Spectral damping without quasiparticle decay: The dynamic structure factor of two-dimensional quantum Heisenberg antiferromagnets

TL;DR

This paper analytically solves the dynamic structure factor of 2D quantum Heisenberg antiferromagnets at finite temperature, revealing broad spectra and multi-scale physics despite long quasiparticle lifetimes.

Contribution

It introduces a novel quantum-classical duality approach to analytically compute dynamic correlations, uncovering multi-scale phenomena that challenge existing theories.

Findings

Broad frequency spectrum observed despite long quasiparticle lifetime

Excellent agreement between Monte Carlo simulations and the analytical theory

Reveals multi-scale physics involving classical radiation fields

Abstract

Two-dimensional Heisenberg antiferromagnets play a central role in quantum magnetism, yet the nature of dynamic correlations in these systems at finite temperature has remained poorly understood for decades. We solve this long-standing problem by using a novel quantum-classical duality to calculate the dynamic structure factor analytically and, paradoxically, find a broad frequency spectrum despite the very long quasiparticle lifetime. The solution reveals new multi-scale physics whereby an external probe creates a classical radiation field containing infinitely-many quanta. Crucially, it is the multi-scale nature of this phenomenon which prevents a conventional renormalization group approach. We also challenge the common wisdom on static correlations and perform Monte Carlo simulations which demonstrate excellent agreement with our theory.