se3 films on varying the disorder from the weak to moderate regime. On increasing the disorder, bulk of topological insulator transforms from diffusive to hopping transport while surface remains in quantum diffusive regime. The weak antilocalization (WAL) of surface states suppresses in thinner films, which could occur due to disorder or inter surface hybridization. Our analysis rules out the role of disorder in WAL suppression and shows that films crossover from decoupled surface states to a single coupled surface bulk channel and finally to hybridized surface states on reducing the film thickness. The dephasing mechanism of surface transport strongly depends on the nature of bulk transport. It is dominated by 2D electron–electron scattering for diffusive bulk transport while it is dominated by direct surface bulk charge puddle coupling and surface to hopping transport coupling for bulk in the variable range hopping regime. The surface to hopping transport coupling weakens with intersurface hybridization.

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28

Arita, Takashi, and Yositake Takane. "Effective Model for Massless Dirac Electrons on a Surface of Weak Topological Insulators." Journal of the Physical Society of Japan 83, no. 12 (December 15, 2014): 124716. http://dx.doi.org/10.7566/jpsj.83.124716.

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29

Ginting, Dianta, Chan-Chieh Lin, Gareoung Kim, Jae Hyun Yun, Byung-Kyu Yu, Sung-Jin Kim, Kyunghan Ahn, and Jong-Soo Rhyee. "Enhancement of thermoelectric performance via weak disordering of topological crystalline insulators and band convergence by Se alloying in Pb0.5Sn0.5Te1 − xSex." Journal of Materials Chemistry A 6, no. 14 (2018): 5870–79. http://dx.doi.org/10.1039/c8ta00381e.

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30

Arita, Takashi, and Yositake Takane. "Weak Topological Insulators with Step Edges: Subband Engineering and Its Effect on Electron Transport." Journal of the Physical Society of Japan 85, no. 3 (March 15, 2016): 033706. http://dx.doi.org/10.7566/jpsj.85.033706.

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31

Brito, Daniel, Ana Pérez-Rodriguez, Ishwor Khatri, Carlos José Tavares, Mario Amado, Eduardo Castro, Enrique Diez, Sascha Sadewasser, and Marcel S. Claro. "Effect of gallium doping on structural and transport properties of the topological insulator Bi₂Se₃ grown by molecular beam epitaxy." Journal of Applied Physics 132, no. 11 (September 21, 2022): 115107. http://dx.doi.org/10.1063/5.0107004.

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Topological insulators possess non-conductive bulk and present surface states, henceforth, they are electrically conductive along their boundaries. Bismuth selenide (Bi2Se3) is one of the most promising topological insulators. However, a major drawback is its n-type nature arising from its natural doping, which makes the transport in the bulk dominant. This effect can be overcome by shifting the chemical potential into the bandgap, turning the transport of the surface states to be more pronounced than the bulk counterpart. In this work, Bi2Se3 was grown by molecular beam epitaxy and doped with 0.8, 2, 7, and 14 at. % of Ga, with the aim of shifting the chemical potential into the bandgap. The structural, morphological, and electronic properties of the Ga doped Bi2Se3 are studied. Raman and x-ray diffraction measurements confirmed the incorporation of the dopants into the crystal structure. Transport and magnetoresistance measurements in the temperature range of 1.5–300 K show that Ga-doped Bi2Se3 is n-type with a bulk charge carrier concentration of 1019 cm−3. Remarkably, magnetotransport of the weak antilocalization effect measurements confirms the existence of surface states up to a doping percentage of 2 at. % of Ga and coherence length values between 50 and 800 nm, which envisages the possibility of topological superconductivity in this material.

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Prodan, Emil, and Hermann Schulz-Baldes. "Generalized Connes–Chern characters inKK-theory with an application to weak invariants of topological insulators." Reviews in Mathematical Physics 28, no. 10 (November 2016): 1650024. http://dx.doi.org/10.1142/s0129055x16500240.

