Quantization of intraband and interband Berry phases in the shift current

Abstract

The theory of the shift current has thus far been geometrical without being topological. This means that the real-space displacement of a photoexcited quasiparticle depends on the geometric Berry phase, but the Berry phase is not quantized to a rational multiple of $2\ensuremath{\pi}$ in any known material. The author rectifies this $s\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}s$ $q\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}o$ by introducing a new class of topological insulators whose wave-function topology is only compatible with materials lacking a center of inversion.

Topics & Concepts