# Majorana-Magnon Crossover by a Magnetic Field in the Kitaev Model: Continuous-Time Quantum Monte Carlo Study

## TL;DR

This study uses large-scale quantum Monte Carlo simulations to explore how magnetic fields influence Majorana fermions and magnons in the Kitaev model, revealing a broad paramagnetic phase and confinement-deconfinement behavior.

## Contribution

It provides the first unbiased numerical analysis of the finite-temperature and magnetic field effects on Majorana fermions in the Kitaev model.

## Key findings

- Unconventional paramagnetic region persists at finite temperature.
- Fractional spin dynamics extend beyond zero-temperature topological phase.
- Evidence of confinement-deconfinement transition between Majorana fermions and magnons.

## Abstract

Kitaev quantum spin liquids host Majorana fermions via the fractionalization of spins. In a magnetic field, the Majorana fermions were predicted to comprise a topological state, which has attracted great attention by the discovery of the half-quantized thermal Hall conductivity. Nevertheless, a reliable theory remains elusive for the field effect, especially at finite temperature. Here we present unbiased large-scale numerical results for the Kitaev model in a wide range of magnetic field and temperature. We find that the unconventional paramagnetic region showing fractional spin dynamics extends at finite temperature, far beyond the field range where the topological state is expected at zero temperature. Our results show the confinement-deconfinement behavior between the fractional Majorana excitations and the conventional magnons.