Departmental Oral Examination (Thesis Title: “Local Probe of Electronic States In High Mobility Quantum Hall Samples”)

Speaker: 
MOHAMMAD SAMANI
Event Date and Time: 
Tue, 2017-02-28 15:15 - 17:45
Location: 
Henn 309
Local Contact: 
Physics and Astronomy, UBC
Intended Audience: 
Public

Abstract:
The discovery of the integer quantum Hall effect (IQHE) and the fractional quantum Hall effect (FQHE) in a 2-dimensional electron gas (2 DEG) have created a new and rich field in condensed matter physics in low dimensions. Almost 35 years after these discoveries, there are still several unanswered questions regarding the nature of various electronic phases that are formed in these systems. The 2 DEG formed in ultra-high mobility quantum well (QW) samples in large magnetic fields and millikelvin temperatures are studied in this thesis. We developed a reproducible recipe for enhancing the quality of the very fragile FQHE states reliably, which can be used to reset a electrically shocked sample in-situ at low temperatures.

We investigated theories that predict a new state of matter, the non-Abelian state, that follows neither Fermionic nor Bosonic quantum statistics. Non-Abelian quasi-particles are expected to form as collective excitations in the quantum Hall regime. We used a single-electron transistor (SET), an ultra sensitive electrometer, and we developed a fast heating technique using on-chip heaters for this investigation.

We also used the SET to study the nature of localization of electrons in the bulk of the sample when the system is in incompressible states near the centres of IQHE plateaus.

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