Split Fermi Surfaces of the Spin–Orbit-Coupled Metal Cd₂Re₂O₇ Probed by de Haas–van Alphen Effect

The superconducting pyrochlore oxide Cd₂Re₂O₇ shows a structural transition with inversion symmetry breaking (ISB) at T_s1 = 200 K. A recent theory [L. Fu, Phys. Rev. Lett. 115, 026401 (2015)] suggests that the origin is an electronic instability that leads to a multipolar order in the spin–orbit-coupled metal. To observe the Fermi surface of the low-temperature phase of Cd₂Re₂O₇, we perform de Haas–van Alphen effect measurements by means of magnetic torque. In reference to a calculated band structure, the spin-split Fermi surfaces with large cyclotron masses of 5–9m₀ are revealed. The splitting is suggested to be due to an antisymmetric spin–orbit coupling induced by ISB, the strength of which is estimated to be approximately 67 K, which is rather smaller than those of typical non-centrosymmetric metals.