1,499 research outputs found
Momentum distribution dynamics of a Tonks-Girardeau gas: Bragg reflections of a quantum many-body wavepacket
The dynamics of the momentum distribution and the reduced single-particle
density matrix (RSPDM) of a Tonks-Girardeau (TG) gas is studied in the context
of Bragg-reflections of a many-body wavepacket. We find strong suppression of a
Bragg-reflection peak for a dense TG wavepacket; our observation illustrates
dependence of the momentum distribution on the interactions/wavefunction
symmetry. The momentum distribution is calculated with a fast algorithm based
on a formula expressing the RSPDM via a dynamically evolving single-particle
basis
Four-dimensional photonic lattices and discrete tesseract solitons
We theoretically study discrete photonic lattices in more than three
dimensions and point out that such systems can exist in continuous
three-dimensional (3D) space. We study discrete diffraction in the linear
regime, and predict the existence of four-dimensional (4D) tesseract solitons
in nonlinear 4D periodic photonic lattices. Finally, we propose a design
towards a potential realization of such periodic 4D lattices in experiments.Comment: Submitted to PRL on 14 May 201
Transverse electric plasmons in bilayer graphene
We predict the existence of transverse electric (TE) plasmons in bilayer
graphene. We find that their plasmonic properties are much more pronounced in
bilayer than in monolayer graphene, in a sense that they can get more localized
at frequencies just below ~eV for adequate doping values. This
is a consequence of the perfectly nested bands in bilayer graphene which are
separated by ~eV
Screening effect on the optical absorption in graphene and metallic monolayers
Screening is one of the fundamental concepts in solid state physics. It has a
great impact on the electronic properties of graphene where huge mobilities
were observed in spite of the large concentration of charged impurities. While
static screening has successfully explained DC mobilities, screening properties
can be significantly changed at infrared or optical frequencies. In this paper
we discuss the influence of dynamical screening on the optical absorption of
graphene and other 2D electron systems like metallic monolayers. This research
is motivated by recent experimental results which pointed out that graphene
plasmon linewidths and optical scattering rates can be much larger than
scattering rates determined by DC mobilities. Specifically we discuss a process
where a photon incident on a graphene plane can excite a plasmon by scattering
from an impurity, or surface optical phonon of the substrate.Comment: 19 pages, 2 figure
Ground state properties of a one-dimensional strongly-interacting Bose-Fermi mixture in a double-well potential
We calculate the reduced single-particle density matrix (RSPDM), momentum
distributions, natural orbitals and their occupancies, for a strongly
interacting one-dimensional Bose-Fermi mixture in a double-well potential with
a large central barrier. For mesoscopic systems, we find that the ground state
properties qualitatively differ for mixtures with even number of particles
(both odd-odd and even-even mixtures) in comparison to mixtures with odd
particle numbers (odd-even and even-odd mixtures). For even mixtures the
momentum distribution is smooth, whereas the momentum distribution of odd
mixtures possesses distinct modulations; the differences are observed also in
the off-diagonal correlations of the RSPDM, and in the occupancies of natural
orbitals. The calculation is based on a derived formula which enables efficient
calculation of the RSPDM for mesoscopic mixtures in various potentials.Comment: 10 figure
Free expansion of a Lieb-Liniger gas: Asymptotic form of the wave functions
The asymptotic form of the wave functions describing a freely expanding
Lieb-Liniger gas is derived by using a Fermi-Bose transformation for
time-dependent states, and the stationary phase approximation. We find that
asymptotically the wave functions approach the Tonks-Girardeau (TG) structure
as they vanish when any two of the particle coordinates coincide. We point out
that the properties of these asymptotic states can significantly differ from
the properties of a TG gas in a ground state of an external potential. The
dependence of the asymptotic wave function on the initial state is discussed.
The analysis encompasses a large class of initial conditions, including the
ground states of a Lieb-Liniger gas in physically realistic external
potentials. It is also demonstrated that the interaction energy asymptotically
decays as a universal power law with time, .Comment: Section VI added to v2; published versio
Lieb-Liniger gas in a constant force potential
We use Gaudin's Fermi-Bose mapping operator to calculate exact solutions for
the Lieb-Liniger model in a linear (constant force) potential (the constructed
exact stationary solutions are referred to as the Lieb-Liniger-Airy wave
functions). The ground state properties of the gas in the wedge-like trapping
potential are calculated in the strongly interacting regime by using
Girardeau's Fermi-Bose mapping and the pseudopotential approach in the
-approximation ( denotes the strength of the interaction). We point out
that quantum dynamics of Lieb-Liniger wave packets in the linear potential can
be calculated by employing an -dimensional Fourier transform as in the case
of free expansion
The pinning quantum phase transition in a Tonks Girardeau gas: diagnostics by ground state fidelity and the Loschmidt echo
We study the pinning quantum phase transition in a Tonks-Girardeau gas, both
in equilibrium and out-of-equilibrium, using the ground state fidelity and the
Loschmidt echo as diagnostic tools. The ground state fidelity (GSF) will have a
dramatic decrease when the atomic density approaches the commensurate density
of one particle per lattice well. This decrease is a signature of the pinning
transition from the Tonks to the Mott insulating phase. We study the
applicability of the fidelity for diagnosing the pinning transition in
experimentally realistic scenarios. Our results are in excellent agreement with
recent experimental work. In addition, we explore the out of equilibrium
dynamics of the gas following a sudden quench with a lattice potential. We find
all properties of the ground state fidelity are reflected in the Loschmidt echo
dynamics i.e., in the non equilibrium dynamics of the Tonks-Girardeau gas
initiated by a sudden quench of the lattice potential
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