Jonathan Baugh, Institute for Quantum Computing
Abstract:
Nanotechnology is continually providing new materials to explore
for use in future classical and quantum devices. We have recently
investigated low temperature electronic transport in various device
configurations based on InAs nanowires. In a simple field-effect
transistor geometry, magnetoconductance experiments on core-shell
nanowires reveal phase coherent electronic states. In particular,
oscillations in axial-field magnetoconductance with periodicity
corresponding to the flux quantum are a signature of coherent 'ring'
states around the wire circumference, owing to a surface accumulation
layer of electrons [1]. These results suggest a high degree of structural
order, i.e. that properly tailored nanowires can serve as a reasonably
clean system for a variety of quantum transport experiments. Secondly,
motivated by the recent search for topological states in
semiconductor-superconductor heterostructures, we have investigated a
nanowire in the quasi-ballistic regime contacted with a type-II
superconductor, Niobium. A supercurrent is observed in this junction below
a critical current of up to 40 nA; the critical current varies with local
gating in proportion to the normal state conductance. Detailed analysis of
a wide range of data from this device reveals certain features that are
expected for SNS junctions, and some that are as yet puzzling, and may be
related to the quasi-1D nature of the nanowire. I will discuss these
results in the light of potential quantum device applications.
[1] http://lanl.arxiv.org/abs/1305.5552