Anomalous dielectric response in insulators with the pi Zak phase

TL;DR

This paper demonstrates that insulators with the pi Zak phase exhibit an anomalous dielectric response, characterized by large polarization jumps, due to boundary states, with theoretical and ab initio evidence across various materials.

Contribution

It reveals a universal anomalous dielectric response in insulators with the pi Zak phase, supported by theoretical models and ab initio calculations for real materials.

Findings

Large polarization jumps near e/2 in 1D models

Pi Zak phase associated with half-filled edge states

Anomalous response observed in diamond, silicon, and PTFE

Abstract

In various topological phases, nontrivial states appear at the boundaries of the system. In this paper, we investigate anomalous dielectric response caused by such states caused by the pi Zak phase. First, by using the one-dimensional Su-Schrieffer-Heeger model, we show that, when the system is insulating and the Zak phase is pi, the polarization suddenly rises to a large value close to e/2, by application of an external electric field. The pi Zak phase indicates existence of half-filled edge states, and we attribute this phenomenon to charge transfer between the edge states at the two ends of the system. We extend this idea to two- and three-dimensional insulators with the pi Zak phase over the Brillouin zone, and find similar anomalous dielectric response. We also show that diamond and silicon slabs with (111) surfaces have the pi Zak phase by ab intio calculations, and show that this anomalous response survives even surface reconstruction involving an odd number of original surface unit cells. Another material example with an anomalous dielectric response is polytetrafluoroethylene (PTFE), showing plateaus of polarization at +e by ab initio calculation, in agreement with our theory.