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Title: String-theory-based predictions for nonhydrodynamic collective modes in strongly interacting Fermi gases

Authors:
; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1328510
Grant/Contract Number:
SC0008132; SC0011090
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review A
Additional Journal Information:
Journal Volume: 94; Journal Issue: 3; Related Information: CHORUS Timestamp: 2016-09-19 18:09:04; Journal ID: ISSN 2469-9926
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English

Citation Formats

Bantilan, H., Brewer, J. T., Ishii, T., Lewis, W. E., and Romatschke, P.. String-theory-based predictions for nonhydrodynamic collective modes in strongly interacting Fermi gases. United States: N. p., 2016. Web. doi:10.1103/PhysRevA.94.033621.
Bantilan, H., Brewer, J. T., Ishii, T., Lewis, W. E., & Romatschke, P.. String-theory-based predictions for nonhydrodynamic collective modes in strongly interacting Fermi gases. United States. doi:10.1103/PhysRevA.94.033621.
Bantilan, H., Brewer, J. T., Ishii, T., Lewis, W. E., and Romatschke, P.. Mon . "String-theory-based predictions for nonhydrodynamic collective modes in strongly interacting Fermi gases". United States. doi:10.1103/PhysRevA.94.033621.
@article{osti_1328510,
title = {String-theory-based predictions for nonhydrodynamic collective modes in strongly interacting Fermi gases},
author = {Bantilan, H. and Brewer, J. T. and Ishii, T. and Lewis, W. E. and Romatschke, P.},
abstractNote = {},
doi = {10.1103/PhysRevA.94.033621},
journal = {Physical Review A},
number = 3,
volume = 94,
place = {United States},
year = {Mon Sep 19 00:00:00 EDT 2016},
month = {Mon Sep 19 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevA.94.033621

Citation Metrics:
Cited by: 2works
Citation information provided by
Web of Science

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  • We consider one-dimensional interacting Bose-Fermi mixture with equal masses of bosons and fermions, and with equal and repulsive interactions between Bose-Fermi and Bose-Bose particles. Such a system can be realized in current experiments with ultracold Bose-Fermi mixtures. We apply the Bethe ansatz technique to find the exact ground state energy at zero temperature for any value of interaction strength and density ratio between bosons and fermions. We use it to prove the absence of the demixing, contrary to prediction of a mean-field approximation. Combining exact solution with local density approximation in a harmonic trap, we calculate the density profiles andmore » frequencies of collective modes in various limits. In the strongly interacting regime, we predict the appearance of low-lying collective oscillations which correspond to the counterflow of the two species. In the strongly interacting regime, we use exact wavefunction to calculate the single particle correlation functions for bosons and fermions at low temperatures under periodic boundary conditions. Fourier transform of the correlation function is a momentum distribution, which can be measured in time-of-flight experiments or using Bragg scattering. We derive an analytical formula, which allows to calculate correlation functions at all distances numerically for a polynomial time in the system size. We investigate numerically two strong singularities of the momentum distribution for fermions at k {sub f} and k {sub f} + 2k {sub b}. We show, that in strongly interacting regime correlation functions change dramatically as temperature changes from 0 to a small temperature {approx}E {sub f}/{gamma} << E {sub f}, where E {sub f} = ({pi}hn){sup 2}/(2m), n is the total density and {gamma} = mg/(h {sup 2} n) >> 1 is the Lieb-Liniger parameter. A strong change of the momentum distribution in a small range of temperatures can be used to perform a thermometry at very small temperatures.« less
  • The zero-temperature properties of a dilute two-component Fermi gas in the BCS to Bose-Einstein Condensation crossover are investigated. On the basis of a generalization of the Hylleraas-Undheim method, we construct rigorous upper bounds to the collective frequencies for the radial and the axial breathing mode of the Fermi gas under harmonic confinement in the framework of the hydrodynamic theory. The bounds are compared to experimental data for trapped vapors of {sup 6}Li atoms.
  • Theoretical predictions for the dynamic structure factor of a harmonically trapped Fermi superfluid near the Bose-Einstein condensate-Bardeen-Cooper-Schrieffer (BEC-BCS) crossover are compared with recent Bragg spectroscopy measurements at large transferred momenta. The calculations are based on a random-phase (or time-dependent Hartree-Fock-Gorkov) approximation generalized to the strongly interacting regime. Excellent agreement with experimental spectra at low temperatures is obtained, with no free parameters. Theoretical predictions for zero-temperature static structure factor are also found to agree well with the experimental results and independent theoretical calculations based on the exact Tan relations. The temperature dependence of the structure factors at unitarity is predicted.
  • We study the relationship between Tan's contact parameter and the macroscopic dynamic properties of an ultracold trapped gas, such as the frequencies of the collective oscillations and the propagation of sound in one-dimensional (1D) configurations. We find that the value of the contact, extracted from the most recent low-temperature measurements of the equation of state near unitarity, reproduces with accuracy the experimental values of the collective frequencies of the radial breathing mode at the lowest temperatures. The available experiment results for the 1D sound velocities near unitarity are also investigated.