Enhancing the stability of a fractional Chern insulator against competing phases

Adolfo G. Grushin, Titus Neupert, Claudio Chamon, and Christopher Mudry
Phys. Rev. B 86, 205125 – Published 21 November 2012

Abstract

We construct a two-band lattice model whose bands can carry the Chern numbers C=0,±1,±2. By means of numerical exact diagonalization, we show that the most favorable situation that selects fractional Chern insulators (FCIs) is not necessarily the one that mimics Landau levels, namely a flat band with Chern number 1. First, we find that the gap, measured in units of the on-site electron-electron repulsion, can increase by almost two orders of magnitude when the bands are flat and carry a Chern number C=2 instead of C=1. Second, we show that giving a width to the bands can help to stabilize a FCI. Finally, we put forward a tool to characterize the real-space density profile of the ground state that is useful to distinguish FCI from other competing phases of matter supporting charge density waves or phase separation.

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  • Received 27 July 2012

DOI:https://doi.org/10.1103/PhysRevB.86.205125

©2012 American Physical Society

Authors & Affiliations

Adolfo G. Grushin1,2, Titus Neupert3, Claudio Chamon2, and Christopher Mudry3

  • 1Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid, Spain
  • 2Physics Department, Boston University, Boston, Massachusetts 02215, USA
  • 3Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland

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Issue

Vol. 86, Iss. 20 — 15 November 2012

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