Spin-Dependent Ringing and Beats in a Quantum Dot System

Abstract

We report spin-dependent quantum coherent oscillations (ringing) and beats of the total and spin currents flowing through a quantum dot with Zeeman split levels. The spin dependent transport is calculated via nonequilibrium Green function in the transient after a bias voltage is turned on at t=0. The dot is coupled to two electrodes that can be ferromagnetic or nonmagnetic. In the ferromagnetic case both parallel and antiparallel alignments are considered. The coherent oscillation and beat frequencies are controlled via the Zeeman energy E_Z. In particular, for E_Z=0 no beats are observed and the spin current is zero for nonmagnetic leads. In the ferromagnetic case a finite spin current is found for E_Z=0. The effects of temperature are also analyzed. We observe that with increasing temperature the ringing response and the beats tend to disappear. Additionally, the spin current goes to zero for nonmagnetic leads, remaining finite in the ferromagnetic case. The tunnel magnetoresistance (TMR) also reveals quantum coherent oscillations and beats, and it attains negative values for small enough temperatures and short times.

published version: reference added, typos corrected, minor changes in the text

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• Correlation induced memory effects in the transport properties of low dimensional systems
• Ultrafast manipulation of electron spins in a double quantum dot device: A real-time view
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• Time-dependent Andreev bound states of a quantum dot coupled to two superconducting leads
• Transient probing of the symmetry and the asymmetry of electron interference
• Time-Dependent Thermopower Effect in an Interacting Quantum Dot
• Enhanced photon-assisted spin transport in a quantum dot attached to ferromagnetic leads
• Lindblad Formalism based on Fermion-to-Qubit mapping for Non-equilibrium Open-Quantum Systems
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• Dimensionality effects in the LDOS of ferromagnetic hosts probed via STM: spin-polarized quantum beats and spin filtering
• Charge waves and dynamical signatures of topological phases in Su-Schrieffer-Heeger chains