Dynamical Spectra of Spin Supersolid States in Triangular Antiferromagnets

TL;DR

This study uses tensor network renormalization to analyze the dynamical spectra of spin supersolid states in triangular antiferromagnets, revealing distinct magnon modes and their evolution under magnetic fields.

Contribution

It provides the first detailed dynamical spectral analysis of spin supersolid states in triangular antiferromagnets using tensor network methods.

Findings

Identifies gapless Goldstone and gapped magnon modes.

Shows roton modes near the M point at zero field.

Reveals roton mode disappearance in the V-shape supersolid phase.

Abstract

We employ tensor network renormalization to explore the dynamical spectra of the easy-axis triangular-lattice antiferromagnet (TLAF) in a magnetic field. Our analysis identifies two distinct low-energy magnon excitations: a gapless Goldstone mode and a gapped mode. At zero field, the spectra display two nearly degenerate roton modes near the M point. With the increase of the magnetic field within the Y-shape superfluid phase, these modes diverge, with the roton excitation vanishing from the Goldstone mode branch, suggesting that the roton dip in this mode may just result from the energy-level repulsion imposed by the roton excitation in the gapped mode. Moreover, the in-plane spectral function shows substantial weight in high energies in the same spin excitation channel where the low-energy roton excitation appears. However, these roton excitations are absent in the V-shape supersolid phase.