Abstract
Transition-metal dipnictide PtBi2 exhibits rich structural and physical properties with topological semimetallic behavior and extremely large magnetoresistance (XMR) at low temperatures. We have investigated the electrical and magnetic properties of trigonal-phase PtBi2-x single crystals with x ~ 0.4. Profound de Haas–van Alphen (dHvA) and Shubnikov-de Haas (SdH) oscillations are observed. Through fast Fourier transformation (FFT) analyses, four oscillation frequencies are extracted, which result from α, β, γ, and δ bands. By constructing the Landau fan diagram for each band, the Berry phase is extracted demonstrating the non-trivial nature of the α, β, and δ bands. Despite Bi deficiency, we observe the Zeeman splitting in dHvA and SdH oscillations under moderate magnetic field and the moderate Landé g factor (4.97–6.48) for the α band. Quantitative analysis of the non-monotonic field dependence including the sign change of the Hall resistivity suggests that electrons and holes in our system are not perfectly compensated thus not responsible for the XMR effect.
Highlights
Transition-metal dipnictide PtBi2 can crystalize in multiple structures, including the cubic, hexagonal, and two orthorhombic phases.[1]
The cubic PtBi2 exhibits superconductivity.[5]. These rich phenomena seen in the cubic phase give rise to an important question: what is the role of the crystal structure in PtBi2? In other words, would properties be observed as in the cubic phase present in PtBi2 crystalized in different structures? For the trigonal PtBi2, both band calculations and angleresolved photoemission spectroscopy indicate the existence of linear dispersive Dirac bands located at Γ and M points,[6,7] which may be responsible for the linear field dependence of the magnetoresistance.[8]
~ 1:1.6, indicating Bi deficiency compared with the targeted stoichiometry
Summary
Transition-metal dipnictide PtBi2 can crystalize in multiple structures, including the cubic, hexagonal (or trigonal), and two orthorhombic phases.[1]. Similar behavior has been observed in a number of other non-magnetic materials in Dirac or Weyl semimetals with power close to 1/2.14,16–19 In the latter case, several mechanisms have been proposed to explain the resistivity upturn and the XMR effect at T < Tm, including the unique band structure involving Dirac bands,[20] electron–hole compensation,[21,22] a quantum phase transition,[16] gap opening at the band-touching points,[18,23] change of carrier concentration or mobility,[24] or normal scattering.[14]
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