Peculiar band geometry induced giant shift current in ferroelectric SnTe monolayer 

Gan Jin & Lixin He 

npj Computational Materials 10: 23 (2024); Published online: 29 January 2024

Editorial Summary

Giant Photocurrent Effect in Two-Dimensional Ferroelectric SnTe: driven by the Monopole Quantum Potential Fields Arising from Peculiar Band Structures.

The Bulk Photovoltaic Effect (BPVE) is a phenomenon in which light-induced electrical current or voltage is generated in non-centrosymmetric materials, distinguishing it from traditional solar cells based on p-n junctions. The photovoltage produced by BPVE can exceed the material's bandgap, and its energy conversion efficiency potentially surpasses the Shockley–Queisser limit, thereby attracting widespread attention. The intrinsic contribution to BPVE is known as the shift current effect. Consequently, the search for materials with strong shift-current effects has become a hot topic in research. Researchers Jin, Gan and He, Lixin from the University of Science and Technology of China have successfully demonstrated a giant shift-current effect in the two-dimensional ferroelectric material SnTe, a discovery with the potential to profoundly impact solar energy conversion technology. Jin, Gan and He, Lixin investigated the nonlinear optical properties of monolayer SnTe using first-principles methods. They discovered that the giant shift-current effect originates from SnTe's peculiar band structure. Specifically, near the valley points of the material's band structure, the divergence of the 'shift vector' significantly influences nonlinear optical transitions. The shift vector characterizes the relative shift in position between the centers of electrons and holes generated during phototransitions. This divergent shift vector corresponds to a monopole-generated quantum potential field in the direct product space of the conduction and valence bands. This discovery not only proves that the physical effects caused by the divergence of shift vectors in semiconductor materials are measurable and significant, but it also provides valuable guidance for future research in the search for new materials with strong shift-current effects in the field of optoelectronic devices. 

编辑概述

二维铁电SnTe中的巨光电流效应：源自能带结构中的单极子量子势场

体积光伏效应（BPVE）是一种在非中心对称材料受光照时产生的光电流或光电压效应，这不同于传统的基于p-n结的太阳能电池。体光伏效应产生的光电压可以大于材料的带隙，并且其能量转换效率有潜力突破Shockley–Queisser极限，因而受到广泛关注。位移电流在体光伏效应中起着关键作用，寻找具有强位移电流效应的材料成为了当前研究的热点。中国科学技术大学的金敢和何力新成功揭示了在二维铁电材料SnTe中存在着巨大的位移电流效应，这一发现可能对太阳能转换技术产生深远影响。金敢和何力新运用第一性原理方法深入研究了SnTe单层材料的非线性光学特性。他们发现这种巨大的位移电流效应源于SnTe的非平凡能带结构。在材料能带结构中的谷点附近，位移矢量的发散对非线性光学跃迁产生了显著影响。位移矢量是光跃迁时，产生的电子和空穴中心位置的相对位移。该发散的位移矢量，对应于导带和价带的直积态空间中的一个单极子产生的量子势场。这一发现不仅证明了半导体材料中位移矢量发散引起的物理效应是可测量和显著的，而且为未来在光电设备领域中寻找具有强大位移电流效应的新材料提供了宝贵的指导。