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arXiv:1901.04339 · Physical review. B./Physical review. B

Low-dimensional correlations under thermal fluctuations

Noam Kestin, Thierry Giamarchi

Published May 13, 2019• 3 citations
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Abstract

We study the correlation functions of quantum spin-$1/2$ two-leg ladders at finite temperature, under a magnetic field, in the gapless phase at various relevant temperatures $T\ensuremath{\ne}0$, momenta $q$, and frequencies $\ensuremath{\omega}$. We compute those quantities using the time-dependent density-matrix renormalization group (T-DMRG) in an optimal numerical scheme. We compare these correlations with the ones of dimerized quantum spin chains and simple spin chains, that we compute by a similar technique. We analyze the intermediate energy modes and show that the effect of temperature leads to the formation of an essentially dispersive mode corresponding to the propagation of a triplet mode in an incoherent background, with a dispersion quite different from the one occurring at very low temperatures. We compare the low-energy part of the spectrum with the predictions of the Tomonaga-Luttinger liquid field theory at finite temperature. We show that the field theory describes in a remarkably robust way the low-energy correlations for frequencies or temperatures up to the natural cutoff (the effective dispersion) of the system. We discuss how our results could be tested in, e.g., neutron-scattering experiments.

DOI
10.1103/physrevb.99.195121

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