Majorana and parafermion corner states from two coupled sheets of bilayer graphene

Dec 23, 2019
9 pages
Published in:
  • Phys.Rev.Res. 2 (2020) 1, 013330,
  • Phys.Rev.Research. 2 (2020) 013330
  • Published: Mar 17, 2020
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Abstract: (APS)
We consider a setup consisting of two coupled sheets of bilayer graphene in the regime of strong spin-orbit interaction, where electrostatic confinement is used to create an array of effective quantum wires. We show that for suitable interwire couplings the system supports a topological insulator phase exhibiting Kramers partners of gapless helical edge states, while the additional presence of a small in-plane magnetic field and weak proximity-induced superconductivity leads to the emergence of zero-energy Majorana corner states at all four corners of a rectangular sample, indicating the transition to a second-order topological superconducting phase. The presence of strong electron-electron interactions is shown to promote the above phases to their exotic fractional counterparts. In particular, we find that the system supports a fractional topological insulator phase exhibiting fractionally charged gapless edge states and a fractional second-order topological superconducting phase exhibiting zero-energy Z2m parafermion corner states, where m is an odd integer determined by the position of the chemical potential.