Department of Physics

Indian Institute Of Technology Madras , Chennai

A magneto-transport study of graphene

Speaker : Dr. Ramesh J. Mani, Dept. of Physics & Astronomy, Georgia State University, Atlanta U.S.A.


Abstract :

Graphene is an interesting electronic material because (a) it exhibits a linear relativistic dispersion relation along with carrier type conversion without crossing a bandgap, (b) it shows a high carrier mobility at room temperature, and (c) it promises long spin lifetimes. In order to address questions relating to these areas, we have examined equilibrium carrier transport in the vicinity of the neutrality point in CVD graphene in addition to quasi non-equilibrium microwave photo-excited transport in epitaxial graphene. The photo-excited transport study in epitaxial graphene demonstrated the possibility of the electrical detection, and microwave characterization of spin. Experiment indicated a strong non-resonant microwave induced change in the diagonal resistance, indicative of a carrier heating effect. In addition, a pair of resonant responses consistent with spin resonance and pseudo-spin-split spin-resonance were observed. These resonances were followed with microwave frequency and the results were fit to extract the g-factor, g ~ 1.93, the zero-magnetic field pseudo-spin splitting, ~ 44 micro-eV, and the spin relaxation time, ~ 60 ps.[1] The equilibrium transport study in CVD graphene served to examine Hall effect compensation and a nearly quantized residual resistivity over the p <-> n transition about the nominal Dirac point. The observed characteristics were reproduced in a model with a parabolic distribution of neutrality potentials, VN, and simultaneous electron- and hole- conduction. The results suggested that, about the gate-induced n <-> p transition, charge transport is characterized by domain confined bipolar currents, with oppositely oriented Hall electric fields within the electron and hole streams, which leads to compensation in the global Hall effect and the observed residual resistivity. [2] [1] R. G. Mani, J. Hankinson, C. Berger, and W. A. de Heer, Nat. Comm. 3, 996 (2012). [2] R. G. Mani, Appl. Phys. Lett. 108, 033507 (2016). संक्षिप्त जीवनी / Brief Biography : 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), California. 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.

Key Speaker Dr. Ramesh J. Mani, Dept. of Physics & Astronomy, Georgia State University, Atlanta U.S.A.
Guests None
Place Conference Room
Start Time 11:00 AM
Finish Time 11:00 AM
External Link None