Stoner ferromagnetism of a strongly interacting Fermi gas in the quasirepulsive regime

Lianyi He, Xia-Ji Liu, Xu-Guang Huang, and Hui Hu
Phys. Rev. A 93, 063629 – Published 24 June 2016

Abstract

Recent advances in rapidly quenched ultracold atomic Fermi gases near a Feshbach resonance have brought about a number of interesting problems in the context of observing the long-sought Stoner ferromagnetic phase transition. The possibility of experimentally obtaining a “quasirepulsive” regime in the upper branch of the energy spectrum due to the rapid quench is currently being debated, and the Stoner transition has mainly been investigated theoretically by using perturbation theory or at high polarization due to the limited theoretical approaches in the strongly repulsive regime. In this work, we present a nonperturbative theoretical approach to the quasirepulsive upper branch of a Fermi gas near a broad Feshbach resonance, and we determine the finite-temperature phase diagram for the Stoner instability. Our results agree well with the known quantum Monte Carlo simulations at zero temperature, and we recover the known virial expansion prediction at high temperature for arbitrary interaction strengths. At resonance, we find that the Stoner transition temperature becomes of the order of the Fermi temperature, around which the molecule formation rate becomes vanishingly small. This suggests a feasible way to observe Stoner ferromagnetism in the nondegenerate temperature regime.

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  • Received 31 May 2016

DOI:https://doi.org/10.1103/PhysRevA.93.063629

©2016 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Authors & Affiliations

Lianyi He1,2, Xia-Ji Liu3, Xu-Guang Huang4, and Hui Hu3

  • 1Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
  • 2Department of Physics and Collaborative Innovation Center for Quantum Matter, Tsinghua University, Beijing 100084, China
  • 3Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne 3122, Australia
  • 4Physics Department and Center for Particle Physics and Field Theory, Fudan University, Shanghai 200433, China

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Issue

Vol. 93, Iss. 6 — June 2016

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