Single quasiparticle pumping in the integer and fractional quantum Hall regime

This experimental PhD project will develop semiconductor nanodevices and cryogenic measurement technologies for controlled transfer of single quasiparticles (electrons or fractionally-charged quasiparticles). At NPL, the student will investigate the visibility of Aharonov-Bohm oscillations of quantum antidots in the integer and fractional quantum Hall regimes. This will test the capability of NPL’s cryogenic measurement facility for interferometer experiments. After optimising the device operation condition, the current quantisation by periodic transfer of single quasiparticles will be investigated. The non-Abelian¹ fractional states at filling factors of nu=5/2 and 12/5 are of particular interest as a possible route to topological quantum computing¹; the exact nature of the ground states is still not fully understood and measurements at ultra-low temperatures will be pursued at Royal Holloway. A set of bound states is formed around a submicron antidot when a split-gate device with an additional surface gate at its centre is subjected to a strong magnetic field. The quantum Hall edge channels in the left and right leads allow electrons to tunnel through the states in the antidot, behaviour that is well understood¹ in the integer quantum Hall regime. How similar devices behave in the fractional quantum Hall regime, at higher magnetic fields and mK electron temperatures³, when driven at high frequencies is the goal of this project. Skills that could be acquired during the PhD project: nanofabrication, low temperature physics, RF techniques, and many-body quantum physics.