Literatura académica sobre el tema "Synthetic spin-orbit coupling"

In this review we will discuss the experimental and theoretical progresses in studying spin–orbit coupled degenerate atomic gases during the last two years. We shall first review a series of pioneering experiments in generating synthetic gauge potentials and spin–orbit coupling in atomic gases by engineering atom-light interaction. Realization of spin–orbit coupled quantum gases opens a new avenue in cold atom physics, and also brings out a lot of new physical problems. In particular, the interplay between spin–orbit coupling and inter-atomic interaction leads to many intriguing phenomena. By reviewing recent theoretical studies of both interacting bosons and fermions with isotropic Rashba spin–orbit coupling, the key message delivered here is that spin–orbit coupling can enhance the interaction effects, and make the interaction effects much more dramatic even in the weakly interacting regime.

Spin-orbit interactions lead to distinctive functionalities in photonic systems. They exploit the analogy between the quantum mechanical description of a complex electronic spin-orbit system and synthetic Hamiltonians derived for the propagation of electromagnetic waves in dedicated spatial structures. We realize an artificial Rashba-Dresselhaus spin-orbit interaction in a liquid crystal–filled optical cavity. Three-dimensional tomography in energy-momentum space enabled us to directly evidence the spin-split photon mode in the presence of an artificial spin-orbit coupling. The effect is observed when two orthogonal linear polarized modes of opposite parity are brought near resonance. Engineering of spin-orbit synthetic Hamiltonians in optical cavities opens the door to photonic emulators of quantum Hamiltonians with internal degrees of freedom.

Abstract The electrical control of a spin qubit in a quantum dot (QD) relies on spin–orbit coupling (SOC), which could be either intrinsic to the underlying crystal lattice or heterostructure, or extrinsic via, for example, a micro-magnet. In experiments, micromagnets have been used as a synthetic SOC to enable strong coupling of a spin qubit in quantum dots with electric fields. Here we study theoretically the spin relaxation, pure dephasing, spin manipulation, and spin–photon coupling of an electron in a QD due to the synthetic SOC induced spin–orbit mixing. We find qualitative difference in the spin dynamics in the presence of a synthetic SOC compared with the case of the intrinsic SOC. Specifically, spin relaxation due to the synthetic SOC and deformation potential phonon emission (or Johnson noise) shows B 0 5 (or B 0) dependence with the magnetic field, which is in contrast with the B 0 7 (or B 0 3 ) dependence in the case of the intrinsic SOC. Moreover, charge noise induces fast spin dephasing to the first order of the synthetic SOC, which is in sharp contrast with the negligible spin pure dephasing in the case of the intrinsic SOC. These qualitative differences are attributed to the broken time-reversal symmetry (T-symmetry) of the synthetic SOC. An SOC with broken T-symmetry (such as the synthetic SOC from a micro-magnet) eliminates the ‘Van Vleck cancellation’ and causes a finite longitudinal spin–electric coupling that allows the longitudinal coupling between spin and electric field, and in turn allows spin pure dephasing. Finally, through proper choice of magnetic field orientation, the electric-dipole spin resonance via the synthetic SOC can be improved with potential applications in spin-based quantum computing.

The concept of synthetic dimensions has generated interest in many branches of science, ranging from ultracold atomic physics to photonics, as it provides a versatile platform for realizing effective gauge potentials and topological physics. Previous experiments have augmented the real-space dimensionality by one additional physical synthetic dimension. In this study, we endow a single ring resonator with two independent physical synthetic dimensions. Our system consists of a temporally modulated ring resonator with spatial coupling between the clockwise and counterclockwise modes, creating a synthetic Hall ladder along the frequency and pseudospin degrees of freedom for photons propagating in the ring. We observe a wide variety of physics, including effective spin-orbit coupling, magnetic fields, spin-momentum locking, a Meissner-to-vortex phase transition, and signatures of topological chiral one-way edge currents, completely in synthetic dimensions. Our experiments demonstrate that higher-dimensional physics can be studied in simple systems by leveraging the concept of multiple simultaneous synthetic dimensions.

