Weyl fermion excitations in the ideal Weyl semimetal CuTlSe2

Journal article

An ideal Weyl semimetal is characterized by a dispersion in which only Weyl cones intersect the Fermi level, with low-energy behavior being governed by Weyl fermions. Although ideal Weyl semimetals have long been anticipated, only a few are realized in nonmagnetic materials. In this study, we confirm the presence of Weyl-fermion excitations in the ideal Weyl semimetal CuTlSe₂ via a combination of magnetoresistance, Hall-effect, magnetic-susceptibility, nuclear magnetic resonance (NMR), and muon-spin relaxation (µ⁢SR) experiments. Magnetoresistance measurements reveal a negative longitudinal magnetoresistance (LMR), which scales as 𝐵2, while Hall-effect results indicate a predominant contribution from Weyl fermions with a hole-type charge. Magnetic susceptibility and µ⁢SR measurements indicate the lack of any intrinsic spontaneous magnetic moments down to base temperature. Finally, the NMR results can be modeled by a two-component effective Hamiltonian, which reproduces well the temperature-dependent ⁶³Cu NMR (𝑇_1⁢𝑇)⁻¹ factor, shown to scale as 𝑇² below 100 K and as 𝑇¹ above 100 K. Overall, we find that the extremely low concentration (10¹⁷cm⁻³) of carriers in CuTlSe₂ originates from an ideal nonmagnetic Weyl semimetallic state, persisting up to a thermal excitation energy of 9 meV (100 K), above which trivial electronic bands close to 𝐸_{F take over. Our findings highlight CuTlSe² as a new member of the intriguing class of Weyl semimetals.}

Authors: Wang, CN; Tay, D; Dong, QX; Okvátovity, Z; Huddart, BM

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review Research
• Volume: 6
• Issue: 3
• Article number: 033229
• Publication date: 2024-09-03
• Acceptance date: 2024-08-07
• DOI: 10.1103/physrevresearch.6.033229
• EISSN: 2643-1564
• ISSN: 2643-1564
• Language: English