C. S. Chu

Spin-current generation and detection in the presence of an ac gate

We predict that in a narrow gap III-V semiconductor quantum well or quantum wire, an observable electron spin current can be generated with a time-dependent gate to modify the Rashba spin-orbit coupling constant. Methods to rectify the so generated ac current are discussed. An all-electric method of spin-current detection is suggested, which measures the voltage on the gate in the vicinity of a two-dimensional electron gas carrying a time-dependent spin current. Both the generation and detection do not involve any optical or magnetic mediator.

Connecting wave functions at a three-leg junction of one-dimensional channels

We propose a scheme to connect the wave functions on different one-dimensional branches of a three-leg junction (

Coherent quantum transport in narrow constrictions in the presence of a finite-range longitudinally polarized time-dependent field

Y

Strain-Induced Coupling of Spin Current to Nanomechanical Oscillations

junction). Our scheme differs from that due to Griffith [Trans. Faraday Soc. 49, 345 (1953)] in the respect that ours can model the difference in the widths of the quasi-one-dimensional channels in different systems. We test our scheme by comparing results from a doubly connected one-dimensional system and a related quasi-one-dimensional system, and we find a good agreement. Therefore our scheme may be useful in the construction of one-dimensional effective models out of (multiply connected) quasi-one-dimensional systems.

QUANTUM TRANSPORT IN THE PRESENCE OF A FINITE-RANGE TIME-MODULATED POTENTIAL

We have studied the quantum transport in a narrow constriction acted upon by a finite-range longitudinally polarized time-dependent electric field. The electric field induces coherent inelastic scatterings that involve both intrasubband and intersideband transitions. Subsequently, the dc conductance G is found to exhibit suppressed features. These features are recognized as the quasi-bound-state (QBS) features that are associated with electrons making transitions to the vicinity of a subband bottom, of which the density of states is singular. Having valleylike instead of diplike structures, these QBS features are different from the G characteristics for constrictions acted upon by a finite-range time-modulated potential. In addition, the subband bottoms in the time-dependent electric-field region are shifted upward by an energy proportional to the square of the electric field and inversely proportional to the square of the frequency. This effective potential barrier is originated from the square of the vector potential, and it leads to the interesting field-sensitive QBS features. An experimental setup is proposed for the observation of these features.

Localized states in continuum in low-dimensional systems

We propose a setup which allows us to couple the electron spin degree of freedom to the mechanical motions of a nanomechanical system not involving any of the ferromagnetic components. The proposed method employs the strain-induced spin-orbit interaction of electrons in narrow gap semiconductors. We have shown how this method can be used for detection and manipulation of the spin flow through a suspended rod in a nanomechanical device.

Transport spectroscopy in a time-modulated open quantum dot

Quantum transport in a narrow constriction, and in the presence of a finite-range time-modulated potential, is studied. The potential is taken the form

dc spin current generation in a Rashba-type quantum channel

V(x,t) = V_{0} \theta(x)\theta(a-x)\cos(\omega t)

Spin-Hall interface resistance in terms of Landauer-type spin dipoles

, with

Spin orientation and spin-Hall effect induced by tunneling electrons

a