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Yun-Juan Bao

Bio: Yun-Juan Bao is an academic researcher from University of Hong Kong. The author has contributed to research in topics: Quantum spin Hall effect & Spin Hall effect. The author has an hindex of 4, co-authored 5 publications receiving 77 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, Chen et al. generalized the Dresselhaus coupling to include the Rashba coupling and showed that the spin Hall current is highly nonohmic at low temperatures in two-dimensional quantum wells with spin-orbit interaction under a strong perpendicular magnetic field.
Abstract: A previous work [Shen, Ma, Xie, and Zhang, Phys. Rev. Lett. 92, 256603 (2004)] on two-dimensional quantum wells with Rashba type spin-orbit interaction under a strong perpendicular magnetic field is generalized to include the Dresselhaus coupling. The Rashba coupling and the Dresselhaus coupling interplay with the Zeeman effect in opposing ways. The former tends to produce a resonant spin Hall effect at certain magnetic fields while the latter suppresses it. Due to the resonant spin Hall effect, the spin Hall current is highly nonohmic at low temperatures. The condition for the resonant spin Hall conductance in the presence of both Rashba and Dresselhaus couplings is derived using a perturbation method. In the presence of disorder, we argue that the resonant spin Hall conductance occurs when the two Zeeman split extended states near the Fermi level become degenerate due to the Rashba coupling, and that the quantized charge Hall conductance changes by $2{e}^{2}∕h$ instead of ${e}^{2}∕h$ as the magnetic field changes through the resonant field.

42 citations

Journal ArticleDOI
01 Aug 2008-EPL
TL;DR: In this paper, it was shown that a conductance plateau emerges in the non-linear charge conductance by a spin bias in the Kondo regime, which originates from strong electron correlation and exchange processes in the quantum dot and can be regarded as one of the characteristics in quantum spin transport.
Abstract: Quantum spin transport is studied in an interacting quantum dot. It is found that a conductance "plateau" emerges in the non-linear charge conductance by a spin bias in the Kondo regime. The conductance plateau, as a complementary to the Kondo peak, originates from the strong electron correlation and exchange processes in the quantum dot, and can be regarded as one of the characteristics in quantum spin transport.

19 citations

Journal ArticleDOI
TL;DR: In this paper, the electric response of spin polarization in two-dimensional electron gas with structural inversion asymmetry subjected to a magnetic field was studied by means of the linear and non-linear theory and numerical simulation with the disorder effect.
Abstract: Electric response of spin polarization in two-dimensional electron gas with structural inversion asymmetry subjected to a magnetic field was studied by means of the linear and non-linear theory and numerical simulation with the disorder effect. It was found by Kubo linear reponse theory that an electric resonant response of spin polarization occurs when the Fermi surface is located near the crossing of two Landau levels, which is induced from the competition between the spin-orbit coupling and Zeeman splitting. The scaling behavior was investigated with a simplified two-level model by non-linear method, and the resonant peak value is reciprocally proportional to the electric field at low temperatures and to temperature for finite electric fields. Finally numerical simulation illustrated that impurity potential opens an enegy gap near the resonant point and suppresses the effect gradually with the increasing strength of disorder. This resonant effect may provide an efficient way to control spin polarization by an external electric field.

11 citations

Journal ArticleDOI
TL;DR: In this article, the edge spin current and spin polarization in a two-dimensional electron gas with spin-orbit coupling in the presence of a perpendicular magnetic field were studied. And the edge effect removed the degeneracy of Landau levels due to the competition between the Rashba coupling and the Zeeman splitting, which exists in the bulk.
Abstract: We study the edge spin current and spin polarization in a two-dimensional electron gas with spin-orbit coupling in the presence of a perpendicular magnetic field. The edge effect removes the degeneracy of Landau levels due to the competition between the Rashba coupling and the Zeeman splitting, which exists in the bulk. Large spin edge current and non-linear response to an electric field are found when the two levels are degenerated in the bulk. It is found that he spin current is proportional to spin polarization along the y-direction in an finite magnetic field, which provides a way to extract the spin current in the system.

8 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that a conductance plateau emerges in the non-linear charge conductance by a spin bias in the Kondo regime, which originates from strong electron correlation and exchange processes in the quantum dot and can be regarded as one of the characteristics in quantum spin transport.
Abstract: Quantum spin transport is studied in an interacting quantum dot. It is found that a conductance "plateau" emerges in the non-linear charge conductance by a spin bias in the Kondo regime. The conductance plateau, as a complementary to the Kondo peak, originates from the strong electron correlation and exchange processes in the quantum dot, and can be regarded as one of the characteristics in quantum spin transport.

