Paola Ruggiero, Pasquale Calabrese, Thierry Giamarchi, Laura Foini
SciPost Phys. 13, 111 (2022) ·
published 18 November 2022

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The study of nonequilibrium dynamics of manybody systems after a quantum quench received a considerable boost and a deep theoretical understanding from the path integral formulation in imaginary time. However, the celebrated problem of a quench in the Luttinger parameter of a one dimensional quantum critical system (massless quench) has so far only been solved in the realtime Heisenberg picture. In order to bridge this theoretical gap and to understand on the same ground massive and massless quenches, we study the problem of a gaussian field characterized by a coupling parameter $K$ within a strip and a different one $K_0$ in the remaining two semiinfinite planes. We give a fully analytical solution using the electrostatic analogy with the problem of a dielectric material within a strip surrounded by an infinite medium of different dielectric constant, and exploiting the method of charge images. After analytic continuation, this solution allows us to obtain all the correlation functions after the quench within a path integral approach in imaginary time, thus recovering and generalizing the results in real time. Furthermore, this imaginarytime approach establishes a remarkable connection between the quench and the famous problem of the conductivity of a TomonagaLuttinger liquid coupled to two semiinfinite leads: the two are in fact related by a rotation of the spacetime coordinates.
Paola Ruggiero, Pasquale Calabrese, Laura Foini, Thierry Giamarchi
SciPost Phys. 11, 055 (2021) ·
published 13 September 2021

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We study the quantum quench in two coupled TomonagaLuttinger Liquids (TLLs), from the offcritical to the critical regime, relying on the conformal field theory approach and the known solutions for single TLLs. We consider a squeezed form of the initial state, whose low energy limit is fixed in a way to describe a massive and a massless mode, and we encode the nonequilibrium dynamics in a proper rescaling of the time. In this way, we compute several correlation functions, which at leading order factorize into multipoint functions evaluated at different times for the two modes. Depending on the observable, the contribution from the massive or from the massless mode can be the dominant one, giving rise to exponential or powerlaw decay in time, respectively. Our results find a direct application in all the quench problems where, in the scaling limit, there are two independent massless fields: these include the Hubbard model, the GaudinYang gas, and tunnelcoupled tubes in cold atoms experiments.
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