Superconductivity in potassium-doped 2,2$'$-bipyridine

TL;DR

This study demonstrates superconductivity in potassium-doped 2,2'-bipyridine with a transition temperature of 7.2 K, supported by magnetic susceptibility, resistance measurements, and Raman spectra, highlighting potential for organic superconductor development.

Contribution

First demonstration of superconductivity in potassium-doped 2,2'-bipyridine, revealing a new organic superconductor with a transition temperature of 7.2 K.

Findings

Superconductivity confirmed by Meissner effect and susceptibility measurements.

Resistance drops at the transition temperature, suppressed by magnetic fields.

Superconducting phase identified as K₃-2,2'-bipyridine via Raman spectra.

Abstract

Organic compounds are always promising candidates of superconductors with high transition temperatures. We examine this proposal by choosing 2,2$'$-bipyridine solely composed by C, H, and N atoms. The presence of Meissner effect with a transition temperature of 7.2 K in this material upon potassium doping is demonstrated by the $dc$ magnetic susceptibility measurements. The real part of the $ac$ susceptibility exhibits the same transition temperature as that in $dc$ magnetization, and a sharp peak appeared in the imaginary part indicates the formation of the weakly linked superconducting vortex current. The occurence of superconductivity is further supported by the resistance drop at the transition together with its suppression by the applied magnetic fields. The superconducting phase is identified to be K$_3$-2,2$'$-bipyridine from the analysis of Raman scattering spectra. This work not only opens an encouraging window for finding superconductivity after optoelectronics in 2,2$'$-bipyridine-based materials but also offers an example to realize superconductivity from conducting polymers and their derivatives.