Collective Modes at a Disordered Quantum Phase Transition
Abstract
We study the collective excitations, i.e., the Goldstone (phase) mode and the Higgs (amplitude) mode, near the superfluid-Mott glass quantum phase transition in a two-dimensional system of disordered bosons. Using Monte Carlo simulations as well as an inhomogeneous quantum mean-field theory with Gaussian fluctuations, we show that the Higgs mode is strongly localized for all energies, leading to a noncritical scalar response. In contrast, the lowest-energy Goldstone mode undergoes a striking delocalization transition as the system enters the superfluid phase. We discuss the generality of these findings and experimental consequences, and we point out potential relations to many-body localization.
- Publication:
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Physical Review Letters
- Pub Date:
- July 2020
- DOI:
- 10.1103/PhysRevLett.125.027002
- arXiv:
- arXiv:1911.04452
- Bibcode:
- 2020PhRvL.125b7002P
- Keywords:
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- Condensed Matter - Disordered Systems and Neural Networks;
- Condensed Matter - Quantum Gases;
- Condensed Matter - Strongly Correlated Electrons
- E-Print:
- 5 pages + 7 pages supplement, 10 figures included. Final version as published