Divergent Nonlinear Response from Quasiparticle Interactions

We demonstrate that nonlinear response functions in many-body systems carry a sharp signature of interactions between gapped low-energy quasiparticles. Such interactions are challenging to deduce from linear response measurements. The signature takes the form of a divergent-in-time contribution to t...

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Bibliographic Details
Published in:Physical review letters 2023-12, Vol.131 (25), p.256505-256505, Article 256505
Main Authors: Fava, Michele, Gopalakrishnan, Sarang, Vasseur, Romain, Essler, Fabian, Parameswaran, S A
Format: Article
Language:English
Subjects:
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Quantum many-body systems
Third order nonlinear optical processes
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Summary:We demonstrate that nonlinear response functions in many-body systems carry a sharp signature of interactions between gapped low-energy quasiparticles. Such interactions are challenging to deduce from linear response measurements. The signature takes the form of a divergent-in-time contribution to the response-linear in time in the case when quasiparticles propagate ballistically-that is absent for free bosonic excitations. We give a physically transparent semiclassical picture of this singular behavior. While the semiclassical picture applies to a broad class of systems we benchmark it in two simple models: in the Ising chain using a form-factor expansion, and in a nonintegrable model-the spin-1 Affleck-Kennedy-Lieb-Tasaki chain-using time-dependent density matrix renormalization group simulations. We comment on extensions of these results to finite temperatures.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.131.256505