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Artykuły w czasopismach na temat "Quantum Spin-orbital Liquid State"
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Katayama, Naoyuki, Kenta Kimura, Yibo Han, Joji Nasu, Natalia Drichko, Yoshiki Nakanishi, Mario Halim i in. "Absence of Jahn−Teller transition in the hexagonal Ba3CuSb2O9 single crystal". Proceedings of the National Academy of Sciences 112, nr 30 (13.07.2015): 9305–9. http://dx.doi.org/10.1073/pnas.1508941112.
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With decreasing temperature, liquids generally freeze into a solid state, losing entropy in the process. However, exceptions to this trend exist, such as quantum liquids, which may remain unfrozen down to absolute zero owing to strong quantum entanglement effects that stabilize a disordered state with zero entropy. Examples of such liquids include Bose−Einstein condensation of cold atoms, superconductivity, quantum Hall state of electron systems, and quantum spin liquid state in the frustrated magnets. Moreover, recent studies have clarified the possibility of another exotic quantum liquid state based on the spin–orbital entanglement in FeSc2S4. To confirm this exotic ground state, experiments based on single-crystalline samples are essential. However, no such single-crystal study has been reported to date. Here, we report, to our knowledge, the first single-crystal study on the spin–orbital liquid candidate, 6H-Ba3CuSb2O9, and we have confirmed the absence of an orbital frozen state. In strongly correlated electron systems, orbital ordering usually appears at high temperatures in a process accompanied by a lattice deformation, called a static Jahn−Teller distortion. By combining synchrotron X-ray diffraction, electron spin resonance, Raman spectroscopy, and ultrasound measurements, we find that the static Jahn−Teller distortion is absent in the present material, which indicates that orbital ordering is suppressed down to the lowest temperatures measured. We discuss how such an unusual feature is realized with the help of spin degree of freedom, leading to a spin–orbital entangled quantum liquid state.
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Nirmala, R., Kwang-Hyun Jang, Hasung Sim, Hwanbeom Cho, Junghwan Lee, Nam-Geun Yang, Seongsu Lee i in. "Spin glass behavior in frustrated quantum spin system CuAl2O4with a possible orbital liquid state". Journal of Physics: Condensed Matter 29, nr 13 (15.02.2017): 13LT01. http://dx.doi.org/10.1088/1361-648x/aa5c72.
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Broholm, C., R. J. Cava, S. A. Kivelson, D. G. Nocera, M. R. Norman i T. Senthil. "Quantum spin liquids". Science 367, nr 6475 (16.01.2020): eaay0668. http://dx.doi.org/10.1126/science.aay0668.
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Spin liquids are quantum phases of matter with a variety of unusual features arising from their topological character, including “fractionalization”—elementary excitations that behave as fractions of an electron. Although there is not yet universally accepted experimental evidence that establishes that any single material has a spin liquid ground state, in the past few years a number of materials have been shown to exhibit distinctive properties that are expected of a quantum spin liquid. Here, we review theoretical and experimental progress in this area.
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Zhu, W., Shou-shu Gong i D. N. Sheng. "Identifying spinon excitations from dynamic structure factor of spin-1/2 Heisenberg antiferromagnet on the Kagome lattice". Proceedings of the National Academy of Sciences 116, nr 12 (4.03.2019): 5437–41. http://dx.doi.org/10.1073/pnas.1807840116.
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A spin-1/2lattice Heisenberg Kagome antiferromagnet (KAFM) is a prototypical frustrated quantum magnet, which exhibits exotic quantum spin liquids that evade long-range magnetic order due to the interplay between quantum fluctuation and geometric frustration. So far, the main focus has remained on the ground-state properties; however, the theoretical consensus regarding the magnetic excitations is limited. Here, we study the dynamic spin structure factor (DSSF) of the KAFM by means of the density matrix renormalization group. By comparison with the well-defined magnetically ordered state and the chiral spin liquid sitting nearby in the phase diagram, the KAFM with nearest neighbor interactions shows distinct dynamical responses. The DSSF displays important spectral intensity predominantly in the low-frequency region around theQ=Mpoint in momentum space and shows a broad spectral distribution in the high-frequency region for momenta along the boundary of the extended Brillouin zone. The excitation continuum identified from momentum- and energy-resolved DSSF signals emergent spinons carrying fractional quantum numbers. These results capture the main observations in the inelastic neutron scattering measurements of herbertsmithite and indicate the spin liquid nature of the ground state. By tracking the DSSF across quantum-phase transition between the chiral spin liquid and the magnetically ordered phase, we identify the condensation of two-spinon bound state driving the quantum-phase transition.
