Phasonic Spectroscopy of a Quantum Gas in a Quasicrystalline Lattice

TL;DR

This paper demonstrates phasonic spectroscopy in a quantum gas within a 1D quasicrystalline optical lattice, revealing unique high-harmonic responses and multifractal spectra that advance understanding of quasicrystal properties.

Contribution

It introduces a method to dynamically probe phasonic degrees of freedom in a quantum gas, enabling direct observation of quasiperiodicity and multifractal energy spectra.

Findings

Observation of a nonperturbative high-harmonic plateau under strong phasonic driving

Identification of spectroscopic signatures of quasiperiodicity and interactions

Mapping of a multifractal energy spectrum and potential imaging of the Hofstadter butterfly

Abstract

Phasonic degrees of freedom are unique to quasiperiodic structures, and play a central role in poorly-understood properties of quasicrystals from excitation spectra to wavefunction statistics to electronic transport. However, phasons are challenging to access dynamically in the solid state due to their complex long-range character and the effects of disorder and strain. We report phasonic spectroscopy of a quantum gas in a one-dimensional quasicrystalline optical lattice. We observe that strong phasonic driving produces a nonperturbative high-harmonic plateau strikingly different from the effects of standard dipolar driving. Tuning the potential from crystalline to quasicrystalline, we identify spectroscopic signatures of quasiperiodicity and interactions and map the emergence of a multifractal energy spectrum, opening a path to direct imaging of the Hofstadter butterfly.