Ferroic Berry Curvature Dipole in a Topological Crystalline Insulator at Room Temperature

Abstract

The physics related to Berry curvature is now a central research topic in condensed matter physics. The Berry curvature dipole (BCD) is a significant and intriguing condensed matter phenomenon that involves inversion symmetry breaking. However, the creation and controllability of BCDs have so far been limited to far below room temperature (RT), and nonvolatile (i.e., ferroic) BCDs have not yet been discovered, hindering further progress in topological physics. In this work, we demonstrate a switchable and nonvolatile BCD effect at RT in a topological crystalline insulator, Pb1–x Sn x Te (PST), which is attributed to ferroic distortion. Surprisingly, the magnitude of the ferroic BCD is several orders of magnitude greater than that of the nonferroic BCDs that appear, for example, in transition metal dichalcogenides. The discovery of this ferroic and extraordinarily large BCD in PST could pave the way for further progress in topological materials science and the engineering of novel topological devices.

Revealing a distortive polar order buried in the Fermi sea

“…In contrast, low-Sn PST behaved similar to an incipient ferroelectric with no complete phonon softening down to zero temperature. Future implementations of phase-sensitive second harmonic generation in the presence of a static electric field could clarify whether the observed distorted polar metal in PST exhibits a switchable polarization ( 54 ). The approach described here can be extended to identify inversion symmetry–breaking phase transitions in various types of polar and ferroelectric metals with displacive, order-disorder, or mixed characters ( 55 , 56 ).…”

Chirality-Tunable Nonlinear Hall Effect

“…Remarkable progress has also been made in realizing these effects experimentally. Nonlinear Hall signals have been recently revealed in transport measurements on van der Waals materials, − topological crystalline insulators, , and Dirac and Weyl semimetals. , Furthermore, the nonlinear Hall effect is expected to be of direct application in terahertz sensors and nonlinear devices. , …”