Enhanced correlations and superconductivity in weakly interacting partially flat-band systems: A determinantal quantum Monte Carlo study

Edwin W. Huang, Mohammad-Sadegh Vaezi, Zohar Nussinov, and Abolhassan Vaezi
Phys. Rev. B 99, 235128 – Published 13 June 2019

Abstract

Motivated by recent experiments realizing correlated phenomena and superconductivity in two-dimensional (2D) van der Waals devices, we consider the general problem of whether correlation effects may be enhanced by modifying band structure while keeping a fixed weak interaction strength. Using determinantal quantum Monte Carlo, we study the 2D Hubbard model for two different band structures: a regular nearest-neighbor tight-binding model and a partially flat-band structure containing a nondispersing region, with identical total noninteracting bandwidth Wtot. For both repulsive and attractive weak interactions (|U|Wtot), correlated phenomena are significantly stronger in the partially flat model. In the repulsive case, even with U being an order of magnitude smaller than Wtot, we find the presence of a Mott insulating state near half filling of the flat region in momentum space. In the attractive case, where generically the ground state is superconducting, the partially flat model exhibits significantly enhanced superconducting transition temperatures. These results suggest the possibility of engineering correlation effects in materials by tuning the noninteracting electronic dispersion.

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  • Received 25 November 2018
  • Revised 8 April 2019

DOI:https://doi.org/10.1103/PhysRevB.99.235128

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsGeneral PhysicsAtomic, Molecular & OpticalStatistical Physics & Thermodynamics

Authors & Affiliations

Edwin W. Huang1,2, Mohammad-Sadegh Vaezi3,4, Zohar Nussinov4, and Abolhassan Vaezi1,5,*

  • 1Department of Physics, Stanford University, Stanford, California 94305, USA
  • 2Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, California 94025, USA
  • 3Pasargad Institute for Advanced Innovative Solutions, Tehran 1991633361, Iran
  • 4Department of Physics, Washington University, St. Louis, Missouri 63160, USA
  • 5Stanford Center for Topological Quantum Physics, Stanford University, Stanford, California 94305, USA

  • *vaezi@stanford.edu

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Issue

Vol. 99, Iss. 23 — 15 June 2019

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