8,185 research outputs found
Voltage-biased quantum wire with impurities
The bosonization technique to describe correlated electrons in a
one-dimensional quantum wire containing impurities is extended to include an
applied voltage source. The external reservoirs are shown to lead to a boundary
condition for the boson phase fields. We use the formalism to investigate the
channel conductance, electroneutrality, and charging effects.Comment: 4 pages REVTeX, incl one figure, to appear in Phys.Rev.Let
On the effects of irrelevant boundary scaling operators
We investigate consequences of adding irrelevant (or less relevant) boundary
operators to a (1+1)-dimensional field theory, using the Ising and the boundary
sine-Gordon model as examples. In the integrable case, irrelevant perturbations
are shown to multiply reflection matrices by CDD factors: the low-energy
behavior is not changed, while various high-energy behaviors are possible,
including ``roaming'' RG trajectories. In the non-integrable case, a Monte
Carlo study shows that the IR behavior is again generically unchanged, provided
scaling variables are appropriately renormalized.Comment: 4 Pages RevTeX, 3 figures (eps files
Doping- and size-dependent suppression of tunneling in carbon nanotubes
We study the effect of doping in the suppression of tunneling observed in
multi-walled nanotubes, incorporating as well the influence of the finite
dimensions of the system. A scaling approach allows us to encompass the
different values of the critical exponent measured for the tunneling
density of states in carbon nanotubes. We predict that further reduction of
should be observed in multi-walled nanotubes with a sizeable amount
of doping. In the case of nanotubes with a very large radius, we find a
pronounced crossover between a high-energy regime with persistent
quasiparticles and a low-energy regime with the properties of a one-dimensional
conductor.Comment: 4 pages, 2 figures, LaTeX file, pacs: 71.10.Pm, 71.20.Tx, 72.80.R
Resonant tunneling in a Luttinger liquid for arbitrary barrier transmission
A numerically exact dynamical quantum Monte Carlo approach has been developed
and applied to transport through a double barrier in a Luttinger liquid with
arbitrary transmission. For strong transmission, we find broad Fabry-Perot
Coulomb blockade peaks, with a lineshape parametrized by a single parameter,
but at sufficiently low temperatures, non-Lorentzian universal lineshapes
characteristic of coherent resonant tunneling emerge, even for strong
interactions. For weak transmission, our data supports the recently proposed
correlated sequential tunneling picture and is consistent with experimental
results on intrinsic nanotube dots.Comment: 4 pages, 4 figure
Transport in Double-Crossed Luttinger Liquids
We study transport through two Luttinger liquids (one-dimensional electrons
interacting through a Coulomb repulsion in a metal) coupled together at {\it
two} points. External voltage biases are incorporated through boundary
conditions. We include density-density couplings as well as single-particle
hops at the contacts. For weak repulsive interactions, transport through the
wires remains undisturbed by the inter-wire couplings, which renormalise to
zero. For strong repulsive interactions, the inter-wire couplings become
strong. For symmetric barriers and no external voltage bias, a single gate
voltage is sufficient to tune for resonance transmission in both wires.
However, for asymmetric couplings or for finite external biases, the system is
insulating.Comment: Latex file, 11 pages, one eps figur
Luttinger liquid behavior in multi-wall carbon nanotubes
The low-energy theory for multi-wall carbon nanotubes including the
long-ranged Coulomb interactions, internal screening effects, and
single-electron hopping between graphite shells is derived and analyzed by
bosonization methods. Characteristic Luttinger liquid power laws are found for
the tunneling density of states, with exponents approaching their Fermi liquid
value only very slowly as the number of conducting shells increases. With minor
modifications, the same conclusions apply to transport in ropes of single-wall
nanotubes.Comment: 4 pages Revte
Towards realistic implementations of a Majorana surface code
Surface codes have emerged as promising candidates for quantum information
processing. Building on the previous idea to realize the physical qubits of
such systems in terms of Majorana bound states supported by topological
semiconductor nanowires, we show that the basic code operations, namely
projective stabilizer measurements and qubit manipulations, can be implemented
by conventional tunnel conductance probes and charge pumping via
single-electron transistors, respectively. The simplicity of the access scheme
suggests that a functional code might be in close experimental reach.Comment: 5 pages, 1 p. suppl.mat, PRL in pres
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