338 research outputs found
Spin-orbit coupling effects in one-dimensional ballistic quantum wires
We study the spin-dependent electronic transport through a one-dimensional
ballistic quantum wire in the presence of Rashba spin-orbit interaction. In
particular, we consider the effect of the spin-orbit interaction resulting from
the lateral confinement of the two-dimensional electron gas to the
one-dimensional wire geometry. We generalize a situation suggested earlier [P.
Streda and P. Seba, Phys. Rev. Lett. 90, 256601 (2003)] which allows for
spin-polarized electron transport. As a result of the lateral confinement, the
spin is rotated out of the plane of the two-dimensional system. We furthermore
investigate the spin-dependent transmission and the polarization of an electron
current at a potential barrier. Finally, we construct a lattice model which
shows similar low-energy physics. In the future, this lattice model will allow
us to study how the electron-electron interaction affects the transport
properties of the present setup.Comment: 7 pages, 6 figures, revised versio
Improved transport equations including correlations for electron-phonon systems. Comparison with exact solutions in one dimension
We study transport equations for quantum many-particle systems in terms of
correlations by applying the general formalism developed in an earlier paper to
exactly soluble electron-phonon models. The one-dimensional models considered
are the polaron model with a linear energy dispersion for the electrons and a
finite number of electrons and the same model including a Fermi sea
(Tomonaga-Luttinger model). The inclusion of two-particle correlations shows a
significant and systematic improvement in comparison with the usual
non-Markovian equations in Born approximation. For example, the improved
equations take into account the renormalization of the propagation by the
self-energies to second order in the coupling.Comment: 20 pages, 15 Postscript figures, uses RevTeX, to be published in:
Annals of Physics (N.Y.
Luttinger liquid universality in the time evolution after an interaction quench
We provide strong evidence that the relaxation dynamics of one-dimensional,
metallic Fermi systems resulting out of an abrupt amplitude change of the
two-particle interaction has aspects which are universal in the Luttinger
liquid sense: The leading long-time behavior of certain observables is
described by universal functions of the equilibrium Luttinger liquid parameter
and the renormalized velocity. We analytically derive those functions for the
Tomonaga-Luttinger model and verify our hypothesis of universality by
considering spinless lattice fermions within the framework of the density
matrix renormalization group
RG transport theory for open quantum systems: Charge fluctuations in multilevel quantum dots in and out of equilibrium
We present the real-time renormalization group (RTRG) method as a method to
describe the stationary state current through generic multi-level quantum dots
with a complex setup in nonequilibrium. The employed approach consists of a
very rudiment approximation for the RG equations which neglects all vertex
corrections while it provides a means to compute the effective dot Liouvillian
self-consistently. Being based on a weak-coupling expansion in the tunneling
between dot and reservoirs, the RTRG approach turns out to reliably describe
charge fluctuations in and out of equilibrium for arbitrary coupling strength,
even at zero temperature. We confirm this in the linear response regime with a
benchmark against highly-accurate numerically renormalization group data in the
exemplary case of three-level quantum dots. For small to intermediate bias
voltages and weak Coulomb interactions, we find an excellent agreement between
RTRG and functional renormalization group data, which can be expected to be
accurate in this regime. As a consequence, we advertise the presented RTRG
approach as an efficient and versatile tool to describe charge fluctuations
theoretically in quantum dot systems
Renormalization group flows in one-dimensional lattice models: impurity scaling, umklapp scattering and the orthogonality catastrophe
We show that to understand the orthogonality catastrophe in the half-filled
lattice model of spinless fermions with repulsive nearest neighbor interaction
and a local impurity in its Luttinger liquid phase one has to take into account
(i) the impurity scaling, (ii) unusual finite size corrections of the form
, as well as (iii) the renormalization group flow of the umklapp
scattering. The latter defines a length scale which becomes exceedingly
large the closer the system is to its transition into the charge-density wave
phase. Beyond this transition umklapp scattering is relevant in the
renormalization group sense. Field theory can only be employed for length
scales larger than . For small to intermediate two-particle interactions,
for which the regime can be accessed, and taking into account the
finite size corrections resulting from (i) and (ii) we provide strong evidence
that the impurity backscattering contribution to the orthogonality exponent is
asymptotically given by . While further increasing the two-particle
interaction leads to a faster renormalization group flow of the impurity
towards the cut chain fixed point, the increased bare amplitude of the umklapp
scattering renders it virtually impossible to confirm the expected asymptotic
value of given the accessible system sizes. We employ the density matrix
renormalization group.Comment: 12 pages, 9 figure
Spectral sum rules for the Tomonaga-Luttinger model
In connection with recent publications we discuss spectral sum rules for the
Tomonaga-Luttinger model without using the explicit result for the one-electron
Green's function. They are usefull in the interpretation of recent high
resolution photoemission spectra of quasi-one-dimensional conductors. It is
shown that the limit of infinite frequency and band cut\-off do not commute.
Our result for arbitrary shape of the interaction potential generalizes an
earlier discussion by Suzumura. A general analytical expression for the
spectral function for wave vectors far from the Fermi wave vector is
presented. Numerical spectra are shown to illustrate the sum rules.Comment: 9 pages, REVTEX 3.0, 2 figures added as postscript file
Spin-polarized currents through interacting quantum wires with nonmagnetic leads
We study the performance of a quantum wire spin filter that is based on the
Rashba spin-orbit interaction in the presence of the electron-electron
interaction. The finite length wire is attached to two semi-infinite
nonmagnetic leads. Analyzing the spin polarization of the linear conductance at
zero temperature, we show that spin-filtering is possible by adequate tuning of
the system parameters first considering noninteracting electrons. Next, the
functional renormalization group method is used to capture correlation effects
induced by the Coulomb interaction. For short wires we show that the energy
regime in which spin polarization is found is strongly affected by the Coulomb
interaction. For long wires we find the power-law suppression of the total
conductance on low energy scales typical for inhomogeneous Luttinger liquids
while the degree of spin polarization stays constant
Understanding the Josephson current through a Kondo-correlated quantum dot
We study the Josephson current 0- transition of a quantum dot tuned to
the Kondo regime. The physics can be quantitatively captured by the numerically
exact continuous time quantum Monte Carlo method applied to the single-impurity
Anderson model with BCS superconducting leads. For a comparison to an
experiment the tunnel couplings are determined by fitting the normal-state
linear conductance. Excellent agreement for the dependence of the critical
Josephson current on the level energy is achieved. For increased tunnel
couplings the Kondo scale becomes comparable to the superconducting gap and the
regime of the strongest competition between superconductivity and Kondo
correlations is reached; we predict the gate voltage dependence of the critical
current in this regime.Comment: 5 pages, 3 figure
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