ERA-Chemistry: Spin-polarized topological insulators under pressure

尽管固体的可压缩性很低，但热力学参数压力会显著影响化合物的稳定性及其结构和性能。在这项提案中，我们将解决固体物理前沿研究的焦点材料的高压改性问题，即拓扑绝缘体(TIS)。这些最近发现的非磁性材料代表了一种新的物质状态，使量子自旋霍尔态在正常条件下得以实现。这种状态支持体表面上空间分离的自旋极化通道，这些通道可以独立控制，并且可以在没有消相干的情况下传输信息。在磁性掺杂后，TIS可以呈现无耗散的量子化电流，有望在标准条件下实现量子计算的突破。确诊的TIS数量非常有限。一些理论研究表明，在压力下获得新的TiS是可能的，但到目前为止，补充的实验努力还很少。至于已知TiS的磁性掺杂，到目前为止，在几乎不受控制的合成条件下，在常压下进行的实验产生了非常温和的取代率(2-5at.%)。为了填补这些空白，我们建议：(A)探索选定的TI候选者在压力下的结构演变，例如层状异质结构，如BiTeI，(Bi2)n(BiTeI)m，(Bi2)n(Bi2Te3)m，(BiTeI)n(Bi2Te3)m(m，n大于或等于1)；(B)探索在确认的TiS(Bi2Te3，Bi2Se3)和上述TI候选者在压力下的磁性替代和磁性插层的可能性；将首先研究3D金属(铜、锰、铁、铬、钒)和稀土元素(Ce、Gd)；(C)寻找新的、可能是亚稳态的BiMx和SbMx的结构修饰，M=S，Se，Te，X=Cl，BrI。这项拟议的研究将通过增加钛的数量，特别是磁性掺杂钛的数量，对固态化学和物理做出重大贡献。

Despite the low compressibility of solids, the thermodynamic parameter pressure can notably influence the stability of compounds, their structure and properties. In this proposal we are going to tackle high-pressure modifications of materials that are in focus of the cutting-edge research in solid-state physics, namely topological insulators (TIs). These recently discovered non-magnetic materials represent a new state of matter that enables the quantum spin Hall state at normal conditions. This state supports spatially-separated spin-polarized channels on the bulk surface that can be controlled independently and can transmit information without decoherence. Upon magnetic doping, TIs can exhibit quantized electric current without dissipation, which promises breakthroughs in realization of quantum computing at standard conditions. The number of confirmed TIs is very limited. Some theoretical studies indicate a possibility to obtain new TIs under pressure, but the complementary experimental effort has so far been very scarce. As for magnetic doping of known TIs, experiments under normal pressure have so far yielded very modest substitution rates (2 to 5 at.%) under barely controlled synthetic conditions. In order to fill in these gaps we propose: (a) to explore structural evolution of selected TI-candidates, e. g. layered heterostructures such as BiTeI, (Bi2)n(BiTeI)m, (Bi2)n(Bi2Te3)m, (BiTeI)n(Bi2Te3)m (m, n greater or equal 1) under pressure; (b) to explore possibilities of magnetic substitution for Bi and magnetic intercalation in the confirmed TIs (Bi2Te3, Bi2Se3) and the abovementioned TI-candidates under pressure; 3d-metals (Cu, Mn, Fe, Cr, V) and rare-earth elements (Ce, Gd) will be investigated first; (c) to search for new, probably metastable, structural modifications of BiMX and SbMX, M = S, Se, Te, X = Cl, Br, I, under high-pressure conditions. The proposed research would contribute significantly to solid-state chemistry and physics by increasing the number of TIs and, especially, magnetically-doped ones.