Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin-Dependent Ringing and Beats in a Quantum Dot System   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.

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The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: econ
2
The categories of this paper are: math
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: astro-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con