Dynamical structure factor of a fermionic supersolid on an optical lattice

Ettore Vitali, Patrick Kelly, Annette Lopez, Gianluca Bertaina, and Davide Emilio Galli
Phys. Rev. A 102, 053324 – Published 30 November 2020

Abstract

Interfacing unbiased quantum Monte Carlo simulations with state-of-the-art analytic continuation techniques, we obtain exact numerical results for dynamical density and spin correlations in the attractive Hubbard model, describing a spin-balanced two-dimensional cold Fermi gas on an optical lattice. We focus on half-filling, where on average one fermion occupies each lattice site, and the system displays an intriguing supersolid phase: a superfluid with a checkerboard density modulation. The coexistence of U(1) broken symmetry and the density modulations makes this regime very challenging and interesting for the calculation of dynamical properties. We compare our unbiased results with state-of-the-art generalized random phase approximation calculations: both approaches agree on a well-defined low-energy Nambu-Goldstone collective mode in the density correlations, while the higher energy structures appear to differ significantly. We also observe an interesting high-energy spin mode. We argue that our results provide a robust benchmark for generalized random phase approximation techniques, which are widely considered to be the method of choice for dynamical correlations in Fermi gases. Also, our calculations yield new physical insight into the high-energy behavior of the dynamical structure factor of the attractive Hubbard model, which is a well known prototype lattice model for superconductors and is a fertile field to target the observation of collective modes in strongly correlated systems.

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  • Received 30 January 2020
  • Accepted 16 November 2020

DOI:https://doi.org/10.1103/PhysRevA.102.053324

©2020 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Ettore Vitali1,2, Patrick Kelly1, Annette Lopez1,3, Gianluca Bertaina4,5, and Davide Emilio Galli4

  • 1Department of Physics, California State University Fresno, Fresno, California 93740, USA
  • 2Department of Physics, The College of William and Mary, Williamsburg, Virginia 23187, USA
  • 3Department of Physics, Brown University, Providence, Rhode Island 02912, USA
  • 4Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy
  • 5Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy

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Issue

Vol. 102, Iss. 5 — November 2020

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