Pairing Correlations across the Superfluid Phase Transition in the Unitary Fermi Gas

Jensen, Scott; Gilbreth, C. N.; Alhassid, Y.

doi:10.1103/physrevlett.124.090604

Cited by 31 publications

(32 citation statements)

References 65 publications

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“…[12] used the Luttinger-Ward approach, which contains uncontrolled systematic errors. However, this method has been shown to produce reliable results for other observables of the UFG [45,63]. Quantitatively, our results are above those of Ref.…”

supporting

confidence: 58%

“…Here we use an improved finite-temperature auxiliaryfield quantum Monte Carlo (AFMC) [43] method on a spatial lattice to calculate the temperature dependence of the contact across the superfluid transition for 40, 66, and 114 particles. Our AFMC method works in the canonical ensemble and uses an algorithm we recently introduced [44][45][46] that enables calculations for much larger lattices than would otherwise be feasible. For each of these particle numbers, we extrapolate to the continuum limit, eliminating systematic errors due to a finite filling factor (or equivalently finite effective range r e [47]).…”

mentioning

confidence: 99%

“…Results.-We performed AFMC simulations in the canonical ensemble as described in Ref. [45]. The simulations are carried out for N ¼ 40, 66, and 114 particles, on lattices of size N 3 L ¼ 5 3 ; 7 3 ; 9 3 ; 11 3 ; 13 3 , and 15 3 .…”

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confidence: 99%

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Contact in the Unitary Fermi Gas across the Superfluid Phase Transition

2020

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A quantity known as the contact is a fundamental thermodynamic property of quantum many-body systems with short-range interactions. Determination of the temperature dependence of the contact for the unitary Fermi gas of infinite scattering length has been a major challenge, with different calculations yielding qualitatively different results. Here we use finite-temperature auxiliary-field quantum Monte Carlo (AFMC) methods on the lattice within the canonical ensemble to calculate the temperature dependence of the contact for the homogeneous spin-balanced unitary Fermi gas. We extrapolate to the continuum limit for 40, 66, and 114 particles, eliminating systematic errors due to finite-range effects. We observe a dramatic decrease in the contact as the superfluid critical temperature is approached from below, followed by a gradual weak decrease as the temperature increases in the normal phase. Our theoretical results are in excellent agreement with the most recent precision ultracold atomic gas experiments. We also present results for the energy as a function of temperature in the continuum limit.

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confidence: 58%

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confidence: 99%

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Contact in the Unitary Fermi Gas across the Superfluid Phase Transition

2020

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“…Although the origin of the pseudogap strongly depends on the properties of each system, it is believed that the pseudogap is induced by fluctuation effects dominating nontrivial characters of the systems. Recently, an ultracold atomic gas provides us an ideal platform to study pseudogap physics and associated fluctuation effects in a systematic manner [21][22][23][24][25][26][27][28][29][30][31][32][33], thanks to the realization of the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein-condensation (BEC) crossover [34][35][36][37][38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Low-dimensional fluctuations and pseudogap in Gaudin-Yang Fermi gases

Tajima

Tsutsui

Doi

2020

Phys. Rev. Research

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The pseudogap is a ubiquitous phenomenon in strongly correlated systems, such as high-T c superconductors, ultracold atoms, and nuclear physics. Whereas pairing fluctuations inducing the pseudogap are known to be enhanced in low-dimensional systems, such effects have not been explored well in one of the most fundamental one-dimensional models, that is, Gaudin-Yang model. In this paper, we show how the pseudogap effect emerges in the single-particle excitation in this system using a diagrammatic approach. Fermionic single-particle spectra exhibit a unique crossover from the double-particle dispersion to the pseudogap state with increasing the attractive interaction and the number density at finite temperature. Surprisingly, our results of thermodynamic quantities in unpolarized and polarized gases show an excellent agreement with the recent quantum Monte Carlo and complex Langevin results, indicating the validity of our approach even in the region where the pseudogap appears.

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“…In spin- 1 2 systems with weak attractive interactions, for example, pairing of spin-up and spin-down particles at diametrically opposite points of the Fermi surface (i.e., Cooper pairing) typically leads to a superfluid phase at low enough temperatures, accompanied by the opening of an energy gap in the quasiparticle spectrum. Similar conclusions hold for strongly correlated systems, where pairing and superfluidity have been addressed thoroughly in theory [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and experiment [20][21][22][23][24][25][26][27][28][29][30]. A central open question in this regard is whether signatures of strong pairing fluctuations survive in the normal, non-superfluid high-temperature phase, which is often referred to as a "pseudogap regime", obtaining its name from a (potentially strong) suppression of the single-particle density of states around the Fermi surface.…”

Section: Introductionmentioning

confidence: 74%