Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-orbital Kondo effect in quantum dot coupled to ferromagnetic leads   We study the Kondo effect of a two-orbital vertical quantum dot (QD) coupled
to two ferromagnetic leads by employing an equation of motion method. When the
ferromagnetic leads are coupled with parallel spin polarization, we find three
peaks in the single-particle excitation spectra. The middle one is the Kondo
resonance caused by the orbital degrees of freedom. In magnetic fields, the
Kondo effect vanishes. However, at a certain magnetic field new two-fold
degenerate states arise and the Kondo effect emerges there. In contrast, when
the ferromagnetic leads are coupled with antiparallel spin polarization, the
Kondo effect caused by the spin (orbital) degrees of freedom survives (is
suppressed) in magnetic fields. We investigate the field dependence of the
conductance in the parallel and antiparallel spin polarizations of the leads
and find that the conductance changes noticeably in magnetic fields.

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The categories of this paper are: physics
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: nlin
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The categories of this paper are: hep-ph
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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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The categories of this paper are: cs
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con