Charge carriers in materials are often described as particles similar to free electrons but characterized by effective quantities such as an effective mass. However, electrons in topological materials defy this description; they acquire an additional quantum mechanical property - Berry curvature - that radically alters their dynamics.
I will discuss how exploiting Berry curvature in recently discovered two-dimensional heterostructures, such as graphene on hexagonal-boron-nitride (G/h-BN), grants control over the valley index - an internal quantum degree of freedom akin to spin. This strikingly manifests in low-dissipation transverse valley currents that can be decoupled from charge. I will discuss (i) recent measurements of topological valley currents in G/hBN devices, (ii) how dissipation can be further suppressed using valley waveguides that allow valley currents to persist even in an insulating bulk, and (iii) how Berry curvature can alter opto-electronic properties such as a chiral flow of plasmons without magnetic field. These provide a new toolbox to engineer electronic and optoelectronic action directly into the electron wavefunction.
Justin Song is a Burke fellow and Sherman Fairchild scholar of physics at Caltech. He received a BSc in physics from Imperial College London (2007), an AM in physics from Harvard (2011), and a Ph.D. in applied physics at Harvard (2014).
Justin's research interests lie at the interface between engineering and solid-state physics, and include novel charge/valley/spin/energy transport, opto-electronics, topological materials, and 2D layered heterostructures. He is the recipient of the Caltech prize fellowship in physics, the APS Ovshinsky Award, and a National Science Scholarship.