高压下CrSb$_2$的Weyl半金属相及其高压多型体的结构压缩研究
Weyl Semimetallic Phase in High Pressure CrSb$_2$ and Structural Compression Studies of its High Pressure Polymorphs
AI总结：
本研究利用高压同步辐射X射线衍射研究了CrSb2两种高压多型体的结构，理论计算与高压电阻测量证实MoP2型多型体具有I型Weyl半金属性，为高压下过渡金属二磷族化物中寻找Weyl半金属开辟了新途径。
摘要：
本研究使用高压同步辐射粉末X射线衍射研究了CrSb2两种高压多型体的压缩情况。第一种是CuAl2型多型体，具有八配位Cr，可以从高压高温条件下淬火至常温常压条件。第二种是最近发现的MoP2型多型体，由室温压缩诱导产生，具有七配位Cr。在此，通过单晶X射线衍射解析，明确确认了所指派的结构。此外，对MoP2型多型体的电学性质进行了理论研究，并在CrSb2单晶上进行了高压下的电阻测量以配合压力下的电阻计算。本文讨论了MoP2型相的计算电子能带结构，并证明该多型体具有半金属性质并存在I型Weyl点。在高达50 GPa的压力下，CuAl2型结构未观察到进一步的相变；对于MoP2型结构，在40 GPa下也未观察到进一步相变。尽管CuAl2相具有最高的Cr配位数，但发现它比具有七配位Cr的MoP2相更难压缩，这归因于CuAl2型相中较长的Cr-Sb距离。在CrSb2中发现I型Weyl半金属相，为在高压下的过渡金属二磷族化物中寻找其他Weyl半金属开辟了道路。
英文摘要：
In this study, high pressure synchrotron powder X-ray diffraction is used to investigate the compression of two high pressure polymorphs of \ce{CrSb2}. The first is the \ce{CuAl2}-type polymorph with an eight-fold coordinated Cr, which can be quenched to ambient conditions from high-pressure high-temperature conditions. The second is the recently discovered \ce{MoP2}-type polymorph, which is induced by compression at room temperature, with a seven-fold coordinated Cr. Here, the assigned structure is unambiguously confirmed by solving it from single-crystal X-ray diffraction. Furthermore, the electrical properties of the \ce{MoP2}-type polymorph were investigated theoretically and the resistance calculations under pressure were accompanied by resistance measurements under high pressure on a single crystal of \ce{CrSb2}. The calculated electronic band structure for the \ce{MoP2}-type phase is discussed and we show that the polymorph is semimetallic and possesses type-I Weyl points. No further phase transitions were observed for the \ce{CuAl2}-type structure up to 50 GPa and 40 GPa for the \ce{MoP2}-type structure. Even though the \ce{CuAl2}-phase has the highest coordination number of Cr, it was found to be less compressible than the \ce{MoP2}-phase having a seven-fold coordinated Cr, which was attributed to the longer Cr-Sb distance in the \ce{CuAl2}-type phase. The discovery of a type-I Weyl semimetallic phase in \ce{CrSb2} opens up for discovering other Weyl semimetals in the transition metal di-pnictides under high pressure.
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