PGI-1 Talk: Mira Ramakant Sharma

Quantum Theory of Materials Seminar

https://iffvc.fz-juelich.de/rooms/nat-ham-1kc-oip

Band topology and high g-factor anisotropy in crystals

We evaluate tight-binding analytical expressions to calculate the g tensor of electron and hole spins for group IV and III-V semiconductors with focus on crystalline Si, Ge and GaAs -- the leading hosts for gate-controlled spin qubits. Recalling that the electron g factor for bulk Si is +2 but -0.44 for bulk GaAs indicates the need to diagnose the occurrence of large variations in g. Mathematically, these values are singular values of the asymmetric g tensor. Using the determinant of g, det(g), as a diagnostic, we see large regions of k-space, for many bands in these semiconductors, where det(g) has an inverted sign. The topology of the surfaces where det(g) = 0 is particularly intricate in the case of the first conduction bands of Si and the second conduction band of Ge. We observe that these surfaces can be as complex as Fermi surfaces and share similar characteristics. We show that, considering just the spin contribution g_S to the g tensor, surfaces where det(g_S) = 0, which also commonly occur, indicate the occurrence of maximal spin-orbital entanglement in Bloch states.

Contact

Prof. Dr. Stefan Blügel
Phone: +49 2461 61-4249
Email: s.bluegel@fz-juelich.de

Mira Ramakant Sharma
Department of Physics, RWTH Aachen
Email: mrsharma@physik.rwth-aachen.de