Signature of Unconventional Superconductivity in a Copper-based Metal-Organic Framework with Perfect Kagome Structure

TL;DR

This paper reports evidence of unconventional superconductivity in a copper-based metal-organic framework with a perfect Kagome lattice, revealing non-Fermi liquid behavior and low-energy quasiparticle excitations.

Contribution

It provides high-precision measurements showing unconventional superconductivity in Cu-BHT MOF with a Kagome lattice, highlighting its potential for studying quantum spin liquids.

Findings

Non-exponential, quasi-linear temperature dependence of penetration depth

Evidence of low-energy quasiparticle excitations

Non-Fermi liquid behavior observed in the system

Abstract

Recently, the superconductivity in a metal-organic framework (MOF) has been discovered for the first time in copper(II) benzenehexathiolate ([Cu$_3$(C$_6$S$_6$)]$_n$, Cu-BHT). The Cu atoms form a two-dimensional perfect Kagome lattice, which has the potential to host a metallic quantum spin liquid state. Here we present high-precision measurements of in-plane magnetic penetration depth $\lambda$ in Cu-BHT films down to 40\,mK. The temperature dependence of $\lambda$ shows a non-exponential, quasi-linear behavior at low temperatures, suggesting that unconventional superconductivity with low-energy quasiparticle excitations is realized in this system. With the reported non-Fermi liquid behavior, this finding implies that MOFs can provide a flexible platform to investigate the superconducting pairing mechanisms in the presence of spin frustration and strong quantum fluctuations.