The role of molecular beam epitaxy in fundamental physics through an example: assessing the impact of disorder on the v=5/2 fractional quantum Hall effect – Mike Manfra

Date: Fri. March 30th, 2012, 11:30 am-12:30 pm
Location: Rockefeller 306

Thirty years after its initial discovery, the fractional quantum Hall effect continues to challenge our understanding of electronic correlations in low dimensions. Throughout this history advances in molecular beam epitaxy (MBE) have played an important role. Presently, the fragile v=5/2 fractional quantum Hall state is the subject of intense scrutiny. It is theoretically conjectured that the v=5/2 state is described by the Moore-Read Pfaffian wavefunction, possessing excitations obeying non-Abelian braiding statistics. If experimentally confirmed, excitations with non-Abelian braiding statistics may provide a platform for proposed schemes of topologically-protected quantum computing. While there are many aspects to the physics at v=5/2, the role of disorder remains still poorly understood. The measured excitation gap at v=5/2 remains rather small, ~0.5K at best. This limit does not yet appear fundamental as general improvements in sample quality continue to result in larger experimental gaps. However we lack a detailed understanding of what types of disorder are most detrimental to the v=5/2 state. Our ongoing work at Purdue focuses on trying to understand the impact of disorder, ever present in real samples, on the v=5/2 state. I will describe our attempts to isolate the most important types of disorder through targeted MBE growth studies.