Universal Behavior of Pair Correlations in a Strongly Interacting Fermi Gas

Kuhnle, E. D.; Hu, Hui; Liu, Xia-Ji; Dyke, Paul; Mark, Manfred J.; Drummond, P. D.; Hannaford, Peter; Vale, Chris

doi:10.1103/physrevlett.105.070402

Cited by 196 publications

(233 citation statements)

References 39 publications

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“…This phenomenon, as well as the full structure of Að!Þ at k F jaj ) 1, can be understood as the result of a nontrivial interplay between two-body physics that involves the impurity and the hole near the bottom of the band, and the dynamics of multiple particle-hole excitations created at the Fermi surface. The possibility of a nontrivial interplay between many-body and few-body physics is a unique feature of ultracold-atom physics, and has attracted significant theoretical [86,87] and experimental [88] interest recently.…”

Section: Universal Radio-frequency Spectramentioning

confidence: 99%

Time-Dependent Impurity in Ultracold Fermions: Orthogonality Catastrophe and Beyond

et al. 2012

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The recent experimental realization of strongly imbalanced mixtures of ultracold atoms opens new possibilities for studying impurity dynamics in a controlled setting. In this paper, we discuss how the techniques of atomic physics can be used to explore new regimes and manifestations of Anderson's orthogonality catastrophe (OC), which could not be accessed in solid-state systems. Specifically, we consider a system of impurity atoms, localized by a strong optical-lattice potential, immersed in a sea of itinerant Fermi atoms. We point out that the Ramsey-interference-type experiments with the impurity atoms allow one to study the OC in the time domain, while radio-frequency (RF) spectroscopy probes the OC in the frequency domain. The OC in such systems is universal, not only in the long-time limit, but also for all times and is determined fully by the impurity-scattering length and the Fermi wave vector of the itinerant fermions. We calculate the universal Ramsey response and RF-absorption spectra. In addition to the standard power-law contributions, which correspond to the excitation of multiple particle-hole pairs near the Fermi surface, we identify a novel, important contribution to the OC that comes from exciting one extra particle from the bottom of the itinerant band. This contribution gives rise to a nonanalytic feature in the RF-absorption spectra, which shows a nontrivial dependence on the scattering length, and evolves into a true power-law singularity with the universal exponent 1=4 at the unitarity. We extend our discussion to spin-echo-type experiments, and show that they probe more complicated nonequilibirum dynamics of the Fermi gas in processes in which an impurity switches between states with different interaction strength several times; such processes play an important role in the Kondo problem, but remained out of reach in the solid-state systems. We show that, alternatively, the OC can be seen in the energy-counting statistics of the Fermi gas following a sudden quench of the impurity state. The energy distribution function, which can be measured in time-of-flight experiments, exhibits characteristic power-law singularities at low energies. Finally, systems in which the itinerant fermions have two or more hyperfine states provide an even richer playground for studying nonequilibrium impurity physics, allowing one to explore the nonequilibrium OC and even to simulate quantum transport through nanostructures. This provides a previously missing connection between cold atomic systems and mesoscopic quantum transport.

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Section: Universal Radio-frequency Spectramentioning

confidence: 99%

Time-Dependent Impurity in Ultracold Fermions: Orthogonality Catastrophe and Beyond

et al. 2012

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“…These can be experimentally tested, see [16,25,26,29,36]. In this section, we shall present a rigorous version of the Tan relations for the Hamiltonian H α constructed in the last subsection.…”

Section: Tan Relationsmentioning

confidence: 99%

Stability of a Fermionic N + 1 Particle System with Point Interactions

Moser

Seiringer

2017

Commun. Math. Phys.

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Abstract:We prove that a system of N fermions interacting with an additional particle via point interactions is stable if the ratio of the mass of the additional particle to the one of the fermions is larger than some critical m * . The value of m * is independent of N and turns out to be less than 1. This fact has important implications for the stability of the unitary Fermi gas. We also characterize the domain of the Hamiltonian of this model, and establish the validity of the Tan relations for all wave functions in the domain.

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“…In the near future, we are interested in investigating the virial expansion of the Tan's contact [41,42], the three-body recombination rate [43,44], and the quantum viscosity [45,46].…”

Section: Conclusion and Remarksmentioning

confidence: 99%

Virial expansion for a strongly correlated Fermi gas with imbalanced spin populations

Liu

2010

Phys. Rev. A

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Quantum virial expansion provides an ideal tool to investigate the high-temperature properties of a strongly correlated Fermi gas. Here, we construct the virial expansion in the presence of spin population imbalance. Up to the third order, we calculate the high-temperature free energy of a unitary Fermi gas as a function of spin imbalance, with infinitely large, attractive or repulsive interactions. In the latter repulsive case, we show that there is no itinerant ferromagnetism when quantum virial expansion is applicable. We therefore estimate an upper bound for the ferromagnetic transition temperature Tc. For a harmonically trapped Fermi gas at unitarity, we find that (Tc)uppper < TF , where TF is the Fermi temperature at the center of the trap. Our result for the high-temperature equations of state may confront future high-precision thermodynamic measurements.

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Universal Behavior of Pair Correlations in a Strongly Interacting Fermi Gas

Cited by 196 publications

References 39 publications

Time-Dependent Impurity in Ultracold Fermions: Orthogonality Catastrophe and Beyond

Time-Dependent Impurity in Ultracold Fermions: Orthogonality Catastrophe and Beyond

Stability of a Fermionic N + 1 Particle System with Point Interactions

Virial expansion for a strongly correlated Fermi gas with imbalanced spin populations

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