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We use constructive bounded Kasparov [Formula: see text]-theory to investigate the numerical invariants stemming from the internal Kasparov products [Formula: see text], [Formula: see text], where the last morphism is provided by a tracial state. For the class of properly defined finitely-summable Kasparov [Formula: see text]-cycles, the invariants are given by the pairing of [Formula: see text]-theory of [Formula: see text] with an element of the periodic cyclic cohomology of [Formula: see text], which we call the generalized Connes–Chern character. When [Formula: see text] is a twisted crossed product of [Formula: see text] by [Formula: see text], [Formula: see text], we derive a local formula for the character corresponding to the fundamental class of a properly defined Dirac cycle. Furthermore, when [Formula: see text], with [Formula: see text] the algebra of continuous functions over a disorder configuration space, we show that the numerical invariants are connected to the weak topological invariants of the complex classes of topological insulators, defined in the physics literature. The end products are generalized index theorems for these weak invariants, which enable us to predict the range of the invariants and to identify regimes of strong disorder in which the invariants remain stable. The latter will be reported in a subsequent publication.

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33

Lu, Hai-Zhou, and Shun-Qing Shen. "Weak antilocalization and interaction-induced localization of Dirac and Weyl Fermions in topological insulators and semimetals." Chinese Physics B 25, no. 11 (November 2016): 117202. http://dx.doi.org/10.1088/1674-1056/25/11/117202.

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34

Yue, Zengji, Weiyao Zhao, Kirrily C. Rule, Abuduliken Bake, Lina Sang, Guangsai Yang, Cheng Tan, Zhi Li, Lan Wang, and Xiaolin Wang. "Cross-over from weak localization to anti-localization in rare earth doped TRS protected topological insulators." Physics Letters A 385 (January 2021): 126953. http://dx.doi.org/10.1016/j.physleta.2020.126953.

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35

Muntyanu, Fiodor, Vitalie Chistol, Elena Condrea, and Anatolie Sidorenko. "Topological features of quantum transport in bi_1−xSb_x (0 ≤ x ≤ 0.2) bicrystals." Low Temperature Physics 49, no. 1 (January 2023): 130–35. http://dx.doi.org/10.1063/10.0016486.

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High-quality Bi1− xSb x (0 ≤ x ≤ 0.2) bicrystals with nanowidth crystallite interfaces (CIs), exhibiting simultaneously superconductivity ( Tc ≤ 21 K) and weak ferromagnetism, are studied. A number of unusual features of quantum transport are observed, which are due to topological changes of the Fermi surface of CIs layers, as well as the manifestation of some 3D topological phases of the matter. It is revealed that the flow of Dirac fermions is sensitive to the field orientation, and the localization process occurs only at the B||CIs plane. In doing so, the dependences of the Landau level index n on peak position [Formula: see text] at inclination interfaces are extrapolated to −0.5 if 1 /Bn → 0, as expected for the massless Dirac fermions, while in crystallites and some twisting CIs with an increased degree of imperfection, electronic states are of the Schrodinger type, since n takes integer values. At Sb concentrations of x ∼ 0.04, the high-field thermomagnetic phenomena of CI layers exhibit behavior of the 3D topological semimetals, whereas in bicrystals with 0.07 ≤ x ≤ 0.2 they manifest typical features of the 3D topological insulators.

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36

Tajik, Fatemeh, Zahra Babamahdi, Mehdi Sedighi, and George Palasantzas. "Nonlinear Actuation of Casimir Oscillators toward Chaos: Comparison of Topological Insulators and Metals." Universe 7, no. 5 (April 29, 2021): 123. http://dx.doi.org/10.3390/universe7050123.

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In the current study, we explore the sensitivity of the actuation dynamics of electromechanical systems on novel materials, e.g., Bi2Se3, which is a well-known 3D Topological Insulator (TI), and compare their response to metallic conductors, e.g., Au, that are currently used in devices. Bifurcation and phase portraits analysis in conservative systems suggest that the strong difference between the conduction states of Bi2Se3 and Au yields sufficiently weaker Casimir force to enhance stable operation. Furthermore, for nonconservative driven systems, the Melnikov function and Poincare portrait analysis probed the occurrence of chaotic behavior leading to increased risk for stiction. It was found that the presence of the TI enhanced stable operation against chaotic behavior over a significantly wider range of operation conditions in comparison to typical metallic conductors. Therefore, the use of TIs can allow sufficient surface conductance to apply electrostatic compensation of residual contact potentials and, at the same time, to yield sufficiently weak Casimir forces favoring long-term stable actuation dynamics against chaotic behavior.

