Condensed Matter Seminar Series

Spin and charge transport in low-dimensional systems

Xincheng Xie

Oklahoma State University

Thursday March 3, 11:30 am, Room 234, Physics Building

Host: Albert Chang

Abstract: In this talk two topics on spin and charge conduction in low-dimensional systems will be covered: (i) Resonant spin Hall conductance in quantum Hall systems; (ii) Anti-resonance and the 0.7 anomaly in charge conductance through a quantum point contact. In (i) we study transport properties of a two-dimensional electron system with Rashba spin-orbital coupling in a perpendicular magnetic field. The spin-orbital coupling competes with Zeeman splitting to introduce additional degeneracies between different Landau levels, gives rise to a resonant spin Hall conductance. In (ii) we investigate the transmission of electrons through a quantum point contact by using a quasi-one-dimensional model with a local bound state below the band bottom. The scattering from the bound state produces a wide zero-transmittance (anti-resonance) for the singlet formed by tunneling and local electrons, and has no effect on triplets, leading to a $0.75(2e^{2}/h)$ shoulder prior to the first $2e^{2}/h$ plateau. Formation of a Kondo singlet from electrons in the Fermi sea screens the local moment and reduces the effects of anti-resonance, complementing the shoulder from 0.75 to 1 at low temperatures.

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