1 citations


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Journal Article
TL;DR: The study on general process and methods for scientific knowledge proves that science, which is based on experience and beyoud experience, is a way and method to verify experience.
Abstract: Science is an effective way for man to know the world.With individual objects as direct research objects,and general existing state of the objects as targets,with the help of scientific suppositions their verification and other methods to surpass gap among experience and superexperience targets,it obtains the knowledge of the objects.The study on general process and methods for scientific knowledge proves that science,which is based on experience and beyoud experience,is a way and method to verify experience.

410 citations

Journal ArticleDOI
TL;DR: In this article, a fitting formula for the magnetoconductivity of weak anti-localization was proposed for topological semimetals and the dependence of the negative magnetoresistance on the carrier density was shown.
Abstract: Topological semimetals are three-dimensional topological states of matter, in which the conduction and valence bands touch at a finite number of points, i.e., the Weyl nodes. Topological semimetals host paired monopoles and antimonopoles of Berry curvature at the Weyl nodes and topologically protected Fermi arcs at certain surfaces. We review our recent works on quantum transport in topological semimetals, according to the strength of the magnetic field. At weak magnetic fields, there are competitions between the positive magnetoresistivity induced by the weak anti-localization effect and negative magnetoresistivity related to the nontrivial Berry curvature. We propose a fitting formula for the magnetoconductivity of the weak anti-localization. We expect that the weak localization may be induced by inter-valley effects and interaction effect, and occur in double-Weyl semimetals. For the negative magnetoresistance induced by the nontrivial Berry curvature in topological semimetals, we show the dependence of the negative magnetoresistance on the carrier density. At strong magnetic fields, specifically, in the quantum limit, the magnetoconductivity depends on the type and range of the scattering potential of disorder. The high-field positive magnetoconductivity may not be a compelling signature of the chiral anomaly. For long-range Gaussian scattering potential and half filling, the magnetoconductivity can be linear in the quantum limit. A minimal conductivity is found at the Weyl nodes although the density of states vanishes there.

136 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that the angular spin current (or spin torque) can also induce an electric field, similar to the linear spin current, and the formula for the induced electric field was derived, playing the role of ''Biot-Savart law'' or ''Ampere law''.
Abstract: We find that in order to completely describe the spin transport, apart from spin current (or linear spin current), one has to introduce the angular spin current. The two spin currents, respectively, describe the translational and rotational motion (precession) of a spin. The definitions of these spin current densities are given and their physical properties are discussed. Both spin current densities appear naturally in the spin continuity equation. In particular, we predict that the angular spin current (or the spin torque as called in previous works), similar to the linear spin current, can also induce an electric field $\stackrel{P\vec}{E}$. The formula for the induced electric field $\stackrel{P\vec}{E}$ by the angular spin current element is derived, playing the role of ``Biot-Savart law'' or ``Ampere law.'' When at large distance $r$, this induced electric field $\stackrel{P\vec}{E}$ scales as $1∕{r}^{2}$, whereas the $\stackrel{P\vec}{E}$ field generated from the linear spin current goes as $1∕{r}^{3}$.

133 citations

Journal ArticleDOI
TL;DR: A review of physical processes related to disorder in spin-orbit coupling in two-dimensional electron gas is presented in this article, where spin relaxation of free and localized electrons, memory effects and spin relaxation enhancement in magnetic field, and spin manipulation and spin current injection by external electric fields in the structures where the spinorbit coupling is random, are considered.
Abstract: A review of physical processes related to disorder in spin–orbit coupling in two-dimensional electron gas is presented. We begin with the analysis of the sources of the randomness in the spin–orbit coupling in semiconductor structures and establish the corresponding Hamiltonian. We demonstrate that in multiple quantum wells electron–electron interaction is a source of a time-dependent randomness in the spin–orbit coupling, additional to that provided by the static disorder. The spin relaxation of free and localized in quantum dots electrons, memory effects and spin relaxation enhancement in magnetic field, and spin manipulation and spin current injection by external electric fields in the structures where the spin–orbit coupling is random, are considered. In addition, we study spin relaxation in single-layer graphene, which provides an excellent example of a system with disordered spin–orbit coupling.

81 citations

Journal ArticleDOI
TL;DR: The intrinsic spin Hall effect in semiconductors has developed to a remarkably lively and rapidly growing branch of research in the field of semiconductor spintronics as mentioned in this paper, and a pedagogical overview on both theoretical and experimental accomplishments and challenges.
Abstract: The intrinsic spin Hall effect in semiconductors has developed to a remarkably lively and rapidly growing branch of research in the field of semiconductor spintronics. In this article we give a pedagogical overview on both theoretical and experimental accomplishments and challenges. Emphasis is put on the the description of the intrinsic mechanisms of spin Hall transport in III-V zinc-blende semiconductors and on the effects of dissipation.

71 citations