Imaging The Topological Defects of Light-Induced Phases in Quantum Materials

Introduction

Quantum materials host many exotic and useful phases, and harnessing these states has spurred tremendous research effort. However, the full potential of quantum materials lies in the rich landscape of higher-energy hidden phases, those which are not thermally accessible. Ultrafast laser excitation has recently emerged as a way to access these hidden phases, leading to the idea of re-writing material properties “on demand”, but these states usually only survive for hundreds of picoseconds. Thus, a key outstanding question remains: how can we stabilize light-induced phases?

Topological Defects

One key mechanism which can stabilize a phase is topology. The ultrafast phase transitions induced by femtosecond laser pulses naturally lead to the generation of topological defects. These defects, which can only relax after propagating until they encounter another topological defect, could either offer a route to stabilizing light-induced phases or impede their formation. They have been invoked in both contexts to explain many observations.

However, actually imaging these nanometer scale defects on the femtosecond to nanosecond timescales required for light-induced phases has not been possible, and so the role of topological defects in light-induced phases remains unclear.

Project Overview

In KnotSeen, I will perform the first real space imaging of topological defects in light-induced phases using coherent XUV imaging methods. These methods provide the necessary spatial, temporal, and spectral resolution to map topological defects at the nanoscale and out of equilibrium.

Research Focus

I will map the creation, propagation, and destruction of topological defects in two important cases:

1. Quenched superconductivity in the cuprates
2. Light-induced phases in the manganites

A novel data analysis approach will be used to distinguish repeatable from stochastic dynamics at the nanoscale.

Expected Outcomes

KnotSeen will reveal the mechanisms by which topological defects control light-induced phases, enabling new tools to stabilize and selectively control them.