6,680 research outputs found
Occupation of a resonant level coupled to a chiral Luttinger liquid
We consider a resonant level coupled to a chiral Luttinger liquid which can
be realized, e.g., at a fractional quantum Hall edge. We study the dependence
of the occupation probability n of the level on its energy \epsilon for various
values of the Luttinger-liquid parameter g. At g<1/2 a weakly coupled level
shows a sharp jump in n(\epsilon) at the Fermi level. As the coupling is
increased, the magnitude of the jump decreases until \sqrt{2g}, and then the
discontinuity in n(\epsilon) disappears. We show that n(\epsilon) can be
expressed in terms of the magnetization of a Kondo impurity as a function of
magnetic field.Comment: 5 pages including 1 figur
Thermal conductivity of the degenerate one-dimensional Fermi gas
We study heat transport in a gas of one-dimensional fermions in the presence
of a small temperature gradient. At temperatures well below the Fermi energy
there are two types of relaxation processes in this system, with dramatically
different relaxation rates. As a result, in addition to the usual thermal
conductivity, one can introduce the thermal conductivity of the gas of
elementary excitations, which quantifies the dissipation in the system in the
broad range of frequencies between the two relaxation rates. We develop a
microscopic theory of these transport coefficients in the limit of weak
interactions between the fermions.Comment: 17 page
Decay of Bogoliubov excitations in one-dimensional Bose gases
We study the decay of Bogoliubov quasiparticles in one-dimensional Bose
gases. Starting from the hydrodynamic Hamiltonian, we develop a microscopic
theory that enables one to systematically study both the excitations and their
decay. At zero temperature, the leading mechanism of decay of a quasiparticle
is disintegration into three others. We find that low-energy quasiparticles
(phonons) decay with the rate that scales with the seventh power of momentum,
whereas the rate of decay of the high-energy quasiparticles does not depend on
momentum. In addition, our approach allows us to study analytically the
quasiparticle decay in the whole crossover region between the two limiting
cases. When applied to integrable models, including the Lieb-Liniger model of
bosons with contact repulsion, our theory confirms the absence of the decay of
quasiparticle excitations. We account for two types of integrability-breaking
perturbations that enable finite decay: three-body interaction between the
bosons and two-body interaction of finite range.Comment: 17 page
Quantum criticality in a double quantum-dot system
We discuss the realization of the quantum-critical non-Fermi liquid state,
originally discovered within the two-impurity Kondo model, in double
quantum-dot systems. Contrary to the common belief, the corresponding fixed
point is robust against particle-hole and various other asymmetries, and is
only unstable to charge transfer between the two dots. We propose an
experimental set-up where such charge transfer processes are suppressed,
allowing a controlled approach to the quantum critical state. We also discuss
transport and scaling properties in the vicinity of the critical point.Comment: 4 pages, 3 figs; (v2) final version as publishe
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