Designer electronic states in van der Waals heterostructures

Who: Brian LeRoy, Arizona
Monday, April 11, 2022 - 3:30pm

A CMU/Pitt Colloquium

Abstract: The ability to create arbitrary stacking configurations of layered two-dimensional materials has opened the way to the creation of designer band structures.  Twisted bilayer graphene and graphene on hexagonal boron nitride are two of the simplest examples of such a van der Waals heterostructure where the electronic properties of the composite material can be fundamentally different from either individual material.   These van der Waals heterostructures can be formed using a wide variety of layered materials including transition metal dichalcogenides, graphene and topological insulators.  The lattice mismatch and twist angle between layers in the heterostructure produces a moiré pattern which affects its electronic properties.  This talk will mostly focus on creating novel electronic states by controlling the twist angle and breaking inversion symmetry.  In small twist angle bilayer graphene or transition metal dichalcogenides, the long-wavelength moiré pattern leads to the creation of flat bands and a wide range of correlated electronic states.  In this talk, I will discuss our fabrication of these heterostructures and measurements using scanning probe microscopy.