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Thomas Sand Jespersen: Spin-orbit coupling in multielectron carbon nanotube quantum dots

posted 19 Jul 2011, 03:39 by Peter Bøggild

Niels Bohr Institute, Nanophysics. Universitetsparken 5, Copenhagen Ø, Denmark. 

The coupling of the spin of electrons with their orbital motion is a central theme in quantum dot research. For carbon nanotubes the coupling was overlooked in the first decade of experiments. Recently, spin-orbit interactions were observed in a disorder-free few-electron quantum dot [1]. Here we demonstrate the spin-orbit coupling in the general multielectron regime (0-200) and in the presence of finite disorder [2].

The spin-orbit coupling is found to depend on the electron occupation of the dot in a systematic manner that follows from the curvature induced spin-orbit splitting of the Dirac cones for graphene. The modified spectrum is fully accounted for by a single-particle model. 

[1] F. Kuemmeth et al, Nature 452, 448 (2008). 
[2] T.S. Jespersen, K. Grove-Rasmussen et al, Nature Physics 7, 348 (2011)

Thomas Sand Jespersen obtained his masters degree in 2003 in physics from the Niels Bohr Institute and University of California, Berkeley, and obtained his PhD degree in 2007 from NBI and Harvard university, entitled  "Electron Transport in Semiconductor Nanowires and Electrostatic Force Microscopy on Carbon Nanotubes". He is currently assistant professor at Niels Bohr Institute, University of Copenhagen, working with low-temperature quantum transport in carbon nanotubes and semiconductor nanowires. His current interests include topological insulators and Majorana modes, spin-orbit effects (the relativistic coupling of the electron spin to its orbital motion) in carbon nanotubes and InAs nanowires, single-spin control in InAs nanowires and carbon nanotubes using electric fields, physics of superconductor/quantum dot/superconductor devices, where the quantum dot is usually formed in nanowires or nanotubes, (Universal) conductance fluctuations and Kondo physics in nanowires and scanning probe investigations and Raman spectroscopy of nano structures (nanowires, nanotubes, graphene).