Microwave photoexcited transport studies in the fractional quantum Hall regime
ABSTRACT :
A metallic state with a vanishing activation gap, at a filling factor 8/5 in the untilted
specimen with n = 2 × 10^11cm^(−2) , and at filling factor 4/3 at n = 1.2 × 10^11cm^(−2) a t
a tilt angle of 66 degrees between the magnetic field and the plane of the specimen, is
examined through a microwave photo-excited transport study of the GaAs/AlGaAs 2
dimensional electron system (2DES). The results presented here suggest, remarkably, that
at the possible degeneracy point of states with different spin polarization, where the 8/5 or
4/3 FQHE vanish, there occurs a peculiar marginal metallic state that differs qualitatively
from a quantum Hall insulating state and the usual quantum Hall metallic state. Such a
marginal metallic state occurs most prominently at filling factor of 8/5 , and at filling factor
of 4/3 under tilt as mentioned above, between span between filling factors 1 and 2, that
also includes the 3/2 state, which appears perceptibly gapped in the first instance.
ABOUT THE SPEAKER:
Prof. Ramesh Mani is an Indian-born American physicist who obtained his BS, MS, and
Ph.D. at the University of Maryland, College Park, MD in the USA. After the time at the
University of Maryland, he worked as a scientist at the Max-Planck-Institute for Solid State
Physics in Stuttgart, Germany. He returned to the USA with a position at the University of
California at Santa Barbara (UCSB), Cali fornia. After a brief stay at UCSB, he moved to
Harvard University as a senior research associate in Dean Venky Narayanamurti's group.
In 2006, he moved to Georgia State University where he is now Professor of Physics &
Astronomy. At Georgia State University, he has set up a large laboratory for materials
preparation, device fabrication by lithography, and low temperature, high magnetic field
magneto-transport studies of low dimensional systems based on GaAs/AlGaAs
heterostructures, graphene, and other modern atomic layer 2D systems.