121 research outputs found
Periodic orbit theory including spin degrees of freedom
We summarize recent developments of the semiclassical description of shell
effects in finite fermion systems with explicit inclusion of spin degrees of
freedom, in particluar in the presence of spin-orbit interactions. We present a
new approach that makes use of spin coherent states and a correspondingly
enlarged classical phase space. Taking suitable limits, we can recover some of
the earlier approaches. Applications to some model systems are presented.Comment: LaTeX2e, 10pp, 5 figs; contribution to 10th Nuclear Physics Workshop
"Marie and Pierre Curie", 24 - 28 Sept. 2003, Kazimierz Dolny (Poland
On the extra phase correction to the semiclassical spin coherent-state propagator
The problem of an origin of the Solary-Kochetov extra-phase contribution to
the naive semiclassical form of a generalized phase-space propagator is
addressed with the special reference to the su(2) spin case which is the most
important in applications. While the extra-phase correction to a flat
phase-space propagator can straightforwardly be shown to appear as a difference
between the principal and the Weyl symbols of a Hamiltonian in the
next-to-leading order expansion in the semiclassical parameter, the same
statement for the semiclassical spin coherent-state propagator holds provided
the Holstein-Primakoff representation of the su(2) algebra generators is
employed.Comment: 19 pages, no figures; a more general treatment is presented, some
references are added, title is slightly changed; submitted to JM
Magnetic field effects on the finite-frequency noise and ac conductance of a Kondo quantum dot out of equilibrium
We present analytic results for the finite-frequency current noise and the
nonequilibrium ac conductance for a Kondo quantum dot in presence of a magnetic
field. Using the real-time renormalization group method, we determine the line
shape close to resonances and show that while all resonances in the ac
conductance are broadened by the transverse spin relaxation rate, the noise at
finite field additionally involves the longitudinal rate as well as sharp kinks
resulting in singular derivatives. Our results provide a consistent theoretical
description of recent experimental data for the emission noise at zero magnetic
field, and we propose the extension to finite field for which we present a
detailed prediction.Comment: 21 pages, 13 figure
Oscillatory dynamics and non-markovian memory in dissipative quantum systems
The nonequilibrium dynamics of a small quantum system coupled to a
dissipative environment is studied. We show that (1) the oscillatory dynamics
close to a coherent-to-incoherent transition is surprisingly different from the
one of the classical damped harmonic oscillator and that (2) non-markovian
memory plays a prominent role in the time evolution after a quantum quench.Comment: 5 pages, 3 figure
Spin-density induced by electromagnetic wave in two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit couplings
We consider the magnetic response of a two-dimensional electron gas (2DEG)
with both Rashba and Dresselhaus spin-orbit coupling to a microwave excitation.
We generalize the results of [A. Shnirman and I. Martin, Europhys. Lett. 78,
27001 (2007).], where pure Rashba coupling was studied. We observe that the
microwave with the in-plane electric field and the out-of-plane magnetic field
creates an out-of-plane spin polarization. The effect is more prominent in
clean systems with resolved spin-orbit-split subbands. Considered as response
to the microwave magnetic field, the spin-orbit contribution to the
magnetization far exceeds the usual Zeeman contribution in the clean limit. The
effect vanishes when the Rashba and the Dresselhaus couplings have equal
strength.Comment: 4 pages, 2 figure
Charge and spin density response functions of the clean two-dimensional electron gas with Rashba spin-orbit coupling at finite momenta and frequencies
We analytically evaluate charge and spin density response functions of the
clean two-dimensional electron gas with Rashba spin-orbit coupling at finite
momenta and frequencies. On the basis of our exact expressions we discuss the
accuracy of the long-wavelength and the quasiclassical approximations. We also
derive the static limit of spin susceptibilities and demonstrate, in
particular, how the Kohn-like anomalies in their derivatives are related to the
spin-orbit modification of the Ruderman-Kittel-Kasuya-Yosida interaction.
Taking into account screening and exchange effects of the Coulomb interaction,
we describe the collective charge and spin density excitation modes which
appear to be coupled due to nonvanishing spin-charge response function.Comment: 15 pages, 9 figure
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