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Hubbard ladders in a magnetic field
The behavior of a two leg Hubbard ladder in the presence of a magnetic field is studied by means of Abelian bosonization. We predict the appearance of a new (doping dependent) plateau in the magnetization curve of a doped 2-leg spin ladder in a wide range of couplings. We also discuss the extension to N-leg Hubbard ladders
Resonant tunnelling between Luttinger liquids: solvable case
We discuss the conductance of a Luttinger liquid interrupted by a quantum dot
containing a single resonant level. Using bosonisation and re-fermionisation
methods, we find a mapping to a Kondo-type problem which possesses a
non-trivial Toulouse-type solvable point. At this point, we obtain an analytic
expression for the non-linear current-voltage characteristics and analyse the
differential conductance and the width of the resonance peak as functions of
bias and gate voltages, temperature, and barrier asymmetry. We also determine
the exact scaling function for the linear conductance.Comment: 4 pages, 3 figures (eps files
Current facilitation by plasmon resonances between parallel wires of finite length
The current voltage (IV) characteristics for perpendicular transport through
two sequentially coupled wires of finite length is calculated analytically. The
transport within a Coulomb blockade step is assisted by plasmon resonances that
appear as steps in the IV characteristics with positions and heights depending
on inter- and intrawire interactions. In particular, due to the interwire
interactions, the peak positions shift to lower voltages in comparison to the
noninteracting wires which reflects the facilitation of current by
interactions. The interwire interactions are also found to enhance the
thermally activated current.Comment: 5 pages, 1figur
Preferred Basis in a Measurement Process
The effect of decoherence is analysed for a free particle, interacting with
an environment via a dissipative coupling. The interaction between the particle
and the environment occurs by a coupling of the position operator of the
particle with the environmental degrees of freedom. By examining the exact
solution of the density matrix equation one finds that the density matrix
becomes completely diagonal in momentum with time while the position space
density matrix remains nonlocal. This establishes the momentum basis as the
emergent 'preferred basis' selected by the environment which is contrary to the
general expectation that position should emerge as the preferred basis since
the coupling with the environment is via the position coordinate.Comment: Standard REVTeX format, 10 pages of output. Accepted for publication
in Phys. Rev
Models for local ohmic quantum dissipation
We construct model master equations for local quantum dissipation. The master
equations are in the form of Lindblad generators, with imposed constraints that
the dissipations be strictly linear (i.e. ohmic), isotropic and translationally
invariant. A particular form for is chosen to satisfy the constraints. The
resulting master equations are given in both the Schr\"odinger and Heisenberg
forms. We obtain fluctuation-dissipation relations, and discuss the relaxation
of average kinetic energy to effective thermal equilibrium values. We compare
our results to the Dekker and the Caldeira-Leggett master equations. These
master equations allow a more general approach to quantum dissipation and the
dynamics of quantum coherence to account for the nontrivial system-environment
coupling in a local environment.Comment: 19 pages, REVTEX, PSU/TH/12
Resistivity due to low-symmetrical defects in metals
The impurity resistivity, also known as the residual resistivity, is
calculated ab initio using multiple-scattering theory. The mean-free path is
calculated by solving the Boltzmann equation iteratively. The resistivity due
to low-symmetrical defects, such as an impurity-vacancy pair, is calculated for
the FCC host metals Al and Ag and the BCC transition metal V. Commonly, 1/f
noise is attributed to the motion of such defects in a diffusion process.Comment: 24 pages in REVTEX-preprint format, 10 Postscript figures. Phys. Rev.
B, vol. 57 (1998), accepted for publicatio
Bulk and boundary zero-bias anomaly in multi-wall carbon nanotubes
We compute the tunneling density of states of doped multi-wall nanotubes
including disorder and electron-electron interactions. A non-conventional
Coulomb blockade reflecting nonperturbative Altshuler-Aronov-Lee power-law
zero-bias anomalies is found, in accordance with recent experimental results.
The presence of a boundary implies a universal doubling of the boundary
exponent in the diffusive limit.Comment: 4 pages, to appear in PRL (revised version
Spin-orbit coupling and electron spin resonance for interacting electrons in carbon nanotubes
We review the theoretical description of spin-orbit scattering and electron
spin resonance in carbon nanotubes. Particular emphasis is laid on the effects
of electron-electron interactions. The spin-orbit coupling is derived, and the
resulting ESR spectrum is analyzed both using the effective low-energy field
theory and numerical studies of finite-size Hubbard chains and two-leg Hubbard
ladders. For single-wall tubes, the field theoretical description predicts a
double peak spectrum linked to the existence of spin-charge separation. The
numerical analysis basically confirms this picture, but also predicts
additional features in finite-size samples.Comment: 19 pages, 4 figures, invited review article for special issue in J.
Phys. Cond. Mat., published versio
Competition between magnetic field dependent band structure and coherent backscattering in multiwall carbon nanotubes
Magnetotransport measurements in large diameter multiwall carbon nanotubes
(20-40 nm) demonstrate the competition of a magnetic-field dependent
bandstructure and Altshuler-Aronov-Spivak oscillations. By means of an
efficient capacitive coupling to a backgate electrode, the magnetoconductance
oscillations are explored as a function of Fermi level shift. Changing the
magnetic field orientation with respect to the tube axis and by ensemble
averaging, allows to identify the contributions of different Aharonov-Bohm
phases. The results are in qualitative agreement with numerical calculations of
the band structure and the conductance.Comment: 4 figures, 5 page
Current fluctuations in a single tunnel junction
We study noise spectra of currents through a tunnel junction in weak
tunneling limit. We introduce effective capacitance to take into account the
interaction effect and explicitly incorporate the electromagnetic environment
of the junction into the formulation. We study the effect of charging energy
and macroscopic environment on noise spectra. We calculate current fluctuations
at tunneling barrier and fluctuations measured at leads. It is shown that two
fluctuations have different noise spectra and the relation between them is
nontrivial. We provide an explanation for the origin of the difference.
Experimental implications are discussed.Comment: 25 pages, Revtex 3.
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