School of Physics and Technology, University of Jinan, Jinan, Shandong 250022, People's Republic of China.
Phys Chem Chem Phys. 2019 Feb 27;21(9):5165-5169. doi: 10.1039/c9cp00272c.
Ferroelasticity and band topology are two intriguing yet distinct quantum states of condensed matter materials. Their coexistence in a single two-dimensional (2D) lattice, however, has never been observed. Here, we found that the 2D tetragonal HfC monolayer allowed simultaneous presence of ferroelastic and topological orders. By using first-principles calculations, we found that it could allow a low switching barrier with reversible strain of 17.4%, indicating that the anisotropic properties are achievable experimentally for a 2D tetragonal lattice. More interestingly, the tuning of topological behaviors with strain led to spin-separated and gapless edge states, that is, the quantum spin Hall effect. These findings from the coupling of two quantum orders offer insights into ferroelastic control over topological edge states for achieving multifunctional properties in next-generation 2D nanodevices.
铁弹性和能带拓扑是凝聚态物质的两种有趣但不同的量子状态。然而，它们在单个二维（2D）晶格中的共存从未被观察到。在这里，我们发现二维四方 HfC 单层允许铁弹性和拓扑序同时存在。通过使用第一性原理计算，我们发现它可以允许低切换势垒和 17.4%的可逆应变，这表明对于二维四方晶格，各向异性特性是可以在实验中实现的。更有趣的是，应变对拓扑行为的调节导致了自旋分离且无能隙的边缘态，即量子自旋霍尔效应。这两种量子序的耦合为铁弹性控制拓扑边缘态以实现下一代二维纳米器件的多功能性提供了新的思路。
