From confined spinons to emergent fermions: Observation of elementary magnetic excitations in a transverse-field Ising chain

TL;DR

This study investigates magnetic excitations in a transverse-field Ising chain compound, revealing confined spinons at zero field and emergent fermionic modes under high transverse magnetic fields, demonstrating quantum phase transitions and emergent phenomena.

Contribution

It provides the first detailed spectroscopy observation of confined spinons and emergent fermions in a real material, confirming theoretical predictions of 1D quantum spin models.

Findings

Confined spinons observed below 5 K in zero field.

Quantum disordered phase appears at 7 T with emergent fermions.

Spin dynamic structure factor matches 1D XXZ model predictions.

Abstract

We report on spectroscopy study of elementary magnetic excitations in an Ising-like antiferromagnetic chain compound SrCo$_2$V$_2$O$_8$ as a function of temperature and applied transverse magnetic field up to 25 T. An optical as well as an acoustic branch of confined spinons, the elementary excitations at zero field, are identified in the antiferromagnetic phase below the N\'{e}el temperature of 5 K and described by a one-dimensional Schr\"{o}dinger equation. The confinement can be suppressed by an applied transverse field and a quantum disordered phase is induced at 7 T. In this disordered paramagnetic phase, we observe three emergent fermionic excitations with different transverse-field dependencies. The nature of these modes is clarified by studying spin dynamic structure factor of a 1D transverse-field Heisenberg-Ising (XXZ) model using the method of infinite time evolving block decimation. Our work reveals emergent quantum phenomena and provides a concrete system for testifying theoretical predications of one-dimension quantum spin models.