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Oguri, A., K. Yamanaka, J. Inoue i S. Maekawa. "Quantum spin-liquid state with a hole". Physical Review B 43, nr 1 (1.01.1991): 186–92. http://dx.doi.org/10.1103/physrevb.43.186.
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Calvera, Vladimir, Steven A. Kivelson i Erez Berg. "Pseudo-spin order of Wigner crystals in multi-valley electron gases". Low Temperature Physics 49, nr 6 (1.06.2023): 679–700. http://dx.doi.org/10.1063/10.0019425.
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We study multi-valley electron gases in the low density (rs ≫ 1) limit. Here the ground-state is always a Wigner crystal (WC), with additional pseudo-spin order where the pseudo-spins are related to valley occupancies. Depending on the symmetries of the host semiconductor and the values of the parameters such as the anisotropy of the effective mass tensors, we find a striped or chiral pseudo-spin antiferromagnet, or a time-reversal symmetry breaking orbital loop-current ordered pseudo-spin ferromagnet. Our theory applies to the recently-discovered WC states in AlAs and in mono and bilayer transition metal dichalcogenides. We identify a set of interesting electronic liquid crystalline phases that could arise by continuous quantum melting of such WCs.
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Takatsu, Hiroshi, Hiroaki Kadowaki, Taku J. Sato, Jeffrey W. Lynn, Yoshikazu Tabata, Teruo Yamazaki i Kazuyuki Matsuhira. "Quantum spin fluctuations in the spin-liquid state of Tb2Ti2O7". Journal of Physics: Condensed Matter 24, nr 5 (7.12.2011): 052201. http://dx.doi.org/10.1088/0953-8984/24/5/052201.
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Falson, Joseph, Daniela Tabrea, Ding Zhang, Inti Sodemann, Yusuke Kozuka, Atsushi Tsukazaki, Masashi Kawasaki, Klaus von Klitzing i Jurgen H. Smet. "A cascade of phase transitions in an orbitally mixed half-filled Landau level". Science Advances 4, nr 9 (wrzesień 2018): eaat8742. http://dx.doi.org/10.1126/sciadv.aat8742.
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Half-filled Landau levels host an emergent Fermi liquid that displays instability toward pairing, culminating in a gapped even-denominator fractional quantum Hall ground state. While this pairing may be probed by tuning the polarization of carriers in competing orbital and spin degrees of freedom, sufficiently high quality platforms offering such tunability remain few. We explore the ground states at filling factor ν = 5/2 in ZnO-based two-dimensional electron systems through a forced intersection of opposing spin branches of Landau levels taking quantum numbers N = 1 and 0. We reveal a cascade of phases with distinct magnetotransport features including a gapped phase polarized in the N = 1 level and a compressible phase in N = 0, along with an unexpected Fermi liquid, a second gapped, and a strongly anisotropic nematic-like phase at intermediate polarizations when the levels are near degeneracy. The phase diagram is produced by analyzing the proximity of the intersecting levels and highlights the excellent reproducibility and controllability that ZnO offers for exploring exotic fractionalized electronic phases.
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Hashimoto, Akihiro, Yuta Murakami i Akihisa Koga. "Majorana excitations in the anisotropic Kitaev model with an ordered-flux structure". Journal of Physics: Conference Series 2164, nr 1 (1.03.2022): 012028. http://dx.doi.org/10.1088/1742-6596/2164/1/012028.