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37

Hatsuda, K., H. Mine, T. Nakamura, J. Li, R. Wu, S. Katsumoto, and J. Haruyama. "Evidence for a quantum spin Hall phase in graphene decorated with Bi2Te3 nanoparticles." Science Advances 4, no. 11 (November 2018): eaau6915. http://dx.doi.org/10.1126/sciadv.aau6915.

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Realization of the quantum spin Hall effect in graphene devices has remained an outstanding challenge dating back to the inception of the field of topological insulators. Graphene’s exceptionally weak spin-orbit coupling—stemming from carbon’s low mass—poses the primary obstacle. We experimentally and theoretically study artificially enhanced spin-orbit coupling in graphene via random decoration with dilute Bi2Te3 nanoparticles. Multiterminal resistance measurements suggest the presence of helical edge states characteristic of a quantum spin Hall phase; the magnetic field and temperature dependence of the resistance peaks, x-ray photoelectron spectra, scanning tunneling spectroscopy, and first-principles calculations further support this scenario. These observations highlight a pathway to spintronics and quantum information applications in graphene-based quantum spin Hall platforms.

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38

Ling, Cuicui, Tianchao Guo, Lin Zhao, Zhidong Hou, and Teng Zhang. "Self-powered high-performance topological crystalline insulators tin selenide/silicon dioxide/silicon heterojunction broadband photodetectors for weak signal detection." Ceramics International 45, no. 10 (July 2019): 13275–82. http://dx.doi.org/10.1016/j.ceramint.2019.04.017.

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39

Singh, Shiva Kumar, Julian Munevar, Letície Mendonça-Ferreira, and Marcos A. Avila. "Next-Generation Quantum Materials for Thermoelectric Energy Conversion." Crystals 13, no. 7 (July 21, 2023): 1139. http://dx.doi.org/10.3390/cryst13071139.

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This review presents the recent advances in the search for thermoelectric (TE) materials, mostly among intermetallic compounds and in the enhancement of their TE performance. Herein, contemporary approaches towards improving the efficiency of heat–electricity conversion (e.g., energy harvesting and heat pumping) are discussed through the understanding of various emergent physical mechanisms. The strategies for decoupling the individual TE parameters, as well as the simultaneous enhancement of the TE power factor and the suppression of heat conduction, are described for nanoparticle-doped materials, high entropy alloys, and nanowires. The achievement of a superior TE performance due to emergent quantum phenomena is discussed for intermetallic chalcogenides and related systems (e.g., strong and weak topological insulators, Weyl and Dirac semimetals), and some of the most promising compounds within these classes are highlighted. It was concluded that high-entropy alloying provides a methodological breakthrough for employing band engineering methods along with various phonon scattering mechanisms towards significant TE efficiency improvement in conventional TE materials. Finally, topological semimetals and magnetic semimetals with several intriguing features, such as a violation of the Wiedemann–Franz law and outstanding perpendicular Nernst signals, are presented as strong candidates for becoming next-generation TE quantum materials.

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40

Sahoo, M., Z. Salman, G. Allodi, A. Isaeva, L. Folkers, AUB Wolter, B. Büchner, and R. De Renzi. "Impact of Mn-Pn intermixing on magnetic properties of an intrinsic magnetic topological insulator: the µSR perspective." Journal of Physics: Conference Series 2462, no. 1 (March 1, 2023): 012040. http://dx.doi.org/10.1088/1742-6596/2462/1/012040.

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Abstract We investigated the magnetic properties of polycrystalline samples of the intrinsic magnetic topological insulators MnPn2Te4, with pnictogen Pn = Sb, Bi, by bulk magnetization and µSR. DC susceptibility detects the onset of magnetic ordering at TN = 27 K and 24 K and a field dependence of the macroscopic magnetization compatible with ferri- (or ferro-) and atiferro- magnetic ordering, respectively. Weak transverse field (wTF) Muon Spin Rotation (µSR) confirms the homogeneous bulk nature of magnetic ordering at the same two distinct transition temperatures. Zero Field (ZF) µSR shows that the Sb based material displays a broader distribution of internal field at the muon, in accordance with a larger deviation from the stoichiomectric composition and a higher degree of positional disorder (Mn at the Pn(6c) site), which however does not affect significantly the sharpness of the thermodynamic transition, as detected by the muon magnetic volume fraction and the observability of a critical divergence in the longitudinal and transverse muon relaxation rates.

