Department of Applied Physics and Materials Science - Materials Science

Materials Science Research Lecture

Thursday February 7, 2019 10:00 AM

Quantum phase transitions in ZnO two-dimensional electron systems

Speaker: Joseph Falson, Max Planck Institute for Solid State Research
Location: Noyes 153 (J. Holmes Sturdivant Lecture Hall)

Abstract: Amongst a wave of new low dimensional materials, ZnO-based heterostructures have emerged to display high electron mobility concomitant to strong correlation effects. In this presentation, I will explore the molecular beam epitaxy growth techniques of MgZnO/ZnO heterostructures which exhibit electron mobilities in excess of 106 cm2/Vs, representing crystallinity comparable to traditional semiconductor systems. Owing to the large effective mass and small dielectric constant of this system, the coulomb interaction energy dominates the kinetic energy of carriers, culminating in the formation of a fantastic array of correlated electronic ground states at low temperatures.  Within a magnetic field, I will demonstrate tunability between fractional quantum Hall, compressible metallic, and anisotropic nematic phases by shifting the spin and orbital polarization of carriers occupying discretized Landau levels. Turning off the magnetic field, I will explore the breakdown of the two-dimensional Fermi liquid as the ratio of coulomb to kinetic energies is tuned. In the strongly interacting limit, a divergent spin susceptibility and a non-linear current-voltage response emerge as the fingerprints of a Stoner ferromagnet induced metal-insulator transition in two-dimensions.

More About the Speaker: Joseph Falson is a Nobel Laureate Fellowship postdoctoral researcher at the Max Planck Institute for Solid State Research in Stuttgart, Germany. His research focuses on the epitaxy of high mobility oxide two-dimensional electron systems and the study of their electronic properties at low temperature and high magnetic field. He obtained his Ph.D. from the University of Tokyo and B.Sc. from the University of New South Wales.

Series Materials Research Lecture Series

Contact: Jennifer Blankenship at 626-395-8124 jennifer@caltech.edu