Band-resolved imaging and nonlinear optical control of currents in topological materials

Introduction

Topological materials have captured the imagination of scientists with unique electronic dispersions and surface states. While their potential seems huge - from advanced photodetectors to spintronic devices - so far it has not come to fruition, despite two decades of research. In this proposal, my aim is to reveal and control light-matter interactions, electron populations, and currents in topological bands by combining two fields of research: topological materials and nonlinear optical coherent control.

Nonlinear Quantum Coherent Control

Nonlinear quantum coherent control was a major leap in ultrafast science, enabling optical control of chemical reactions and electronic processes in atoms and molecules on femtosecond time scales. In solid-state systems, despite some pioneering experiments, coherent control has not been widely used.

This is partially due to the complex band structures and partially because transport research has tended to be more easily applicable to the solid-state realm.

Promise of Topological Materials

Topological materials, however, are especially promising candidates for coherent control, because:

1. It has proven hard to access properties related to the topology in 3D materials via transport.
2. Topological bands are associated with unique optical selection rules.
3. As recently revealed, they exhibit fascinating nonlinear optical phenomena.

Project Goals

In this project, I will develop nonlinear coherent control of photocurrents in topological materials, thus building a bridge between nonlinear control and transport measurements of topological bands.

I will use time-resolved ARPES – a powerful tool providing band imaging out of equilibrium – to enable imaging of the photocurrents within the topological bands.

Expected Outcomes

PhotoTopoCurrent will establish a new research direction, which will:

• Provide a deep understanding of the unique optical couplings and nonlinear optical responses of topological electronic bands.
• Allow us to develop sophisticated optical schemes for tailored control.
• Finally, implement them in transport devices.