Rodriguez Diego, Tsirlin Alexander A, Biesner Tobias, Ueno Teppei, Takahashi Takeshi, Kobayashi Kaya, Dressel Martin, Uykur Ece
1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany.
Experimental Physics VI, Center for Electronic Correlations and Magnetism, Augsburg University, 86159 Augsburg, Germany.
Phys Rev Lett. 2020 Apr 3;124(13):136402. doi: 10.1103/PhysRevLett.124.136402.
Employing high-pressure infrared spectroscopy we unveil the Weyl semimetal phase of elemental Te and its topological properties. The linear frequency dependence of the optical conductivity provides clear evidence for metallization of trigonal tellurium (Te-I) and the linear band dispersion above 3.0 GPa. This semimetallic Weyl phase can be tuned by increasing pressure further: a kink separates two linear regimes in the optical conductivity (at 3.7 GPa), a signature proposed for Type-II Weyl semimetals with tilted cones; this however reveals a different origin in trigonal tellurium. Our density-functional calculations do not reveal any significant tilting and suggest that Te-I remains in the Type-I Weyl phase, but with two valence bands in the vicinity of the Fermi level. Their interplay gives rise to the peculiar optical conductivity behavior with more than one linear regime. Pressure above 4.3 GPa stabilizes the more complex Te-II and Te-III polymorphs, which are robust metals.
利用高压红外光谱，我们揭示了元素碲的外尔半金属相及其拓扑性质。光导率的线性频率依赖性为三角碲（Te-I）的金属化以及3.0吉帕以上的线性能带色散提供了明确证据。这种半金属外尔相可以通过进一步增加压力来调节：一个扭结将光导率中的两个线性区域分开（在3.7吉帕处），这是为具有倾斜锥的II型外尔半金属提出的一个特征；然而，这在三角碲中揭示了一个不同的起源。我们的密度泛函计算没有发现任何明显的倾斜，并表明Te-I仍处于I型外尔相，但在费米能级附近有两个价带。它们的相互作用导致了具有多个线性区域的特殊光导率行为。4.3吉帕以上的压力使更复杂的Te-II和Te-III多晶型物稳定下来，它们是坚固的金属。
