Superconductivity arising from pressure-induced emergence of a Fermi surface in the kagome-lattice chalcogenide Rb2Pd3Se4

According to the Bardeen-Cooper-Schrieffer theory, superconductivity usually needs well-defined Fermi surface(s) with strong electron-phonon coupling and moderate quasiparticle density of states. A kagome lattice can host flat bands and topological Dirac bands; meanwhile, due to the parallel Fermi surfaces and saddle points, many interesting orders are expected. Here, we report the observation of superconductivity by pressurizing a kagome compound Rb2Pd3Se4 using a diamond-anvil-cell. The parent compound shows an insulating behavior; however, it gradually becomes metallic and turns to a superconducting state when high pressure is applied. High-pressure synchrotron measurements show that there is no structural transition occurring during this process. The density-functional-theory calculations illustrate that the insulating behavior of the parent phase is due to the crystalline field splitting of the partial Pd-4d t2g bands and the Se-derivative 4p band. However, the threshold of metallicity and superconductivity are reached when the Lifshitz transition occurs, leading to the emergence of a tiny Fermi surface at the I' point. Our results point to an unconventional superconductivity and shed light on understanding the electronic evolution of a kagome material.

Automated summary

This study reports the observation of unconventional superconductivity in a kagome compound Rb2Pd3Se4 by applying high pressure. The insulating behavior of the parent phase is attributed to the crystalline field splitting of partial bands, while the thresholds for metallicity and superconductivity are reached during the Lifshitz transition.