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Two-step gap opening across the quantum critical point in a Kitaev honeycomb magnet

Authors :
Nagai, Y.
Jinno, T.
Yoshitake, Y.
Nasu, J.
Motome, Y.
Itoh, M.
Shimizu, Y.
Source :
Phys. Rev. B 101, 020414 (2020)
Publication Year :
2018

Abstract

Quantum spin liquid involves fractionalized quasipariticles such as spinons and visons. They are expressed as itinerant Majorana fermions and $Z_2$ fluxes in the Kitaev model with bond-dependent exchange interactions on a honeycomb spin lattice. The observation has recently attracted attention for a candidate material $\alpha$-RuCl$_3$, showing spin liquid behaviour induced by a magnetic field. Since the observable spin excitation is inherently composed of the two quasiparticles, which further admix each other by setting in the magnetic field as well as non-Kitaev interactions, their individual identification remains challenging. Here we report an emergent low-lying spin excitation through nuclear magnetic and quadrupole resonance measurements down to $\sim 0.4$ K corresponding to $1/500$ of the exchange energy under the finely tuned magnetic field across the quantum critical point. We determined the critical behaviour of low-lying excitations and found evolution of two kinds of the spin gap at high fields. The two excitations exhibit repulsive magnetic field dependence, suggesting anti-crossing due to the hybridization between fractionalized quasiparticles.<br />Comment: 5 pages, 4 figures

Details

Database :
arXiv
Journal :
Phys. Rev. B 101, 020414 (2020)
Publication Type :
Report
Accession number :
edsarx.1810.05379
Document Type :
Working Paper
Full Text :
https://doi.org/10.1103/PhysRevB.101.020414