将普通III-V和II-VI半导体化合物转化为拓扑异质结构：CdTe/InSb超晶格的情况
Transforming common III-V and II-VI semiconductor compounds into topological heterostructures: The case of CdTe/InSb superlattices
摘要：
目前已知的拓扑绝缘体（TI）限于掺入重元素的窄隙化合物，因此严重限制了可用于这种应用的材料池。我们通过第一性原理计算表明，如何由常见的半导体构建块制成的异价超晶格可以将其非TI组件转化为拓扑纳米结构，如III-V/II-VI超晶格InSb/CdTe。在没有界面原子交换的情况下，这种界面的异价性质建立了一个自然的内部电场，该电场与量子限制一起导致带反转，将这些半导体转化为拓扑相，同时也形成了巨大的Rashba自旋分裂。我们揭示了界面稳定性和拓扑转变之间的关系，找到了一个机会窗口，这两个条件都可以优化。当InSb层的临界厚度达到~ 1.5 nm时，[111]和[100]超晶格的相对能量都比原子交换界面高5-14 meV/A2，激发能隙高达~150 meV，从而在半导体超晶格中产生室温量子自旋霍尔效应。从这项研究中获得的理解可以通过创建下一代超结构功能材料来显着拓宽当前单个化合物的功能，而这些功能非常有限。
英文摘要：
Currently known topological insulators (TIs) are limited to narrow gap compounds incorporating heavy elements, thus severely limiting the material pool available for such applications. We show via first-principle calculations how a heterovalent superlattice made of common semiconductor building blocks can transform its non-TI components into a topological nanostructure, illustrated by III-V/II-VI superlattice InSb/CdTe. The heterovalent nature of such interfaces sets up, in the absence of interfacial atomic exchange, a natural internal electric field that along with the quantum confinement leads to band inversion, transforming these semiconductors into a topological phase while also forming a giant Rashba spin splitting. We reveal the relationship between the interfacial stability and the topological transition, finding a window of opportunity where both conditions can be optimized. Once a critical InSb layer thickness above ~ 1.5 nm is reached, both [111] and [100] superlattices have a relative energy of 5-14 meV/A2 higher than that of the atomically exchanged interface and an excitation gap up to ~150 meV, affording room-temperature quantum spin Hall effect in semiconductor superlattices. The understanding gained from this study could significantly broaden the current, rather restricted repertoire of functionalities available from individual compounds by creating next-generation super-structured functional materials.
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