Low-Temperature Dynamical Structure Factor of the Two-Leg Spin-1/2 Heisenberg Ladder

TL;DR

This paper investigates the low-temperature dynamical structure factor of a two-leg spin-1/2 Heisenberg ladder, revealing temperature-dependent broadening, asymmetry of the triplon mode, and a novel resonance similar to the Villain mode.

Contribution

It provides the first detailed analysis of the finite-temperature lineshape and emergent resonances in the dynamical structure factor of the Heisenberg ladder.

Findings

Triplon mode broadens and becomes asymmetric with increasing temperature.

A temperature-induced resonance appears at low frequencies, similar to the Villain mode.

The dominant zero-temperature feature is a coherent triplon excitation.

Abstract

We determine the dynamical structure factor of the two-leg spin-1/2 Heisenberg ladder at low temperatures in the regime of strong rung coupling. The dominant feature at zero temperature is the coherent triplon mode. We show that the lineshape of this mode broadens in a non-symmetric way at finite temperatures and that the degree of asymmetry increases with temperature. We also show that at low frequencies a temperature induced resonance akin to the Villain mode in the spin-1/2 Heisenberg Ising chain emerges.