CAREER: Crystalizing electrons in coupled atomically thin semiconductors

University Of Maryland, College Park, College Park MD

Investigators

Abstract

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Nontechnical Description: The most commonly known phases of matter are gas, liquid, and solid. Just as vapor can condense into a crystalline solid, electrons in a semiconductor can self-arrange into a periodic pattern, a crystal, at low temperatures. Although predicted more than eight decades ago, such crystallization of electrons is challenging to realize and observe. This project investigates the formation and melting of electron solids in two-dimensional (2D) materials that are only a few atoms thick. Such 2D materials can be stacked together in different combinations and orientations, which strongly influences how electrons behave. The project studies ways to promote electron crystallization by controlling the stacking of coupled 2D semiconductors. The research also develops methods to controllably melt electron crystals using quantum fluctuations, paving the way for new devices for quantum computing and communications. An integral part of the project is to provide high-school, undergraduate, and graduate students with hands-on research opportunities in leading-edge materials and optics labs. In collaboration with local high schools and national non-profit organizations, the project also establishes internship and mentorship programs targeting underrepresented groups in science and engineering. This project is jointly funded by the Electronic and Photonic Materials (EPM) and the Condensed Matter Physics (CMP) programs of the Division of Materials Research (DMR). Technical Description: The study of Wigner crystals is critical for understanding how the competition between electron correlation and quantum fluctuations gives rise to exotic properties in correlated electron materials. Recent experiments reported the formation of bilayer Wigner crystals with significantly enhanced stability when two transition metal dichalcogenide monolayers are placed close to each other. This project aims to establish new systems and methods to interrogate the quantum phase transitions of Wigner crystals to enable a platform for quantum electronic and optoelectronic devices. By fabricating coupled bilayer heterostructures based on transition metal dichalcogenides, the project investigates how the atomic structures of the materials influence the stability of the electron crystals. Central to this effort is developing quantitative approaches to investigate the lattice structures and dynamics in the Wigner crystal phase. By exploiting the electrical control of quantum phase transitions, the project explores novel correlated phases such as electron glasses. The research activities elucidate phase competition in many-body quantum systems and paves the way for next-generation electronic and optical devices. A particular focus of the project is to broaden the participants from underrepresented groups by collaborating with local high schools, universities, as well as national non-profit organizations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.