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Abstract We investigate the anisotropic S = 1/2 Kitaev model on the honeycomb lattice with the ordered-flux structure. By diagonalizing the Majorana Hamiltonian for the flux configuration, we find two distinct gapped quantum spin liquids. One of them is the gapped state realized in the large anisotropic case, where low energy properties are described by the toric code. On the other hand, when the system has small anisotropy, the other gapped quantum spin liquid is stabilized by the ordered-flux configuration. Since these two gapped quantum spin liquids are separated by the gapless region, these are not adiabatically connected to each other.
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Tsvelik, A. M. "New fermionic description of quantum spin liquid state". Physical Review Letters 69, nr 14 (5.10.1992): 2142–44. http://dx.doi.org/10.1103/physrevlett.69.2142.
Pełny tekst źródłaRozprawy doktorskie na temat "Quantum Spin-orbital Liquid State"
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Kermarrec, Edwin. "Nouveaux états quantiques de spin induits par frustration magnétique sur le réseau kagome". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00783605.
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La déstabilisation de l'ordre antiferromagnétique de Néel au profit de nouvelles phases quantiques à température nulle à deux dimensions est envisageable grâce au phénomène de frustration magnétique. Le modèle théorique de spins Heisenberg S=1/2 répartis sur le réseau bidimensionnel frustré kagome, constitué de triangles joints uniquement par leurs sommets, est susceptible de stabiliser des phases quantiques originales de liquides de spin, qui ne présentent aucune brisure de symétrie à T = 0. Cette thèse a été consacrée à l'étude expérimentale de deux types de composés de spins S=1/2 (Cu2+) à géométrie kagome à l'aide de techniques spectroscopiques locales, la RMN et la μSR, ainsi que de mesures thermodynamiques (susceptibilité magnétique, chaleur spécifique). Dans Mg-herbertsmithite, la frustration est générée par une interaction d'échange premiers voisins antiferromagnétique J et est responsable d'un comportement liquide de spin jusqu'à des températures de l'ordre de J/10000. Par rapport au composé isostructural antérieur, Zn-herbertsmithite, nous avons montré qu'il possédait des propriétés physiques similaires tout en permettant une caractérisation fine du taux de défauts de substitutions Cu/Mg. Nos expériences réalisées à partir d'échantillons contrôlés permettent d'étudier finement l'origine des plateaux de relaxation observés en μSR à basse température en lien avec l'existence des défauts de spins interplans. La kapellasite et l'haydéite possèdent des interactions ferromagnétiques (J1) et antiferromagnétiques (Jd), offrant la possibilité d'explorer le diagramme de phases générées par la compétition de ces interactions sur le réseau kagome. Pour la kapellasite, nos mesures de μSR démontrent le caractère liquide de spin jusqu'à T ≈ J1/1000. La dépendance en température de la susceptibilité magnétique sondée par RMN du 35Cl ainsi que de la chaleur spécifique permettent d'évaluer le rapport Jd/J1 = 0.85, qui localise classiquement son fondamental au sein d'une phase originale de spins non coplanaires à 12 sous-réseaux appelée cuboc2. Les interactions présentes dans l'haydéite localisent son fondamental au sein de la phase ferromagnétique, en bon accord avec nos mesures qui indiquent une transition partielle à caractère ferromagnétique à T = 4 K. Cette étude confirme la pertinence du réseau kagome frustré pour la stabilisation de phases quantiques originales et démontre l'existence d'une nouvelle phase liquide de spin sur ce réseau, distincte de celle attendue pour des spins couplés antiferromagnétiquement.
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Wu, Kai-Hsin, i 吳愷訢. "Classical spin liquid state in quantum kagome ice". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/m754e2.
