From Ising model to Kitaev Chain -- An introduction to topological phase transitions

TL;DR

This paper maps the one-dimensional transverse field Ising model to Kitaev's p-wave superconductor, revealing topological phase transitions, Majorana zero modes, and non-local order parameters relevant for topological quantum computing.

Contribution

It introduces a detailed mapping between the Ising model and Kitaev Chain, highlighting topological phases and Majorana modes, advancing understanding of topological quantum phase transitions.

Findings

Identification of topological invariant change at phase transition

Existence of Majorana zero modes in non-trivial phase

Mapping of non-local order parameter to Kitaev Chain

Abstract

In this general article, we map the one-dimensional transverse field quantum Ising model of ferromagnetism to Kitaev's one-dimensional p-wave superconductor, which has its application in fault-tolerant topological quantum computing. Mapping Pauli's spin operators of transverse Ising chain to spinless fermionic creation and annihilation operators by Inverse Jordan-Wigner transformation leads to a Hamiltonian form closely related to Kitaev Chain, which exhibits topological phase transition where phases are characterized by different topological invariant that changes discontinuously at the transition point. Kitaev Chain supports two Majorana zero modes (MZMs) in the non-trivial topological phase, while none is in the trivial phase. The doubly degenerate ground state of the transverse Ising in ferromagnetic phase corresponds to non-local free fermion degree made from MZMs. The quasi-particle excitations of Ising chain, viz., domain wall formation in the ferromagnetic phase and spin-flip in paramagnetic phase maps to Bogoliubon excitations. The mapping suggests that a non-local order parameter can be defined for Kitaev Chain to work with the usual paradigm of Landau's theory.