Techniques to measure quantum criticality in cold atoms

TL;DR

This paper discusses methods to extract universal scaling functions from cold atom experiments to better understand quantum criticality, which is essential for insights into high-temperature superconductors, heavy fermion systems, and graphene.

Contribution

It introduces techniques to measure quantum critical scaling functions using cold atom experiments, bridging experimental data with theoretical models.

Findings

Universal scaling functions can be extracted from atomic density profiles.

Experimental methods can resolve the Mott-Metal crossover.

Insights into quantum critical dynamics relevant to high-temperature superconductors.

Abstract

Attempts to understand zero temperature phase transitions have forced physicists to consider a regime where the standard paradigms of condensed matter physics break down [1-4]. These quantum critical systems lack a simple description in terms of weakly interacting quasiparticles, but over the past 20 years physicists have gained deep insights into their properties. Most dramatically, theory predicts that universal scaling relationships describe their finite temperature thermodynamics up to remarkably high temperatures. Unfortunately, these universal functions are hard to calculate: for example there are no reliable general techniques [4,5] to calculate the scaling functions for dynamics. Viewing a cold atom experiment as a quantum simulator [6], we show how to extract universal scaling functions from (non-universal) atomic density profiles or spectroscopic measurements. Such experiments can resolve important open questions about the Mott-Metal crossover [7,8] and the dynamics of the finite density O(2) rotor model [1,9], with direct impact on theories of, for example, high temperature superconducting cuprates [10,11], heavy fermion materials [12], and graphene [13].