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碩士國立臺灣大學
物理學研究所
106
We study the spin-1/2 Heisenberg XYZh model on a kagome lattice with quantum Monte Carlo (QMC) simulation. Recently, the model is proposed to host the Z2 quantum spin liquid (QSL) with a Z2 topological order. Numerical studies found a quantum kagome ice state which lacks long-range order. This suggests the possibility for the state to be a Z2 QSL. However, no direct evidence of Z2 QSL is shown. Here, we carefully examine the XYZh model. By measuring the topological entanglement entropy using quantum Monte Carlo simulation, we find that, contrary to previous beliefs, the state has no Z2 topological order. Instead, the system behaves like a classical kagome ice down to a very low temperature. Our theoretical analysis indicates that an intricate competition of the off-diagonal and non-trivial diagonal perturbation contributions suppresses the quantum energy scale. This leads to a quasi-degenerate picture where the system remains classical. The scenario is supported with the measurement of hexagon fractions using QMC. This is a rare example of a quantum model that remains classical down to a very low temperature that is due to quantum tunneling effect. The mechanism opens a way to engineer quantum-to-classical crossover in quantum magnets.
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Hossain, Akmal. "Investigation of strongly correlated paramagnetic state at sub-Kelvin regime for S ≥ 1/2 systems: Role of disorder and dimensionality". Thesis, 2022. https://etd.iisc.ac.in/handle/2005/6061.
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A magnetic system usually orders ferro- or anti-ferromagnetically at temperatures
comparable to interaction strength between the spins. Moreover, an interacting
spin system tends to order with the increase of dimensionality of the magnetic lattice,
as determined by the spin-spin correlation along various directions. However, there
are certain lattice types where such orderings are strongly suppressed. A prototypical
example is the Ising spin-1/2 on a triangular lattice with a nearest neighbour antiferromagnetic
interaction where the triangular arrangement results in competing interactions
leading to a large number of distinct states with the same ground state energy
and therefore magnetic frustration. When frustration extends over a long range, it
can lead to the formation of highly degenerate ground states with spin fluctuations at
absolute zero temperature, leading to exotic magnetic ground states such as Quantum
Spin Liquid (QSL). In recent times, there is an increasing interest in such magnetically
frustrated systems, in search of QSLs which relieve the frustration by entangling
the spins instead of ordering. Another approach to achieve a ground state without ordering
is to introduce sufficient magnetic disorder in a lattice. Such systems may get
stuck in a differently disordered “glassy” state. In this thesis work, we explore what
happens when extensive disorder is in the frustrated triangular lattice such that conditions
that promote spin liquid coexist with those aiding glassiness. The thesis will
present in detail such dynamic correlated paramagnetic states in a few selected materials.
These systems differ, not only in their chemical compositions and the nature of
the magnetic ions, but also in terms of the dimensionality of the magnetic interactions
and the extent of disorder.
Using combined experimental and theoretical approaches,
detailed investigations have been carried out on a series of magnetic materials,
varying the extent of disorder, dimensionality of magnetic interactions, and the
magnetic spin moments, at the sub-Kelvin temperature regime, revealing several unexpected
behaviours.
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Puetter, Christoph Minol. "Emergent Low Temperature Phases in Strongly Correlated Multi-orbital and Cold Atom Systems". Thesis, 2012. http://hdl.handle.net/1807/32317.
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This thesis considers various strongly correlated quantum phases in solid state and cold atom spin systems.
In the first part we focus on phases emerging in multi-orbital materials.
We study even-parity spin-triplet superconductivity originating from Hund's coupling between t2g orbitals and investigate the effect of spin-orbit interaction on spin-triplet and spin-singlet pairing.
Various aspects of the pairing state are discussed against the backdrop of the spin-triplet superconductor Sr2RuO4.
Motivated by the remarkable phenomena observed in the bilayer compound Sr3Ru2O7, which point to the formation of an electronic nematic phase in the presence of critical fluctuations, we investigate how such a broken symmetry state emerges from electronic interactions.
Since the broken x-y symmetry is revealed experimentally by applying a small in-plane
magnetic field component, we examine nematic phases in a bilayer system and the role of the in-plane magnetic field using a phenomenological approach.
In addition, we propose a microscopic mechanism for nematic phase formation
specific to Sr3Ru2O7.
The model is based on a realistic multi-orbital band structure and local and nearest neighbour interactions.
Considering all t2g-orbital derived bands on an equal footing, we find a nematic quantum critical point and a nearby meta-nematic transition in the phase diagram.
This finding harbours important implications for the phenomena observed in Sr3Ru2O7.
