Realization of Z₂ Topological Metal in Single‐Crystalline Nickel Deficient NiV₂Se₄

Abstract

Temperature-dependent electronic and magnetic properties are reported for nickel-deficient NiV 2 Se 4 . Single-crystal X-ray diffraction shows it to crystallize in the monoclinic Cr 3 S 4 structure type with space group I2∕m and vacancies on the Ni site, resulting in the composition Ni 0.85 V 2 Se 4 in agreement with our electron-probe microanalysis. Structural distortions are not observed down to 1.5 K. Nevertheless, the electrical resistivity shows metallic behavior with a broad anomaly around 150-200 K that is also observed in the heat capacity data. This anomaly indicates a change of state of the material below 150 K. It is believed that this anomaly could be due to spin fluctuations or charge-density-wave fluctuations, where the lack of long-range order is caused by vacancies at the Ni site of Ni 0.85 V 2 Se 4 . The non-linear temperature dependence of the resistivity as well as an enhanced value of the Sommerfeld coefficient 𝜸 = 104.0 (1) mJ mol −1 K −2 suggest strong electron-electron correlations in this material. First-principles calculations performed for NiV 2 Se 4 , which are also applicable to Ni 0.85 V 2 Se 4 , classify this material as a topological metal with Z 2 = (1; 110) and coexisting electron and hole pockets at the Fermi level. The phonon spectrum lacks any soft phonon mode, consistent with the absence of periodic lattice distortion in the present experiments.

Room Temperature Charge Density Wave in a Tetragonal Polymorph of Gd2Os3Si5 and Study of Its Origin in the RE2T3X5 (RE = Rare Earth, T = Transition Metal, X = Si, Ge) Series

“…Examples include CuV 2 S 4 , NiV 2 Se 4 , ErTe 3 . 51,117,118 Figure 13 collects all materials where there are no structural transitions reported due to a lack of evidence from measurements. Many of these compounds that fall within the criterion are the RE 2 Rh 3 Si 5 series, which are reported to exhibit AFM transitions from the physical properties.…”

“…Suppression of CDW is known to occur in materials with chemical disorders or defects like vacancies. Examples include CuV 2 S 4 , NiV 2 Se 4 , ErTe 3 . ,, …”