NEUTRAL · Neutral Quasi-Particles in Mesoscopic Physics

I propose to study ‘neutral excitations’ in 2d and 1d electronic systems. Such excitations, rarely studied, are unique since they are chargeless but may carry energy. Being byproducts of electron interaction, they come in a few flavors: (i) Downstream modes in composite edge channels of the integer quantum Hall effect (IQHE) regime; (ii) Upstream modes in the fractional quantum Hall effect (FQHE) regime; and (iii) Zero energy Majorana states (localized or propagating quasi-particles), in non-abelian FQHE states and in 1d topological P-wave superconductors. My main interests in neutral modes in the QHE regime are: (a) Their direct association with the nature of the wavefunction of the quantum state; (b) Being excited when a charge mode is being partitioned (say, by a quantum point contact), they may play a prime role in dephasing interference of quasi-particles due to the energy they rob (in the partitioning process). As for detecting Majorana quasi-particles, and aside from the exciting physics, their non-abelian nature makes them attractive as building blocks in ‘decoherence resistant’ systems. Based on our acquired abilities, such as material growth, processing techniques, and sensitive measurement techniques, I plan to perform experiments, which include: thorough studies of downstream and upstream neutral modes via shot noise and thermoelectric current measurements; proving (or disproving) their involvement in dephasing fractionally charged quasi-particles; growing and processing structures that harbor Majorana states (in 1d nano-wires and in 2d FQHE regime; and, possibly, eventually, manipulate Majorana states (by coupling and braiding). Experiments will employ, e.g., ultra-low temperatures, sensitive shot noise measurements, cross-correlation of current fluctuations, and interference of quasi-particles (charge and neutral) in novel interferometers.