The second part is devoted to the study of the anisotropic bilinear biquadratic spin-1 Heisenberg model, where the existence of an unusual direct phase transition between a spin-nematic phase and a dimerized valence bond solid phase in the quasi-1D limit was conjectured based on Quantum Monte Carlo simulations.
We establish the quasi-1D phase diagram using a large-N Schwinger boson approach and show that the phase transition is largely conventional except possibly at two particular points.
We further discuss how to realize and to detect such phases in an optical lattice.
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Mandal, Shoubhik. "Electrical transport and optical studies of spin-orbit coupled topological phases in different correlation regimes". Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5732.
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The interplay of spin-orbit coupling (SOC) and electron-electron correlation in different regimes gave birth to many novel topological phases with exotic properties ranging from quantum transport to superconductivity. One of those phases, topological insulators(TI), attract attention widely due to its promising potential in building next-generation quantum computers. Strong TI (for example, Bi2Se3, BiSbTeSe, etc.), the most popular subclass of TI, has been investigated extensively. Recently, another subclass of TI known as a dual topological insulator(DTI) is being realized as new material. One of the examples of DTI is Bi1Te1, recently discovered as a topological system to host a weak TI state on the sides and topological crystalline insulating (TCI) state on the remaining surfaces. On the contrary, quantum spin liquid (QSL), another new topological phase, emerges due to strong electron-electron correlation. Honeycomb material RuCl3 has been studied as a quantum spin liquid candidate combining the Kitaev model and Jackeli-Khaliullin theory.
In the 1st work, we synthesized the single crystals of pure Bi1Te1 and Sb-doped Bi1Te1 (Bi0.88Sb0.05Te1) via the modified Bridgmann method. After characterizing the single crystal by XRD, Raman spectroscopy, XPS, and EPMA, we investigated the electrical transport properties of the devices fabricated out of nanoflakes exfoliated from the as-grown crystals in the presence of out-of-plane and in-plane magnetic fields. We observed weak anti-localization (WAL), an important feature in low-field magneto-conductance to quantify the coherently conducting surface states. We analyzed WAL using Hikami-Larkin-Nagaoka equation. The phase coherence length (Lϕ) vs. T indicates the dephasing mechanism via 2D electron-phonon interaction in both cases: pure Bi1Te1 and Sb-doped Bi1Te1. With increasing thickness of the nanodevice, the dominance of the electron-phonon interaction increases. Hall effect further confirms the negative sign of the majority charge carriers and yields carrier density and mobility for both the crystals. The change in the parameters from the Hall effect is not noticeable much. In-plane field transport gives more information about the intermixing of the surface states with the bulk states owing to defects in Sb-doped system.
In the second work, we mainly investigated the optical properties of Kitaev spin liquid candidate RuCl3 via steady-state and time-resolved photoluminescence (PL) and Raman spectroscopy. We have grown RuCl3 via the physical vapor transport technique. We characterized as-grown crystals via XRD, EPMA, and magnetic measurement, confirming the antiferromagnetic transitions at 8 K and 15 K. We evaluated the bandgap to be 1.9 eV, indicating the Mott insulating properties of RuCl3. We explained the PL spectra obtained from the bulk RuCl3 and nanoflake in terms of the Tanabe-Suagno diagram, useful to describe the optical transition in a strongly correlated system with an octahedral crystal structure. Electrical transport on RuCl3 was also carried out in bulk and the thin-film limit. R ~ T curve indicates 2D variable range hopping transport and has a feature at 170 K owing to structural transition.
