Michelle Tomczyk PhD Defense

July 12, 2017 - 10:00am to 12:00pm

Title: Electronic Interactions in Complex-Oxide Nanodevices

Abstract: Strontium titanate (SrTiO3) is known as a superconducting semiconductor and possesses characteristics suggesting an unconventional pairing mechanism; however, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. SrTiO3-based interfaces can provide new clues about electronic interactions leading to pairing. In particular, the electronic system at the interface of LaAlO3 and SrTiO3 hosts a broad array of emergent phenomena, including superconductivity, spin-orbit coupling, and magnetism, providing a tantalizing platform to study electronic interactions.

In this dissertation, nanodevices with well-characterized quantum behavior are used as probes of the interfacial electronic system. These devices enable coherent single-electron and single-subband resolution of electronic states, which can elucidate the microscopic details of electronic interactions. Tunneling behavior through nanowire quantum dots reveals the existence of electron pairs far outside the superconducting regime. While this suggests strong attractive interactions, Andreev transport at higher gate voltages indicates a gate-tunable sign change of electron-electron interactions. Ballistic transport over micrometer distances produces quantum interference oscillations in nanowire cavities, and also leads to conductance plateaus at various integer values of e2/h in electron waveguide devices. Evolution of the plateaus in an applied magnetic field reveals details of the strength and variation of the electron pairing, and other related physical properties such as the g-tensor, scattering length and superconducting gap. These results provide guidance to theoretical predictions of the microscopic origins of the electron pairing interactions.

Location and Address

321 Allen Hall