Physics Seminar: Graphene

Thursday, February 21, 2019 The event started -94 days ago

10:50 AM11:50 AM

Optics Building

Room 234

Spin Resonance and Domain Confined Currents in Graphene

Dr Ramesh Mani (Georgia State)

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).


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