In the third work, we investigated the electrical transport properties of strong 3D TI Bi1Sb1Te1.5Se1.5 coupled to RuCl3. Since RuCl3 is a Mott insulator, we carried out the electrical measurement on the BSTS flake only. We fabricated the BSTS/RuCl3 heterostructure via the hot, dry transfer method in Argon-filled Glove Box followed by e-beam lithography. We extracted information from the perpendicular and in-plane field transport measurement indicating the presence of topological surface states (TSS) and Rashba surface states (RSS). We observed for thicker RuCl3 ( ≥ 100 nm), RSS is well separated from TSS underneath the RuCl3 layer. This effect is clearly visible in the values of the change in the slope in logarithmic temperature-dependence of the sheet conductance plot. This phenomenon is explained in terms of charge transfer from RuCl3 to the BSTS surface layer, causing stronger band bending.DST, Nanomission
Książki na temat "Quantum Spin-orbital Liquid State"
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Eriksson, Olle, Anders Bergman, Lars Bergqvist i Johan Hellsvik. Atomistic Spin Dynamics. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198788669.001.0001.
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The purpose of this book is to provide a theoretical foundation and an understanding of atomistic spin-dynamics, and to give examples of where the atomistic Landau-Lifshitz-Gilbert equation can and should be used. The contents involve a description of density functional theory both from a fundamental viewpoint as well as a practical one, with several examples of how this theory can be used for the evaluation of ground state properties like spin and orbital moments, magnetic form-factors, magnetic anisotropy, Heisenberg exchange parameters, and the Gilbert damping parameter. This book also outlines how interatomic exchange interactions are relevant for the effective field used in the temporal evolution of atomistic spins. The equation of motion for atomistic spin-dynamics is derived starting from the quantum mechanical equation of motion of the spin-operator. It is shown that this lead to the atomistic Landau-Lifshitz-Gilbert equation, provided a Born-Oppenheimer-like approximation is made, where the motion of atomic spins is considered slower than that of the electrons. It is also described how finite temperature effects may enter the theory of atomistic spin-dynamics, via Langevin dynamics. Details of the practical implementation of the resulting stochastic differential equation are provided, and several examples illustrating the accuracy and importance of this method are given. Examples are given of how atomistic spin-dynamics reproduce experimental data of magnon dispersion of bulk and thin-film systems, the damping parameter, the formation of skyrmionic states, all-thermal switching motion, and ultrafast magnetization measurements.
Części książek na temat "Quantum Spin-orbital Liquid State"
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Amusia, Miron, i Vasily Shaginyan. "Quantum Spin Liquid in Geometrically Frustrated Magnets and the New State of Matter". W Springer Tracts in Modern Physics, 125–49. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-50359-8_8.
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Lorch, Mark. "How Do We Make Digital Light?" W A Flash of Light: The Science of Light and Colour, 101–11. The Royal Society of Chemistry, 2016. http://dx.doi.org/10.1039/bk9781782627319-00101.
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Gases, liquids and solids are not the only possibilities for states of matter, they aren't even the most common states. Plasma, from which stars are made, is much more dominant. The tremendous temperatures inside stars rips electrons from atoms forming gas-like plasma. What's more, there are many other states with exotic names like Fermionic condensates, superfluids and quantum spin liquids, which occur under a wealth of extreme conditions. Others states are commonplace in the world we inhabit and liquid crystals are one of them. This chapter takes a look at this odd state of matter and how it led to light emitting devices dominating our digital age.
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Autschbach, Jochen. "From Schrödinger to Einstein and Dirac: Relativistic Effects". W Quantum Theory for Chemical Applications, 555–92. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190920807.003.0024.
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The implications of Einstein’s special relativity in chemistry are discussed. It is shown that relativistic effects on the electronic structure of an atom or molecule scales in leading order as Z2, where Z is the charge number of the heaviest nucleus in the system. Well-known heavy atom effects in chemistry are discussed: The color of gold, the liquid state of mercury, the inert pair effect of heavy p-block elements, and more. Spin-orbit coupling (SOC) is also a relativistic effect and plays a big role in spectroscopy and chemistry. The Dirac equation (DE) replaces the electronic Schrodinger equation in relativistic quantum chemistry. The Dirac wavefunctions have 4 components. It is shown how an ‘exact 2-component’ (X2C) Hamiltonian can be constructed. X2C based all-electron calculations are becoming increasingly popular in quantum chemical applications. Molecular properties may undergo a picture-change effect when going from a 4-component to a 2-component framework.