In this paper, we study an atomic chain in the presence of modulated charge potential and modulated Rashba spin-orbit coupling (RSOC) of equal periods. We show that for commensurate periodicities, λ = 4 n with integer n, the three-dimensional synthetic space obtained by sliding the two phases of the charge potential and RSOC features a topological nodal-line semimetal protected by an anti-unitary particle-hole symmetry. The location and shape of the nodal lines strongly depend on the relative amplitude between the charge potential and RSOC.

In this article our attempts to tune the color of luminescence within a new class of aggregation-induced emission (AIE) active tellurophenes is reported along with computational details that include spin–orbit coupling effects so as to better understand the nature of emission in the phosphorescent tellurophene (B-Te-6-B). Despite not meeting some of the initial synthetic targets, the emission within a borylated tellurophene can be altered with the addition of an N-heterocyclic carbene.

Cette thèse porte sur l'étude d'oxydes d'iridium dont le fort couplage spin-orbite est susceptible de générer de nouvelles phases électroniques et magnétiques. Deux familles de composés ont été considérées: Sr3MM’O6, à chaines de spins mixtes arrangées sur réseau triangulaire, et R2Ir2O7, à réseaux pyrochlores interpénétrés de spins. Ils ont été synthétisés sous forme polycristalline et pour certains sous forme monocristalline puis étudiés macroscopiquement par mesure d'aimantation. Ils ont ensuite été sondés microscopiquement par diffusion de neutrons et de rayons X. Nos mesures montrent que dans les composés à chaînes de spins Sr3NiPtO6 et Sr3NiIrO6 les ions Ni2+ présentent une très forte anisotropie magnétocristalline planaire perpendiculaire à l'axe des chaînes. Nous démontrons que ceci stabilise dans Sr3NiPtO6 une phase non magnétique dite « large-D ». Cette anisotropie se manifeste dans Sr3NiIrO6 à haute température. Ce composé s'ordonne cependant à basse température dans une structure magnétique avec les moments alignés le long de l'axe des chaînes. Nous expliquons ce changement d'anisotropie comme étant dû à la présence des ions Ir4+ dont le couplage spin-orbite produit une forte anisotropie des interactions Ni-Ir qui confinent les moments magnétiques le long des chaînes. Concernant les pyrochlores iridates R2Ir2O7, les mesures d'aimantation et de diffraction de neutron sont cohérents avec un ordre "all-in/all-out" des moments magnétiques des ions Ir4+, révélé indirectement via le comportement du sous-réseau des terres rares R. Cet ordre est le seul compatible avec la phase semi-métal de Weyl prédite comme résultant du fort couplage spin-orbite. Le comportement du sous-réseau de terre rare R dépend de l'anisotropie magnétocrystalline des ions R3+. Les ions à anisotropie uniaxiale locale sont polarisés par le champ moléculaire produit par l'ordre de l'iridium dont la direction coïncide avec l'axe d'anisotropie. Les ions à anisotropie locale planaire perpendiculaire à cette direction ne présentent pas d’ordre magnétique induit par celui de l'iridium. A plus basse température, les interactions entre terres rares génèrent des comportements magnétiques plus complexes
This thesis focuses on the study of iridium oxides, in particular on the consequences of the strong spin-orbit coupling of the iridium. Two families of compounds have been investigated: Sr3MM’O6, with mixed spin chains arranged on a triangular lattice, and R2Ir2O7 with interpenetrated pyrochlores networks of spins. Polycrystalline samples have been synthetized and in some instances single crystals were successfully grown. They were investigated macroscopically by magnetization measurements and probed microscopically by neutron and synchrotoron X-ray scattering experiments. Our measurements showed that in the spin chain compounds Sr3NiPtO6 and Sr3NiIrO6 the Ni2+ ions show a strong easy plane magnetocrystalline anisotropy, perpendicular to the chain axis. This stabilizes in Sr3NiPtO6 the so-called "large-D" non-magnetic phase. The planar anisotropy comes out in Sr3NiIrO6 at high temperature. The compound however orders at low temperature in a magnetic configuration with all the magnetic moments confined along the chain axis. We explain this change of anisotropy as due to the Ir4+ ions whose spin-orbit coupling produces a strong anisotropy of the intra-chain Ni-Ir magnetic interactions overwhelming the single-ion Ni2+ anisotropy. Concerning the pyrochlore iridates R2Ir2O7, magnetization measurements and neutron powder diffraction experiments are consistent with an "all-in/all-out" magnetic ordering of the Ir magnetic moments, revealed indirectly through the magnetic behavior of the rare-earth sublattice. This ordering is the only one consistent with a Weyl semi-metal phase predicted to arise from the spin-orbit coupling. The magnetic behavior of the rare-earth sublattice depends on the rare earth magnetocrystalline anisotropy. The ions with local uniaxial anisotropy are polarized by the Ir molecular field, whose direction coincides with the anisotropy axis. The ions with local planar anisotropy perpendicular to this direction show no iridium induced long-range magnetic ordering. At lower temperature, rare-earth interactions generate more complex magnetic behaviors

