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arXiv · 2110.01300

Detection of Weyl Fermions and the Metal to Weyl-Semimetal phase transition in WTe$_2$ via broadband High Resolution NMR

Wassilios Papawassiliou·José P. Carvalho·Hae Jin Kim·Chang-Yeon Kim·Seung Jo Yoo·Jin Bae Lee·Saeed Alhassan·Savvas Orfanidis·Vassilios Psycharis·Marina Karagianni·Michael Fardis·Nikolaos Panopoulos·Georgios Papavassiliou·Andrew J. Pell
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Abstract

Weyl Fermions (WFs) in the type-II Weyl Semimetal (WSM) WTe$_2$ are difficult to resolve experimentally because the Weyl bands disperse in an extremely narrow region of the (E-k) space. Here, by using DFT-assisted high-resolution $^{125}$Te solid-state NMR (ssNMR) in the temperature range $50$K - $700$K, we succeeded in detecting low energy WF excitations and monitor their evolution with temperature. Remarkably, WFs appear to emerge at T$\sim 120$K; at lower temperatures WTe$_2$ behaves as a metal. This intriguing metal-to-WSM phase transition is shown to be induced by the rapid raise of the Fermi level with temperature, crossing solely the electron and hole pockets in the low-T metallic phase, while crossing the Weyl bands near the nodal points - a prerequisite for the emergence of WFs - only for T$>120$K.

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Wassilios Papawassiliou, José P. Carvalho, Hae Jin Kim, Chang-Yeon Kim, Seung Jo Yoo, Jin Bae Lee, Saeed Alhassan, Savvas Orfanidis, Vassilios Psycharis, Marina Karagianni, Michael Fardis, Nikolaos Panopoulos, Georgios Papavassiliou, Andrew J. Pell. 2021-10-04. Detection of Weyl Fermions and the Metal to Weyl-Semimetal phase transition in WTe$_2$ via broadband High Resolution NMR. https://arxiv.org/abs/2110.01300

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