Weyl fermion excitations in the ideal Weyl semimetal CuTlSe₂
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2024-07
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Journal Article
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Abstract
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 (µSR) 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 µSR 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 (T₁T)⁻¹ factor, shown to scale as T² below 100 K and as T¹ above 100 K. Overall, we find that the extremely low concentration (10¹⁷ cm⁻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.
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published
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Volume
6 (3)
Pages / Article No.
33229
Publisher
American Physical Society
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Subject
Giant magnetoresistance; Hall effect; Weyl semimetal; Muon spin resonance; Nuclear magnetic resonance; Nuclear magnetic resonance relaxation rate
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Funding
169455 - Exotic matter and correlated quantum phenomena (SNF)