博士
國立清華大學
物理系
104
In this thesis, I will discuss the effect of spin-orbit coupling in different systems: spinor Bose-Einstein Condensate (BEC) system, bilayer Fermionic system, and 2D topological insulator. In the spinor BEC system, I focus on the hybrid effect of spin-orbit coupling and two-body interaction. By using adiabatic approximation, I systematically investigate the ground state, elementary excitations and related effects of a BEC within a synthetic vector potential. In the bilayer Fermionic system, I consider the effect of spin-layer coupling and superfluidity. By mapping to an effective model, I demonstrate that at zero temperature the critical value of the magnetic field for pairing can be significantly increased by including a spin-flip tunnelling between layers. In the 2D topological insulator, I focus on the Kane-Mele (KM) Hubbard model and consider the effect of a single spin-flip impurity at the Zigzag edge. I analytically obtain the spectra and wavefunction of the KM model and then discuss its electronic transport property. Furthermore, I develop a low energy effective 1D model to describe the system.

In this thesis I report on the experimental results obtained during the years of my PhD in the laboratory of the University of Florence devoted to the investigation of quantum degenerate gases of Ytterbium. I discuss the main results that we achieved, focusing the attention on the experiments concerning two main research lines, the first related to the quantum simulation of synthetic gauge fields with ultracold Yb atoms and the second one to the investigation of two-orbital quantum physics exploiting the 1S0->3P0 clock transition. In particular we have been able to unify these fields of research simulating for the first time a synthetic gauge field for neutral atoms exploiting the orbital degree of freedom offered by two-electron atoms. The realization of artificial gauge fields for neutral atoms is a current trend in the context of quantum simulation and several techniques have been proposed and experimentally realized. Here we adopt a recently proposed quantum simulation scheme which relies on the concept of synthetic dimension. In this scheme an internal degree of freedom of the atom is interpreted as an extra dimension of the system and a hybrid 2D ladder is realized combining this synthetic dimension with a real one-dimensional optical lattice. An artificial magnetic field naturally arises in this hybrid 2D lattice as a consequence of the phase imprinted on the atoms by the laser coupling between the synthetic sites. We exploited this scheme in two different experiments with fermionic 173Yb, in which we map the synthetic dimension in the first case on the ground and clock states of the atom and in the second case on the nuclear spin states of the ground level. Couplings between synthetic sites are realized exploiting single-photon clock transitions and two-photon Raman transitions in the first and second experiment respectively. Despite their simplicity these systems feature some fundamental properties of larger quantum Hall bars, one of which is the presence of chiral currents counter-propagating on the synthetic edges. We have been able to induce and detect these chiral currents in ladders characterized by two and three (only in the Raman case) legs. In the case of the clock approach, for which the experimental realization is simpler, we have also been able to tune the artificial magnetic field and characterized for the first time the strength of the currents as a function of the synthetic flux, a result impossible to achieve in real solid-state systems where magnetic fields of the order of several thousand of Tesla would be required. In the three-leg Raman case we have also investigated the dynamics of the system observing the skipping-orbit-like trajectories performed by fermions in the hybrid space after a quenching of the synthetic tunnelling. In another experiment we used the orbital degree of freedom of 173Yb to demonstrate the possibility to implement Spin-Orbit Coupling (SOC) with single-photon clock transitions in a system of fermionic atoms trapped in a one-dimensional optical lattice, using as pseudospin states the fundamental level 1S0 and the clock state 3P0. This orbital approach to the synthesis of SOC in ultracold gases allows us to