Solitonic spin-liquid state due to the violation of the Lifshitz condition in Fe$_{1+y}$Te

TL;DR

This paper reveals an unconventional magnetic transition in Fe$_{1+y}$Te with high Fe excess, characterized by a liquid-like precursor state and solitonic spin-liquid phases due to Lifshitz condition violation.

Contribution

It demonstrates that in Fe$_{1+y}$Te, the incommensurate SDW order arises from Lifshitz condition violation, leading to novel solitonic spin-liquid states.

Findings

Liquid-like magnetic precursor observed above transition

Incommensurate SDW order described by Lifshitz violation

Multiple Lifshitz invariants induce solitonic phases

Abstract

A combination of phenomenological analysis and M\"ossbauer spectroscopy experiments on the tetragonal Fe$_{1+y}$Te system indicates that the magnetic ordering transition in compounds with higher Fe-excess, $y\ge$ 0.11, is unconventional. Experimentally, a liquid-like magnetic precursor with quasi-static spin-order is found from significantly broadened M\"ossbauer spectra at temperatures above the antiferromagnetic transition. The incommensurate spin-density wave (SDW) order in Fe$_{1+y}$Te is described by a magnetic free energy that violates the weak Lifshitz condition in the Landau theory of second-order transitions. The presence of multiple Lifshitz invariants provides the mechanism to create multidimensional, twisted, and modulated solitonic phases.