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Featured researches published by K. Shen.


Physical Review B | 2008

Robust strongly modulated transmission of a T-shaped structure with local Rashba interaction

K. Shen; M. W. Wu

(Dated: April 16, 2008)We propose a scheme of spin transistor using a T-shaped structure with local Rashba interaction.A wide antiresonance energy gap appears due to the interplay of two types of interference, theFano-Rashba interference and the structure interference. A large current from the gap area can beobtained via changing the Rashba strength and/or the length of the sidearm by using gate voltage.The robustness of the antiresonance gap against strong disorder is demonstrated and shows thefeasibility of this structure for the real application.


Physical Review B | 2010

Singlet-triplet relaxation in multivalley silicon single quantum dots

Liu-Jun Wang; K. Shen; B. Y. Sun; M. W. Wu

We investigate the singlet-triplet relaxation due to the spin-orbit coupling together with the electron-phonon scattering in two-electron multivalley silicon single quantum dots, using the exact-diagonalization method and the Fermi golden rule. The electron-electron Coulomb interaction, which is crucial in the electronic structure is explicitly included. The multivalley effect induced by the interface scattering is also taken into account. We first study the configuration with a magnetic field in the Voigt configuration and identify the relaxation channel of the experimental data by Xiao et al. [Phys. Rev. Lett. 104, 096801 (2010)]. Good agreement with the experiment is obtained. Moreover, we predict a peak in the magnetic-field dependence of the singlet-triplet relaxation rate induced by the anticrossing of the singlet and triplet states. We then work on the system with a magnetic field in the Faraday configuration, where the different values of the valley splitting are discussed. In the case of large valley splitting, we find the transition rates can be effectively manipulated by varying the external magnetic field and the dot size. The intriguing features of the singlet-triplet relaxation in the vicinity of the anticrossing point are analyzed. In the case of small valley splitting, we find that the transition rates are much smaller than those in the case of large valley splitting, resulting from the different configurations of the triplet states.


Journal of Applied Physics | 2008

A scheme for spin transistor with extremely large on/off current ratio

Liu-Jun Wang; K. Shen; S. Y. Cho; M. W. Wu

Quantum wires with periodic local Rashba spin-orbit couplings are proposed for a higher performance of spin field-effect transistor. Fano–Rashba quantum interference due to the spin-dependent modulated structure gives rise to a broad energy range of vanishingly small transmission. Tuning Rashba spin-orbit couplings can provide the on or off currents with extremely large on/off current ratios even in the presence of a strong disorder.


Journal of Applied Physics | 2008

L-valley electron g-factor in bulk GaAs and AlAs

K. Shen; M. Q. Weng; M. W. Wu

We study the Lande g-factor of conduction electrons in the L-valley of bulk GaAs and AlAs by using a three-band k⋅p model together with the tight-binding model. We find that the L-valley g-factor is highly anisotropic and can be characterized by two components g⊥ and g∥. g⊥ is close to the free electron Lande factor but g∥ is strongly affected by the remote bands. The contribution from remote bands on g∥ depends on how the remote bands are treated. However, when the magnetic field is in the Voigt configuration, which is widely used in the experiments, different models give almost identical g-factor.


Physical Review B | 2007

Triplet-singlet relaxation in semiconductor single and double quantum dots

K. Shen; M. W. Wu

We study the triplet-singlet relaxation in two-electron semiconductor quantum dots. Both single dots and vertically coupled double dots are discussed. In our work, the electron-electron Coulomb interaction, which plays an important role in the electronic structure, is included. The spin mixing is caused by spin-orbit coupling which is the key to the triplet-singlet relaxation. We show that the selection rule widely used in the literature is incorrect unless near the crossing and/or anticrossing point in single quantum dots. The triplet-singlet relaxation in double quantum dots can be markedly changed by varying barrier height, interdot distance, external magnetic field, and dot size.


Physical Review B | 2011

Existence of vertical spin stiffness in Landau-Lifshitz-Gilbert equation in ferromagnetic semiconductors

K. Shen; Gen Tatara; M. W. Wu

We calculate the magnetization torque due to the spin polarization of the itinerant electrons by deriving the kinetic spin Bloch equations based on the


Physical Review B | 2010

Effect of spin-conserving scattering on Gilbert damping in ferromagnetic semiconductors

K. Shen; Gen Tatara; M. W. Wu

s


Solid State Communications | 2011

Spin diffusion in n-type (111) GaAs quantum wells

B. Y. Sun; K. Shen

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Physical Review B | 2010

Hole spin relaxation in intrinsic and p-type bulk GaAs

K. Shen; M. W. Wu

d


Solid State Communications | 2011

Spin–orbit coupling and g-factor of X-valley in cubic GaN

K. Shen; J.Y. Fu; M. W. Wu

model. We find that the first-order gradient of the magnetization inhomogeneity gives rise to the current-induced torques, which are consistent to the previous works. At the second-order gradient, we find an effective magnetic field perpendicular to the spin stiffness filed. This field is proportional to the nonadiabatic parameter

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M. W. Wu

University of Science and Technology of China

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J.Y. Fu

Qufu Normal University

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B. Y. Sun

University of Science and Technology of China

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Liu-Jun Wang

University of Science and Technology of China

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Mingzai Wu

University of Science and Technology of China

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Gen Tatara

Tokyo Metropolitan University

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M. Q. Weng

University of Science and Technology of China

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