215 research outputs found
Pressure, compressibility, and contact of the two-dimensional attractive Fermi gas
Using ab initio lattice methods, we calculate the finite temperature
thermodynamics of homogeneous two-dimensional spin-1/2 fermions with attractive
short-range interactions. We present results for the density, pressure,
compressibility, and quantum anomaly (i.e. Tan's contact) for a wide range of
temperatures and coupling strengths, focusing on the unpolarized case. Within
our statistical and systematic uncertainties, our prediction for the density
equation of state differs quantitatively from the prediction by Luttinger-Ward
theory in the strongly coupled region of parameter space, but otherwise agrees
well with it. We also compare our calculations with the second- and third-order
virial expansion, with which they are in excellent agreement in the
low-fugacity regime.Comment: 7 pages, 8 figures, including supplemental material
Dynamics of entanglement entropy of interacting fermions in a 1D driven harmonic trap
Following up on a recent analysis of two cold atoms in a time-dependent
harmonic trap in one dimension, we explore the entanglement entropy of two and
three fermions in the same situation when driven through a parametric
resonance. We find that the presence of such a resonance in the two-particle
system leaves a clear imprint on the entanglement entropy. We show how the
signal is modified by attractive and repulsive contact interactions, and how it
remains present for the three-particle system. Additionaly, we extend the work
of recent experiments to demonstrate how restricting observation to a limited
subsystem gives rise to locally thermal behavior.Comment: Proceedings of Lattice2017, Granada, Spai
Spin 1/2 Fermions in the Unitary Regime at Finite Temperature
We have performed a fully non-perturbative calculation of the thermal
properties of a system of spin 1/2 fermions in 3D in the unitary regime. We
have determined the critical temperature for the superfluid-normal phase
transition. The thermodynamic behavior of this system presents a number of
unexpected features, and we conclude that spin 1/2 fermions in the BCS-BEC
crossover should be classified as a new type of superfluid.Comment: 6 pages, 2 figures, version for the Proceedings of QMBT1
Thermodynamics of a Trapped Unitary Fermi Gas
We present the first model-independent comparison of recent measurements of
the entropy and of the critical temperature of a unitary Fermi gas, performed
by Luo et al., with the most complete results currently available from finite
temperature Monte Carlo calculations. The measurement of the critical
temperature in a cold fermionic atomic cloud is consistent with a value
in the bulk, as predicted by the present authors in
their Monte Carlo calculations.Comment: 5 pages, 4 figures, published versio
Universality in one-dimensional fermions at finite temperature: Density, pressure, compressibility, and contact
We present finite-temperature, lattice Monte Carlo calculations of the
particle number density, compressibility, pressure, and Tan's contact of an
unpolarized system of short-range, attractively interacting spin-1/2 fermions
in one spatial dimension, i.e., the Gaudin-Yang model. In addition, we compute
the second-order virial coefficients for the pressure and the contact, both of
which are in excellent agreement with the lattice results in the low-fugacity
regime. Our calculations yield universal predictions for ultracold atomic
systems with broad resonances in highly constrained traps. We cover a wide
range of couplings and temperatures and find results that support the existence
of a strong-coupling regime in which the thermodynamics of the system is
markedly different from the noninteracting case. We compare and contrast our
results with identical systems in higher dimensions.Comment: 6 pages, 7 figures; improved, published versio
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