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41

Zhang, Min, Li Lv, Zhantao Wei, Liqin Yang, Xinsheng Yang, and Yong Zhao. "Electrical and magnetic transport properties of Co-doped Bi2Se3 topological insulator crystals." International Journal of Modern Physics B 28, no. 17 (May 29, 2014): 1450108. http://dx.doi.org/10.1142/s0217979214501082.

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Transition metal doped topological insulators (TI) Co x Bi 2-x Se 3 were prepared and the phase structure, electrical and magnetic transport properties, Hall mobility and Hall resistivity were studied. The lattice constant c decreased with the increasing Co concentration. All samples exhibited weak metallic resistivity. With increasing Co concentration, the value of ρxx increased, reaching a maximum at x = 0.02, and then decreased. The resistivity data could be fitted by different formulas below and above 30 K in all samples result from different mechanism corresponding to different temperature regions. The magnetoresistance (MR) of Bi 2 Se 3 TI showed a change dependence of concentration. The MR was enhanced by small quantity of Co doping, attaining a maximum value in Bi 1.98 Co 0.02 Se 3 crystal; but MR was suppressed in high-doped sample (x > 0.02). Those results were ascribed to the rivalry between the phonon scattering effect and the magnetic ordering in single crystals caused by Co ions. For low-doped samples doped, the contribution of phonon scattering was much higher than that of magnetic ordering, leading to larger MR value. However, in samples doped with higher Co concentrations, the magnetic ordering effect became dominant and caused the MR decreases. The MR increased with decreasing temperature and increasing magnetic field. The Hall mobility data indicated that incorporating Co in Bi 2 Se 3 single crystal can reduce native defect of Bi 2 Se 3.

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42

Zhong, Jingyuan, Ming Yang, Zhijian Shi, Yaqi Li, Dan Mu, Yundan Liu, Ningyan Cheng, et al. "Towards layer-selective quantum spin hall channels in weak topological insulator Bi4Br2I2." Nature Communications 14, no. 1 (August 16, 2023). http://dx.doi.org/10.1038/s41467-023-40735-7.

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AbstractWeak topological insulators, constructed by stacking quantum spin Hall insulators with weak interlayer coupling, offer promising quantum electronic applications through topologically non-trivial edge channels. However, the currently available weak topological insulators are stacks of the same quantum spin Hall layer with translational symmetry in the out-of-plane direction—leading to the absence of the channel degree of freedom for edge states. Here, we study a candidate weak topological insulator, Bi4Br2I2, which is alternately stacked by three different quantum spin Hall insulators, each with tunable topologically non-trivial edge states. Our angle-resolved photoemission spectroscopy and first-principles calculations show that an energy gap opens at the crossing points of different Dirac cones correlated with different layers due to the interlayer interaction. This is essential to achieve the tunability of topological edge states as controlled by varying the chemical potential. Our work offers a perspective for the construction of tunable quantized conductance devices for future spintronic applications.

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Sbierski, Björn, Martin Schneider, and Piet W. Brouwer. "Weak side of strong topological insulators." Physical Review B 93, no. 16 (April 11, 2016). http://dx.doi.org/10.1103/physrevb.93.161105.

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44

Kobayashi, Koji, Tomi Ohtsuki, and Ken-Ichiro Imura. "Disordered Weak and Strong Topological Insulators." Physical Review Letters 110, no. 23 (June 5, 2013). http://dx.doi.org/10.1103/physrevlett.110.236803.

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45

Ringel, Zohar, Yaacov E. Kraus, and Ady Stern. "Strong side of weak topological insulators." Physical Review B 86, no. 4 (July 2, 2012). http://dx.doi.org/10.1103/physrevb.86.045102.

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46

Zhang, Peng, Ryo Noguchi, Kenta Kuroda, Chun Lin, Kaishu Kawaguchi, Koichiro Yaji, Ayumi Harasawa, et al. "Observation and control of the weak topological insulator state in ZrTe5." Nature Communications 12, no. 1 (January 18, 2021). http://dx.doi.org/10.1038/s41467-020-20564-8.