overcome some of the limitations imposed by Raman schemes in alkali atoms, where heating due to the presence of intermediate levels has detrimental effects in the observation of many-body processes. The emergence of SOC is detected by evaluating the broadening of the clock spectroscopic response which results from transitions connecting states with different lattice quasimomentum. Our ability to observe these narrow features relies on the high spectroscopic resolution of our clock laser system and is enabled by the long-term stabilization of the laser frequency on the metrological reference delivered by INRiM (the Italian metrological institute) from Turin to Florence through a 642-km-long fiber link. Remarkably, exploiting the long term accuracy provided by the fiber link, we have been able to improve the absolute value of the clock transition in 173Yb by two orders of magnitude with respect to the value previously reported in literature. We exploited the orbital degree of freeedom of 173Yb also to realize a new kind of Feshbach resonance which allows for the tuning of the scattering properties in a mixture of atoms in different orbital states. The possibility to tune interactions by means of standard Feshbach resonances lacked in two-electron atoms due to the absence of a hyperfine structure in the fundamental state. We instead experimentally demonstrated how a similar mechanism is possible also for this class of elements provided that atoms in two different electronic states are considered. In particular, we exploited the orbital Feshbach resonance mechanism to realize a strongly interacting two-orbital gas of 173Yb and characterized the resonance position evaluating the hydrodynamic expansion of the gas. The last part of the thesis reports, instead, some results in which the properties of clock excitation in bosonic 174Yb have been investigated. By means of high resolution spectroscopic measurements on particles confined in 3D optical lattices, the scattering lengths and loss rate coefficients for atoms in different collisional channels involving the ground level 1S0 and the metastable state 3P0 are derived. These quantities, that at our knowledge were still unreported in literature before our work, set important constraints for future experimental studies of two-electron atoms for quantum-technological applications.

Bose-Einstein condensates (BECs) in light-induced synthetic gauge fields and spaces can provide a highly-tunable platform for quantum simulations. Chapter 1 presents a short introduction to the concepts of BECs and our BEC machine. Chapter 2 introduces some basic ideas of how to use light-matter interactions to create synthetic gauge fields and spaces for neutral atoms. Three main research topics of the thesis are summarized below.

Chapter 3: Recently, using bosonic quasiparticles (including their condensates) as spin carriers in spintronics has become promising for coherent spin transport over macroscopic distances. However, understanding the effects of spin-orbit (SO) coupling and many-body interactions on such a spin transport is barely explored. We study the effects of synthetic SO coupling (which can be turned on and off, not allowed in usual materials) and atomic interactions on the spin transport in an atomic BEC.

Chapter 4: Interplay between matter and fields in physical spaces with nontrivial geometries can lead to phenomena unattainable in planar spaces. However, realizing such spaces is often impeded by experimental challenges. We synthesize real and curved synthetic dimensions into a Hall cylinder for a BEC, which develops symmetry-protected topological states absent in the planar counterpart. Our work opens the door to engineering synthetic gauge fields in spaces with a wide range of geometries and observing novel phenomena inherent to such spaces.

Chapter 5: Rotational properties of a BEC are important to study its superfluidity. Recent studies have found that SO coupling can change a BEC's rotational and superfluid properties, but this topic is barely explored experimentally. We study rotational dynamics of a SO-coupled BEC in an effective rotating frame induced by a synthetic magnetic field. Our work may allow for studying how SO coupling modify a BEC's rotational and superfluid properties.

Chapter 6 presents some possible future directions.