Year: 2020
Type: article
Abstract: The Bloch theorem mathematically proves that in a periodic crystal, electrons can acquire a negative mass. The present work aims to provide a physical understanding for why this is so. We successively analyze the consequences of the threefold orbital valence-state coupling to (i) a nondegenerate orbital level in the conduction band, (ii) a threefold orbital level in the conduction band, and (iii) spin states through spin-orbit interaction. We show that it is not at all trivial for valence electrons to acquire a negative mass for whatever their momentum with respect to the crystal axes: It is necessary to not only have a coupling to a degenerate orbital conduction level but also a symmetry breaking of the threefold valence subspace by the spin quantization axis, as induced by spin-orbit interaction. Due to the relativistic origin of this interaction, the existence of negative valence masses thus constitutes an unexpected signature of quantum relativity.
Authors: Monique Combescot, Shiue-Yuan Shiau
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3025296395