Spectra of a Gapped Quantum Spin Liquid with a Strong Chiral Excitation on the Triangular Lattice

TL;DR

This paper uses exact diagonalization to analyze the dynamical properties of a gapped quantum spin liquid on a triangular lattice, revealing distinct spectral features and a strong chiral excitation mode.

Contribution

It provides detailed spectral signatures of a gapped QSL phase and identifies a prominent chiral excitation mode, advancing understanding of its excitations and experimental detection.

Findings

QSL phase exhibits gapped spectra in spin structure factor and Raman susceptibility.

Distinct spectral features differentiate the QSL from neighboring phases.

Presence of a strong chiral excitation mode in the Raman A2 channel.

Abstract

While a quantum spin liquid (QSL) phase has been identified in the $J_1$-$J_2$ Heisenberg model on a triangular lattice via numerical calculations, debate persists about whether or not such a QSL is gapped or gapless, with contradictory conclusions from different techniques. Moreover, information about excitations and dynamics is crucial for the experimental detection of such a phase. In this work, we use exact diagonalization to characterize signatures of a QSL phase on the triangular lattice through the dynamical spin structure factor $\mathcal{S}(q,\omega)$ and Raman susceptibility $\mathcal{\chi}(\omega)$. We find that spectra for the QSL phase show distinct features compared to those of neighboring phases; and both the Raman spectra and spin structure factor show gapped behaviour in the QSL phase. Interestingly, there is a prominent excitation mode in the Raman $A_2$ channel, indicating a strong subleading tendency toward a chiral spin liquid phase.