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AbstractA quantum spin Hall (QSH) insulator hosts topological states at the one-dimensional (1D) edge, along which backscattering by nonmagnetic impurities is strictly prohibited. Its 3D analogue, a weak topological insulator (WTI), possesses similar quasi-1D topological states confined at side surfaces. The enhanced confinement could provide a route for dissipationless current and better advantages for applications relative to strong topological insulators (STIs). However, the topological side surface is usually not cleavable and is thus hard to observe. Here, we visualize the topological states of the WTI candidate ZrTe5by spin and angle-resolved photoemission spectroscopy (ARPES): a quasi-1D band with spin-momentum locking was revealed on the side surface. We further demonstrate that the bulk band gap is controlled by external strain, realizing a more stable WTI state or an ideal Dirac semimetal (DS) state. The highly directional spin-current and the tunable band gap in ZrTe5will provide an excellent platform for applications.

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47

Luo, Xun-Jiang, Xiao-Hong Pan, and Xin Liu. "Higher-order topological superconductors based on weak topological insulators." Physical Review B 104, no. 10 (September 22, 2021). http://dx.doi.org/10.1103/physrevb.104.104510.

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48

Cheng, Erjian, Xianbiao Shi, Limin Yan, Tianheng Huang, Fengliang Liu, Wenlong Ma, Zeji Wang, et al. "Critical topology and pressure-induced superconductivity in the van der Waals compound AuTe2Br." npj Quantum Materials 7, no. 1 (September 17, 2022). http://dx.doi.org/10.1038/s41535-022-00499-7.

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AbstractThe study on quantum spin Hall effect and topological insulators formed the prologue to the surge of research activities in topological materials in the past decade. Compared to intricately engineered quantum wells, three-dimensional weak topological insulators provide a natural route to the quantum spin Hall effect, due to the adiabatic connection between them and a stack of quantum spin Hall insulators, and the convenience in exfoliation of samples associated with their van der Waals-type structure. Despite these advantages, both theoretical prediction and experimental identification of weak topological insulators remain scarce. Here, based on first-principles calculations, we show that AuTe2Br locates at the boundary between a strong and a weak topological semimetal state. We identify the key structural parameter that dictates the traversal of the topological transition, which can be easily realized in experiments. More interestingly, the critical topology of AuTe2Br persists up to an applied pressure of ~15.4 GPa before a structural phase transition accompanied by a change of electronic topology and the onset of superconductivity. Our results establish AuTe2Br as a new candidate for an effective tuning between weak and strong topological phases in a single material, with the potential to realize various other topological phases of matter.

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49

Phutela, Ankita, Preeti Bhumla, Manjari Jain, and Saswata Bhattacharya. "Exploring strong and weak topological states on isostructural substitutions in TlBiSe$$_2$$." Scientific Reports 12, no. 1 (December 20, 2022). http://dx.doi.org/10.1038/s41598-022-26445-y.

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AbstractTopological Insulators (TIs) are unique materials where insulating bulk hosts linearly dispersing surface states protected by the Time-Reversal Symmetry. These states lead to dissipationless current flow, which makes this class of materials highly promising for spintronic applications. Here, we predict TIs by employing state-of-the-art first-principles based methodologies, viz., density functional theory and many-body perturbation theory (G$$_0$$ 0 W$$_0$$ 0 ) combined with spin-orbit coupling effects. For this, we take a well-known 3D TI, TlBiSe$$_2$$ 2 and perform complete substitution with suitable materials at different sites to check if the obtained isostructural materials exhibit topological properties. Subsequently, we scan these materials based on SOC-induced parity inversion at Time-Reversal Invariant Momenta. Later, to confirm the topological nature of selected materials, we plot their surface states along with calculation of Z$$_2$$ 2 invariants. Our results show that GaBiSe$$_2$$ 2 is a strong Topological Insulator, besides, we report six weak Topological Insulators, viz., PbBiSe$$_2$$ 2 , SnBiSe$$_2$$ 2 , SbBiSe$$_2$$ 2 , Bi$$_2$$ 2 Se$$_2$$ 2 , TlSnSe$$_2$$ 2 and PbSbSe$$_2$$ 2 . We have further verified that all the reported TIs are dynamically stable, showing all real phonon modes of vibration.

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Yang, Gang, Junwei Liu, Liang Fu, Wenhui Duan, and Chaoxing Liu. "Weak topological insulators in PbTe/SnTe superlattices." Physical Review B 89, no. 8 (February 24, 2014). http://dx.doi.org/10.1103/physrevb.89.085312.

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