Superconductivity arising from pressure induced Lifshitz transition in Rb$_2$Pd$_3$Se$_4$ with kagome lattice

TL;DR

This study demonstrates pressure-induced superconductivity in Rb$_2$Pd$_3$Se$_4$, a kagome lattice compound, driven by a Lifshitz transition that alters its electronic structure without structural change, indicating unconventional superconductivity.

Contribution

It reveals that applying pressure induces a Lifshitz transition in Rb$_2$Pd$_3$Se$_4$, leading to superconductivity without structural phase change, highlighting a new pathway for superconductivity in kagome materials.

Findings

Superconductivity appears under high pressure in Rb$_2$Pd$_3$Se$_4$.

No structural transition occurs during the pressure-induced superconductivity.

Lifshitz transition causes the emergence of tiny Fermi surfaces at the Γ point.

Abstract

According to the Bardeen-Cooper-Schrieffer (BCS) theory, superconductivity usually needs well defined Fermi surface(s) with strong electron-phonon coupling and moderate quasiparticle density of states (DOS). A kagome lattice can host flat bands and topological Dirac bands; meanwhile, due to the parallel Fermi surfaces and the saddle points, many interesting orders are expected. Here, we report the observation of superconductivity by pressurizing a kagome compound Rb$_2$Pd$_3$Se$_4$ using a DAC anvil. The parent compound shows an insulating behavior; however, it gradually becomes metallic and turns to a superconducting state when a high pressure is applied. High pressure synchrotron measurements show that there is no structural transition occurring during this transition. The density-functional-theory (DFT) calculations illustrate that the insulating behavior of the parent phase is due to the crystalline field splitting of the partial Pd-4d $t_{2g}$ bands and the Se-derivative 4$p$-band. However, the threshold of metallicity and superconductivity are reached when the Lifshitz transition occurs, leading to the emergence of tiny Fermi surface at $\Gamma$ point. Our results point to an unconventional superconductivity and shed new light on understanding the electronic evolution of a kagome material.