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Stein, Daniel L., i Charles M. Newman. "Magnetic Systems". W Spin Glasses and Complexity. Princeton University Press, 2013. http://dx.doi.org/10.23943/princeton/9780691147338.003.0004.
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The chapter explains that up to this point the discussion has centered on some basic concepts of condensed matter physics as viewed through the illustrative lenses of familiar systems: liquids, crystals, and glasses. The chapter now turns to another important class of materials: magnetic systems, which are regarded as materials possessing properties that can be altered or manipulated through the application of an external magnetic field. The chapter introduces the basics of solid state magnetism, starting with the quantum mechanical property of spin, and showing how the familiar phenomenon of ferromagnetism—as well as the less familiar but equally important ones of antiferromagnetism and paramagnetism—arises. This is a necessary prelude to understanding the idea of what a spin glass is.
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Autschbach, Jochen. "Electron Spin and General Angular Momenta". W Quantum Theory for Chemical Applications, 356–76. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190920807.003.0019.
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The historical background of the discovery of the electron spin is provided. The Stern-Gerlach and Einstein-de Haas experiments are discussed. The operators for a single electron spin are defined, along with the formulation in terms of the 2x2 Pauli matrices. The discussion then moves on to the definition of the spin for many-electron systems and explains how the famous Hund rule (or Hund’s first rule) arises from considering the energy of an open-shell spin singlet vs. triplet state. Next, the generalized angular momentum, ladder operators, and spherical vector operators are defined, and the rules for the addition of angular momenta are derived. The chapter concludes with a discussion of the total spin, orbital, and total angular momentum for open-shell atoms, term symbols, and Hund’s second and third rule.
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Nitzan, Abraham. "The Spin–Boson Model". W Chemical Dynamics in Condensed Phases. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780198529798.003.0018.
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In a generic quantum mechanical description of a molecule interacting with its thermal environment, the molecule is represented as a few level system (in the simplest description just two, for example, ground and excited states) and the environment is often modeled as a bath of harmonic oscillators. The resulting theoretical framework is known as the spin–boson model, a term that seems to have emerged in the Kondo problem literature (which deals with the behavior of magnetic impurities in metals) during the 1960s, but is now used in a much broader context. Indeed, it has become one of the central models of theoretical physics, with applications in physics, chemistry, and biology that range far beyond the subject of this book. Transitions between molecular electronic states coupled to nuclear vibrations, environmental phonons, and photon modes of the radiation field fall within this class of problems. The present chapter discusses this model and some of its mathematical implications. The reader may note that some of the subjects discussed in Chapter 9 are reiterated here in this more general framework. In Sections 2.2 and 2.9 we have discussed the dynamics of the two-level system and of the harmonic oscillator, respectively. These exactly soluble models are often used as prototypes of important classes of physical system. The harmonic oscillator is an exact model for a mode of the radiation field and provides good starting points for describing nuclear motions in molecules and in solid environments. It can also describe the short-time dynamics of liquid environments via the instantaneous normal mode approach. In fact, many linear response treatments in both classical and quantum dynamics lead to harmonic oscillator models: Linear response implies that forces responsible for the return of a system to equilibrium depend linearly on the deviation from equilibrium—a harmonic oscillator property! We will see a specific example of this phenomenology in our discussion of dielectric response in Section 16.9.
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Cao, Gang, i Lance E. DeLong. "Lattice-Driven Ruthenates". W Physics of Spin-Orbit-Coupled Oxides, 102–34. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780199602025.003.0004.
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Ruthenates have extended 4d-electron orbitals and comparable Coulomb, crystalline electric field, and spin-orbit interactions, as well as significant p-d orbital hybridization and spin-lattice coupling. The physical properties of ruthenates are highly susceptible to even slight lattice distortions; as a result, external magnetic field, pressure, electrical current, and chemical doping can generate disproportionate responses in structural as well as other physical properties, which can lead to unusual ground states or phenomena. Examples of the unusual, strong coupling of the ruthenates to external stimuli include negative volume thermal expansion via orbital and magnetic order in doped Ca2RuO4, colossal magnetoresistivity via avoiding a spin-polarized state and quantum oscillations in Ca3Ru2O7, and pressure-induced transition from ferromagnetism to antiferromagnetism in Sr4Ru3O10.
