Coupling of Spin and Orbital Motion of Electrons in Carbon Nanotubes - Condensed Matter > Mesoscale and Nanoscale PhysicsReport as inadecuate




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Abstract: Electrons in atoms possess both spin and orbital degrees of freedom. Innon-relativistic quantum mechanics, these are independent, resulting in largedegeneracies in atomic spectra. However, relativistic effects couple the spinand orbital motion leading to the well-known fine structure in their spectra.The electronic states in defect-free carbon nanotubes NTs are widely believedto be four-fold degenerate, due to independent spin and orbital symmetries, andto also possess electron-hole symmetry. Here we report measurementsdemonstrating that in clean NTs the spin and orbital motion of electrons arecoupled, thereby breaking all of these symmetries. This spin-orbit coupling isdirectly observed as a splitting of the four-fold degeneracy of a singleelectron in ultra-clean quantum dots. The coupling favours parallel alignmentof the orbital and spin magnetic moments for electrons and anti-parallelalignment for holes. Our measurements are consistent with recent theories thatpredict the existence of spin-orbit coupling in curved graphene and describe itas a spin-dependent topological phase in NTs. Our findings have importantimplications for spin-based applications in carbon-based systems, entailing newdesign principles for the realization of qubits in NTs and providing amechanism for all-electrical control of spins in NTs.



Author: F. Kuemmeth, S. Ilani, D. C. Ralph, P. L. McEuen

Source: https://arxiv.org/



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