142 research outputs found
Brownian scattering of a spinon in a Luttinger liquid
We consider strongly interacting one-dimensional electron liquids where
elementary excitations carry either spin or charge. At small temperatures a
spinon created at the bottom of its band scatters off low-energy spin- and
charge-excitations and follows the diffusive motion of a Brownian particle in
momentum space. We calculate the mobility characterizing these processes, and
show that the resulting diffusion coefficient of the spinon is parametrically
enhanced at low temperatures compared to that of a mobile impurity in a
spinless Luttinger liquid. We briefly discuss that this hints at the relevance
of spin in the process of equilibration of strongly interacting one-dimensional
electrons, and comment on implications for transport in clean single channel
quantum wires
Strong Anderson localization in cold atom quantum quenches
Signatures of strong Anderson localization in the momentum distribution of a
cold atom cloud after a quantum quench are studied. We consider a quasi
one-dimensional cloud initially prepared in a well defined momentum state, and
expanding for some time in a disorder speckle potential. Anderson localization
leads to a formation of a coherence peak in the \emph{forward} scattering
direction (as opposed to the common weak localization backscattering peak). We
present a microscopic, and fully time resolved description of the phenomenon,
covering the entire diffusion--to--localization crossover. Our results should
be observable by present day technology.Comment: 4 pages, 2 figures, published versio
Echo spectroscopy of Anderson localization
We propose a conceptually new framework to study the onset of Anderson
localization in disordered systems. The idea is to expose waves propagating in
a random scattering environment to a sequence of short dephasing pulses. The
system responds through coherence peaks forming at specific echo times, each
echo representing a particular process of quantum interference. We suggest a
concrete realization for cold gases, where quantum interferences are observed
in the momentum distribution of matter waves in a laser speckle potential. This
defines a challenging, but arguably realistic framework promising to yield
unprecedented insight into the mechanisms of Anderson localization.Comment: 14 pages, 7 figures; published versio
Incoherent pair tunneling in the pseudogap phase of cuprates
Motivated by a recent experiment by Bergeal et al., we reconsider incoherent
pair tunneling in a cuprate junction formed from an optimally doped
superconducting lead and an underdoped normal metallic lead. We study the
impact of the pseudogap on the pair tunneling by describing fermions in the
underdoped lead with a model self-energy that has been developed to reproduce
photoemission data. We find that the pseudogap causes an additional temperature
dependent suppression of the pair contribution to the tunneling current. We
discuss consistency with available experimental data and propose future
experimental directions.Comment: 5 pages, 3 figure
Spin Hamiltonian of Hyperkagome Na4Ir3O8
We derive the spin Hamiltonian for the quantum spin liquid Na4Ir3O8, and then
estimate the direct and superexchange contributions between near neighbor
iridium ions using a tight binding parametrization of the electronic structure.
We find a magnitude of the exchange interaction comparable to experiment for a
reasonable value of the on-site Coulomb repulsion. For one of the two tight
binding parametrizations we have studied, the direct exchange term, which is
isotropic, dominates the total exchange. This provides support for those
theories proposed to describe this novel quantum spin liquid that assume an
isotropic Heisenberg model.Comment: 9 pages, 4 figure
Electronic Structure of Hyperkagome Na4Ir3O8
We investigate the electronic structure of the frustrated magnet Na4Ir3O8
using density functional theory. Due to strong spin-orbit coupling, the
hyperkagome lattice is characterized by a half-filled complex of states, making
it a cubic iridium analogue of the high temperature superconducting cuprates.
The implications of our results for this unique material are discussed.Comment: expanded discussion with extra figures - 6 pages, 10 figure
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