28 May 2014 Faraday effect due to Pauli exclusion principle in 3D topological insulator nanostructures
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3D topological insulator (3D TI) materials have interesting surface states that are protected against scattering due to non-magnetic impurities. They turn out to be useful in quantum information processing. Here, using the 3D Dirac equation, we show that the transitions between positive and negative energy solutions in a 3D TI heterostructure junction and in a 3D TI quantum dot (QD) obey strict optical selection rules. We calculate the optical conductivity tensor of a 3D TI double interface made of a PbTe/Pb0:31Sn0:69Te/PbTe heterostructure using Maxwell's equations, which reveals a giant Faraday rotation effect due to Pauli exclusion principle. A transfer matrix method is employed to calculate the transmittance in a multilayer stacking of PbTe/Pb0:31Sn0:69Te/PbTe heterostructure. We show that while the Faraday rotation is giant for a single double interface, it takes about 60 double interfaces to absorb incoming radiation completely. We also present the model of a QD consisting of a spherical core-bulk heterostructure made of 3D TI materials, such as PbTe/Pb0:31Sn0:69Te/PbTe , with bound massless and helical Weyl states existing at the interface and being confined in all three dimensions. We calculate the Faraday rotation effect coming from the polarization of single electron-hole pairs. We show that the semi-classical Faraday effect can be used to read out spin quantum memory.
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Hari P. Paudel, Michael N. Leuenberger, "Faraday effect due to Pauli exclusion principle in 3D topological insulator nanostructures", Proc. SPIE 9123, Quantum Information and Computation XII, 91230E (28 May 2014); doi: 10.1117/12.2050942; https://doi.org/10.1117/12.2050942

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