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Dyall, Kenneth G., i Knut Faegri. "Correlation Methods". W Introduction to Relativistic Quantum Chemistry. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195140866.003.0018.
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It is well known from nonrelativistic quantum chemistry that mean-field methods, such as the Hartree–Fock (HF) model, provide mainly qualitative insights into the electronic structure and bonding of molecules. To obtain reliable results of “chemical accuracy” usually requires models that go beyond the mean field and account for electron correlation. There is no reason to expect that the mean-field approach should perform significantly better in this respect for the relativistic case, and so we are led to develop schemes for introducing correlation into our models for relativistic quantum chemistry. There is no fundamental change in the concept of correlation between relativistic and nonrelativistic quantum chemistry: in both cases, correlation describes the difference between a mean-field description, which forms the reference state for the correlation method, and the exact description. We can also define dynamical and nondynamical correlation in both cases. There is in fact no formal difference between a nonrelativistic spin–orbital-based formalism and a relativistic spinor-based formalism. Thus we should be able to transfer most of the schemes for post-Hartree–Fock calculations to a relativistic post-Dirac–Hartree–Fock model. Several such schemes have been implemented and applied in a range of calculations. The main technical differences to consider are those arising from having to deal with integrals that are complex, and the need to replace algorithms that exploit the nonrelativistic spin symmetry by schemes that use time-reversal and double-group symmetry. In addition to these technical differences, however, there are differences of content between relativistic and nonrelativistic methods. The division between dynamical and nondynamical correlation is complicated by the presence of the spin–orbit interaction, which creates near-degeneracies that are not present in the nonrelativistic theory. The existence of the negative-energy states of relativistic theory raise the question of whether they should be included in the correlation treatment. The first two sections of this chapter are devoted to a discussion of these issues. The main challenges in the rest of this chapter are to handle the presence of complex integrals and to exploit time-reversal symmetry.
Streszczenia konferencji na temat "Quantum Spin-orbital Liquid State"
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Kumar, Krishan, Gurvinder Singh i R. K. Moudgil. "Effect of valley degeneracy on spin susceptibility of a two-dimensional quantum electron liquid". W SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4872798.
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Nagashima, Hiroki, Takashi Tokumasu, Shin-ichi Tsuda, Nobuyuki Tsuboi, Mitsuo Koshi i A. Koichi Hayashi. "An Estimation of Thermodynamic and Transport Properties of Cryogenic Hydrogen Using Classical Molecular Simulation". W ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-36005.
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In this paper, we estimated the thermodynamic and transport properties of cryogenic hydrogen using classical molecular simulation to clarify the limit of classical method on the estimation of those properties of cryogenic hydrogen. Three empirical potentials, the Lennard-Jones (LJ) potential, two-center Lennard-Jones (2CLJ) potential, and modified Buckingham (exp-6) potential, and an ab initio potential model derived by the molecular orbital (MO) calculation were applied. Molecular dynamics (MD) simulations were performed across a wide density-temperature range. Using these data, the equation of state (EOS) was obtained by Kataoka’s method, and these were compared with NIST (National Institute of Standards and Technology) data according to the principle of corresponding states. Moreover, we investigated transport coefficients (viscosity coefficient, diffusion coefficient and thermal conductivity) using time correlation function. As a result, it was confirmed that the potential model has a large effect on the estimated thermodynamic and transport properties of cryogenic hydrogen. On the other hand, from the viewpoint of the principle of corresponding states, we obtained the same results from the empirical potential models as from the ab initio potential, showing that the potential model has only a small effect on the reduced EOS: the classical MD results could not reproduce the NIST data in the high-density region. This difference is thought to arise from the quantum effect in actual liquid hydrogen.
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Fuchs, Gregory D. "Quantum Control of Spin and Orbital States with a Diamond MEMS Resonator". W 2021 21st International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers). IEEE, 2021. http://dx.doi.org/10.1109/transducers50396.2021.9495751.
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