SKM 2021 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 9: Poster Session: Correlated Electrons
TT 9.32: Poster
Tuesday, September 28, 2021, 13:30–16:00, P
Inhomogeneous mean-field approach to collective excitations near the superfluid–Mott glass transition — •Martin Puschmann1,2, João C. Getelina1,3, José A. Hoyos3, and Thomas Vojta1 — 1Department of Physics, Missouri University of Science and Technology, Rolla, Missouri, 65409, USA — 2Institute of Theoretical Physics, University of Regensburg, D-93040, Regensburg, Germany — 3Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, São Carlos, São Paulo, 13560-970, Brazil
We develop an inhomogeneous quantum mean-field approach to the behavior of collective excitations across the superfluid–Mott glass transition in two dimensions, complementing recent quantum Monte Carlo simulations [1,2]. In quadratic approximation, the Goldstone (phase) and Higgs (amplitude) modes completely decouple. Each is described by a disordered Bogoliubov Hamiltonian which can be solved by an inhomogeneous multi-mode Bogoliubov transformation. We find that the Higgs mode is spatially localized in both phases. The corresponding scalar spectral function shows a broad peak that is noncritical in the sense that its peak frequency does not soften but remains nonzero across the quantum phase transition. In contrast, the lowest-energy Goldstone mode delocalizes in the superfluid phase, leading to a zero-frequency spectral peak. We compare these findings to both the results of the quantum Monte Carlo simulations and the general knowledge on localization of bosonic excitations. We also show first results for three-dimensional systems.
[1] M. Puschmann et al., Phys. Rev. Lett. 125 (2020), 027002
[2] M. Puschmann et al., Ann. Phys. (2021), 168526