Electrically-Tunable Light-Matter Interactions in Quantum Materials

Citation

Whitney, William Schuyler (2019) Electrically-Tunable Light-Matter Interactions in Quantum Materials. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/KKB7-KN62. https://resolver.caltech.edu/CaltechTHESIS:05252019-154108242

Abstract

Dynamic control of the flow of light at the nanoscale is critical for next-generation optoelectronic devices that will enable the technologies of the future. Ultra-thin, layered materials are promising building blocks for this functionality, as they are easily fabricated into atom-scale structures, and their optical properties change dramatically under applied electric fields. Many of these material systems, like topological insulators – a subset of layered materials that host spin-polarized surface states, promise more exotic functionality as well. The emerging field of nanophotonics in quantum materials is a route not only to an improved material platform for optoelectronics, but also to new physics, and the potential new device paradigms that follow.

In this work we describe investigations of electrically-tunable light-matter interactions in two different layered materials: few-layer black phosphorus, and bismuth antimony telluride. In few-layer black phosphorus, we demonstrate several in-plane anisotropic optoelectronic phenomena, including Pauli-blocking of intersubband optical transitions under carrier injection, a quantum-confined Stark effect, and a change of quantum well selection rules under applied electric field. We further describe how these optoelectronic phenomena drive anisotropic birefringence and dichroism in few-layer black phosphorus. Lastly, we present theory describing amplitude, phase and polarization control in a black phosphorus integrated microcavity device, with applications that include metasurface beam-steering and more.

We next present experiments demonstrating field-effect control of optical transitions in bismuth antimony telluride. These measurements evidence the merits of topological insulators as optoelectronic materials, and highlight a pathway towards future exploration of spin-plasmon excitations in bismuth antimony telluride.

Lastly, we present a summary of pending work, including initial results of an ongoing study of plasmon excitations in few-layer black phosphorus, and a perspective on next steps for both these projects and nanophotonics in quantum materials at large.

Thesis Files