Controlling symmetry and localization with an artificial gauge field in a disordered quantum system

Clément Hainaut,Jean-François Clément,Gabriel Lemarié,Radu Chicireanu,Nicolas Cherroret,Pascal Szriftgiser,Isam Manai,Dominique Delande,Jean Claude Garreau

doi:10.1038/s41467-018-03481-9

Abstract

Anderson localization, the absence of diffusion in disordered media, draws its origins from the destructive interference between multiple scattering paths. The localization properties of disordered systems are expected to be dramatically sensitive to their symmetries. So far, this question has been little explored experimentally. Here we investigate the realization of an artificial gauge field in a synthetic (temporal) dimension of a disordered, periodically driven quantum system. Tuning the strength of this gauge field allows us to control the parity–time symmetry properties of the system, which we probe through the experimental observation of three symmetry-sensitive signatures of localization. The first two are the coherent backscattering, marker of weak localization, and the recently predicted coherent forward scattering, genuine interferential signature of Anderson localization. The third is the direct measurement of the β(g) scaling function in two different symmetry classes, allowing to demonstrate its universality and the one-parameter scaling hypothesis.

Highlights

Anderson localization, the absence of diffusion in disordered media, draws its origins from the destructive interference between multiple scattering paths
When KðtÞ is temporally modulated at a period 2π/ω2 incommensurate with the kick period, it has been shown[9,13,14] that the temporal modulation can be taken into account by adding an effective spatial coordinate x2 = ω2t + φ along a synthetic dimension labeled “2” (“1” refers to the physical dimension along which all measurements are performed)
We experimentally studied the Coherent backscattering (CBS) and coherent forward scattering (CFS) effects by using a thermal, ultra-cold cloud of Cs atoms kicked by a series of short pulses of a far-detuned standing wave created by a pair of counter-propagating laser beams

Summary

Introduction

The absence of diffusion in disordered media, draws its origins from the destructive interference between multiple scattering paths. We exploit the simplicity and flexibility of driven cold-atom systems to generate such an artificial gauge field For this purpose, we build on the well-known atomic kicked rotor[7], a paradigm of both classical and quantum Hamiltonian chaos, which can be mapped onto an Anderson-like Hamiltonian in any dimension[8,9]. The accumulated phase of a quantum particle along a closed multiple-scattering path is independent of the sense in which the loop is traveled when PT-invariance holds (defining the so-called orthogonal symmetry class), but not when it is broken (defining, for spinless systems, the unitary class), an effect that strongly affects quantum interference in localization phenomena This allows us to directly observe the impact of this symmetry changing on interference signatures of localization in disordered media, and to study the universal transport properties in the two symmetry classes

Methods

Results

Conclusion