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.

arXiv comment5 pages + 7 pages supplement, 10 figures included. Final version as published

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Cited by in corpus (8)

• Inhomogeneous mean-field approach to collective excitations in disordered interacting bosons
• Localization of the Higgs mode at the superfluid-Mott glass transition
• Dynamic structure factor of Heisenberg bilayer dimer phases in the presence of quenched disorder and frustration
• Green's functions on a renormalized lattice: An improved method for the integer quantum Hall transition
• Scalar susceptibility of a diluted classical XY model
• Critical Behavior and Collective Modes at the Superfluid Transition in Amorphous Systems
• Quantum Spin Liquids Stabilized by Disorder in Non-Kramers Pyrochlores
• Amplitude mode at the superfluid-insulator transition on a random lattice