Eur. Phys. J. Special Topics 227, 1397–1404 (2018)
https://doi.org/10.1140/epjst/e2018-800090-y

Regular Article

Topological phase diagram of a Kitaev ladder

¹ Dipartimento di Fisica “E. R. Caianiello”, Università degli Studi di Salerno, Via Giovanni Paolo II, 84084 Fisciano (SA), Italy
² Spin-CNR, Università di Salerno, 84084 Fisciano (SA), Italy

^a e-mail: citro@sa.infn.it

Received: 8 May 2018
Received in final form: 7 August 2018
Published online: 29 November 2018

Abstract

We investigate the topological properties of a Kitaev ladder, i.e., a system made of two Kitaev chains coupled together by transversal hopping and pairing term, t₁ and Δ₁, respectively. Using the Chern number invariant, we present the topological phase diagram of the system. It is shown that beyond a non-topological phase, the system exhibits a topological phase either with four or two Majorana (zero energy) modes. In particular, we find that for some critical values of the transversal hopping t₁, and at a given transversal paring Δ₁, the topological phase survives also when the Kitaev criterion for the single chain (Δ > 0,   |μ| < 2t) is violated. Using a tight-binding analysis for a finite-size system we numerically check the bulk-edge correspondence.