4 papers
Optically Active Fractional Wannier-Center Displacement Drives Giant Second-Harmonic Generation
Hongsheng Pang, Lixin He
Electric polarization is a static ground-state Berry-phase property, whereas second-harmonic generation (SHG) and shift current are dynamical optical responses. Their connection is…
Insulator-to-Metal Transitions Driven by Quantized Formal Polarization Mismatch
Hongsheng Pang, Lixin He
We propose a mechanism for insulator-to-metal (IM) transitions driven by the mismatch of quantized formal polarization (QFP), a symmetry-protected bulk invariant. For a material wi…
Quantized Polarization Redefines Polar Interfaces
Hongsheng Pang, Lixin He
In crystalline solids, the electronic polarization follows the \emph{generalized Neumann's principle}, under which all crystallographic point groups can, in principle, support ferr…
Generalized Neumann's Principle as a Unified Framework for Fractional Quantum and Conventional Ferroelectricity
Hongsheng Pang, Lixin He
Monolayer InSe exhibits unexpected in-plane polarization, despite having symmetry, a feature that was traditionally considered forbidden by symmetry. To explain thi…