Fermi Surface Topology and Magneto-transport Properties of Superconducting Pd${}_3$Bi${}_2$Se${}_2$

Abstract

Pd${}_3$Bi${}_2$Se${}_2$ is a rare realization of a superconducting metal with a non-zero $Z_2$ topological invariant. We report the growth of high-quality single crystals of layered Pd${}_3$Bi${}_2$Se${}_2$ with a superconducting transition at $T_c$ ~ 0.80 K and upper critical fields of ~10 mT and ~5 mT for the in-plane and out-of-plane directions, respectively. Our density functional theory (DFT) calculations reveal three pairs of doubly degenerate bands crossing the Fermi level, all displaying clear three-dimensional dispersion consistent with the overall low electronic anisotropy (<2). The multiband electronic nature of Pd${}_3$Bi${}_2$Se${}_2$ is evident in magneto-transport measurements, yielding a sign-changing Hall resistivity at low temperatures. The magnetoresistance is non-saturating and follows Kohler's scaling rule. We interpret the magneto-transport data in terms of open orbits that are revealed in the DFT-calculated Fermi surface. de Haas-van Alphen (dHvA) oscillation measurements using torque magnetometry on single crystals yield four frequencies for out-of-plane fields: $F_{\alpha }=(150\pm 26)$T, $F_{\beta }=(293\pm 10)$T, $F_{\gamma }=(375\pm 20)$T, and $F_{\eta }=(1017\pm 12)$T, with the low frequency dominating the spectrum. Through the measurement of angular dependent dHvA oscillations and DFT calculations, we identify the $F_{\alpha }$ frequency with an approximately ellipsoidal electron pocket centered on the $L_2$ point of the Brillouin zone. Lifshitz-Kosevich analysis of the dHvA oscillations reveals a small cyclotron effective mass: $m^{\ast }=(0.11\pm 0.02)m_0$ and a nontrivial Berry phase for the dominant orbit. The presence of nontrivial topology in a bulk superconductor positions Pd${}_3$Bi${}_2$Se${}_2$ as a potential candidate for exploring topological superconductivity.

30 pages, 5 figures

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