The dynamics of quantum criticality via Quantum Monte Carlo and holography

TL;DR

This paper combines quantum Monte Carlo simulations and holographic duality to analyze the real-time dynamics of quantum critical systems without quasiparticles, providing new quantitative insights into conductivity and spectral properties.

Contribution

It introduces a novel approach using holography to analytically continue Monte Carlo data, enabling detailed study of quantum critical dynamics without quasiparticles.

Findings

Universal low-frequency conductivity dependence on imaginary frequency and temperature

Quantitative predictions for frequency-dependent conductivity near criticality

Identification of quasinormal mode spectra in holographic models

Abstract

Understanding the real time dynamics of quantum systems without quasiparticles constitutes an important yet challenging problem. We study the superfluid-insulator quantum-critical point of bosons on a two-dimensional lattice, a system whose excitations cannot be described in a quasiparticle basis. We present detailed quantum Monte Carlo results for two separate lattice realizations: their low-frequency conductivities are found to have the same universal dependence on imaginary frequency and temperature. We then use the structure of the real time dynamics of conformal field theories described by the holographic gauge/gravity duality to make progress on the difficult problem of analytically continuing the Monte Carlo data to real time. Our method yields quantitative and experimentally testable results on the frequency-dependent conductivity near the quantum critical point, and on the spectrum of quasinormal modes in the vicinity of the superfluid-insulator quantum phase transition. Extensions to other observables and universality classes are discussed.