Seminars
Seminars occur on Wednesday afternoons in ISB 130 and run between 12:00-1:00 PM Pacific with a hybrid option over Zoom unless otherwise posted. To join the mailing list, please contact Prof. Ken Wharton at kenneth.wharton@sjsu.edu with the words "Seminars and Events" included in the subject heading.
This Week
Simultaneous Strain and Gate Tunability of Moiré Heterostructure Devices
Jordan Fonseca
University of Washington
Wednesday, 5/1/2024, 12:00-1:00pm Pacific
Abstract: Moiré heterostructures of 2D materials have served as a platform for studying and
engineering a wide variety of correlated phenomena and many body physics. The atomic
thickness of two-dimensional materials and the large effective lattice constant of
moiré superlattices make electrostatic gating a particularly effective way to tune
carrier density and thereby explore a rich phase diagram of correlated effects. Independently,
two dimensional materials exhibit unusually high elasticity and can sustain significant
uniaxial strain before yielding. Uniaxial strain breaks rotational symmetry and changes
interatomic spacing, altering many material properties in the process. An outstanding
challenge, however, is simultaneously and independently tuning uniaxial strain and
electrostatic gating in-situ at cryogenic temperatures. In this talk, I will discuss
our work to leverage novel approaches for efficient strain transfer to the moiré heterostructure
in gateable van der Waals devices. I will show how the ability to traverse the strain-gating
phase space for a high-quality transition metal dichalcogenide moiré heterostructure
enables exploration of novel features in the photoluminescence spectra and discuss
their origin in the underlying optoelectronic properties of this rich material system.
Bio: Jordan Fonseca is a graduate student researcher in the Department of Physics at the University of Washington. He attended undergrad at the University of Puget Sound, where he majored in Physics and Math and was involved in the Honors program and the campus writing and tutoring center. While at Puget Sound, he did summer research at Los Alamos National Laboratory, built a time-resolved photoluminescence experiment at Puget Sound, and spent an REU at the University of Washington working with his now-PhD advisor, Professor Xiaodong Xu. As a graduate student at the University of Washington, he focuses on optical and atomic force microscope measurements of 2D materials and their device heterostructures. His research projects have spanned ultrafast measurements of topological insulators, imprinting moiré superlattice potentials on adjacent target materials, and developing techniques to integrate uniaxial strain and electrostatic gating on moiré heterostructure devices. While at the University of Washington, Jordan has been an active member of the Physics Graduate Student Council, serving both on departmental committees and as the group spokesperson for two years. Jordan has also led multiple orientation hikes for new students, mentored REU students, served on the leadership team for an undergraduate physics mentoring program, and volunteered on the organizing committee for the 2023 Conference for Undergraduate Women in Physics.
