18 research outputs found
The impact of the injection protocol on an impurity's stationary state
We examine stationary state properties of an impurity particle injected into
a one-dimensional quantum gas. We show that the value of the impurity's end
velocity lies between zero and the speed of sound in the gas, and is determined
by the injection protocol. This way, the impurity's constant motion is a
dynamically emergent phenomenon whose description goes beyond accounting for
the kinematic constraints of Landau approach to superfluidity. We provide exact
analytic results in the thermodynamic limit, and perform finite-size numerical
simulations to demonstrate that the predicted phenomena are within the reach of
the existing ultracold gases experiments.Comment: main text+supplemental, 14 pages, 3 figures; v2: title, introduction,
and summary modified, 3 refs. adde
Finite temperature spin diffusion in the Hubbard model in the strong coupling limit
We investigate finite temperature spin transport in one spatial dimension by
considering the spin-spin correlation function of the Hubbard model in the
limiting case of infinitely strong repulsion. We find that in the absence of
bias the transport is diffusive, and derive the spin diffusion constant. Our
approach is based on asymptotic analysis of a Fredholm determinant
representation. The obtained results are in agreement with Generalized
Hydrodynamics approach.Comment: 30 pages, 1 figur
Dynamical quantum Cherenkov transition of fast impurities in quantum liquids
The challenge of understanding the dynamics of a mobile impurity in an
interacting quantum many-body medium comes from the necessity of including
entanglement between the impurity and excited states of the environment in a
wide range of energy scales. In this paper, we investigate the motion of a
finite mass impurity injected into a three-dimensional quantum Bose fluid as it
starts shedding Bogoliubov excitations. We uncover a transition in the dynamics
as the impurity's velocity crosses a critical value which depends on the
strength of the interaction between the impurity and bosons as well as the
impurity's recoil energy. We find that in injection experiments, the two
regimes differ not only in the character of the impurity velocity abatement,
but also exhibit qualitative differences in the Loschmidt echo, density ripples
excited in the BEC, and momentum distribution of scattered bosonic particles.
The transition is a manifestation of a dynamical quantum Cherenkov effect, and
should be experimentally observable with ultracold atoms using Ramsey
interferometry, RF spectroscopy, absorption imaging, and time-of-flight
imaging.Comment: 5 pages, 3 figures + 4 pages, 3 figure
Recommended from our members
Quantum Flutter: Signatures and Robustness
We investigate the motion of an impurity particle injected with finite velocity into an interacting one-dimensional quantum gas. Using large-scale numerical simulations based on matrix product states, we observe and quantitatively analyze long-lived oscillations of the impurity momentum around a nonzero saturation value, called quantum flutter. We show that the quantum flutter frequency is equal to the energy difference between two branches of collective excitations of the model. We propose an explanation of the finite saturation momentum of the impurity based on the properties of the edge of the excitation spectrum. Our results indicate that quantum flutter exists away from integrability and provide parameter regions in which it could be observed in experiments with ultracold atoms using currently available technology.Physic
Statics and dynamics of weakly coupled antiferromagnetic spin-1/2 ladders in a magnetic field
We investigate weakly coupled spin-1/2 ladders in a magnetic field. The work
is motivated by recent experiments on the compound (C5H12N)2CuBr4 (BPCB). We
use a combination of numerical and analytical methods, in particular the
density matrix renormalization group (DMRG) technique, to explore the phase
diagram and the excitation spectra of such a system. We give detailed results
on the temperature dependence of the magnetization and the specific heat, and
the magnetic field dependence of the nuclear magnetic resonance (NMR)
relaxation rate of single ladders. For coupled ladders, treating the weak
interladder coupling within a mean-field or quantum Monte Carlo approach, we
compute the transition temperature of triplet condensation and its
corresponding antiferromagnetic order parameter. Existing experimental
measurements are discussed and compared to our theoretical results. Furthermore
we compute, using time dependent DMRG, the dynamical correlations of a single
spin ladder. Our results allow to directly describe the inelastic neutron
scattering cross section up to high energies. We focus on the evolution of the
spectra with the magnetic field and compare their behavior for different
couplings. The characteristic features of the spectra are interpreted using
different analytical approaches such as the mapping onto a spin chain, a
Luttinger liquid (LL) or onto a t-J model. For values of parameters for which
such measurements exist, we compare our results to inelastic neutron scattering
experiments on the compound BPCB and find excellent agreement. We make
additional predictions for the high energy part of the spectrum that are
potentially testable in future experiments.Comment: 35 pages, 26 figure
Quantum flutter of supersonic particles in one-dimensional quantum liquids
The non-equilibrium dynamics of strongly correlated many-body systems
exhibits some of the most puzzling phenomena and challenging problems in
condensed matter physics. Here we report on essentially exact results on the
time evolution of an impurity injected at a finite velocity into a
one-dimensional quantum liquid. We provide the first quantitative study of the
formation of the correlation hole around a particle in a strongly coupled
many-body quantum system, and find that the resulting correlated state does not
come to a complete stop but reaches a steady state which propagates at a finite
velocity. We also uncover a novel physical phenomenon when the impurity is
injected at supersonic velocities: the correlation hole undergoes long-lived
coherent oscillations around the impurity, an effect we call quantum flutter.
We provide a detailed understanding and an intuitive physical picture of these
intriguing discoveries, and propose an experimental setup where this physics
can be realized and probed directly.Comment: 13 pages, 9 figure
Processing and properties of fibre reinforced silicon carbide composites
SIGLEAvailable from British Library Document Supply Centre-DSC:DXN030325 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Reentrant behavior of the breathing-mode-oscillation frequency in a one-dimensional Bose gas
Exciting temporal oscillations of the density distribution is a high-precision method for probing ultracold trapped atomic gases. Interaction effects in their many-body dynamics are particularly puzzling and counter-intuitive in one spatial dimension (1D) due to enhanced quantum correlations. We consider 1D quantum Bose gas in a parabolic trap at zero temperature and explain, analytically and numerically, how oscillation frequency depends on the number of particles, their repulsion, and the trap strength. We identify the frequency with the energy difference between the ground state and a particular excited state. This way we avoided resolving the dynamical evolution of the system, simplifying the problem immensely. We find an excellent quantitative agreement of our results with the data from the Innsbruck experiment [Science 325, 1224 (2009)].Peer Reviewe