Bi kagome sublattice distortions by quenching and flux pinning in superconducting RbBi$_2$

TL;DR

This study investigates how quenching and flux pinning affect the structural and superconducting properties of RbBi$_2$, revealing that cooling rate influences local structure and vortex behavior without changing T$_c$.

Contribution

It provides new insights into the impact of cooling history on the local structure and flux pinning in RbBi$_2$, a superconductor with a kagome lattice.

Findings

Quenching induces distortions in Bi kagome sublattice.

Cooling rate affects local structure and magnetic susceptibility.

T$_c$ remains stable despite structural disorder.

Abstract

The properties of RbBi$_2$, a 4.15 K superconductor, were investigated using magnetic field, pressure and neutron diffraction. Under hydrostatic pressure, an almost 50 % reduction of T$_c$ is observed, linked to a low Debye temperature estimated at 165 K. The resistivity and magnetic susceptibility were measured on quenched and slow-cooled polycrystalline samples. The resistivity follows a low temperature power-law dependence in both types of samples, while the diamagnetic susceptibility, $\chi$, is dependent on the sample cooling history. Slow-cooled samples have a $\chi= -1$ while quenched samples have $\chi< -1$ due to grain size differences. Evidence of the effects of the cooling rate is also discerned from the local structure, obtained by neutron diffraction and the pair density function analysis. Slow-cooled samples have structurally symmetric Bi hexagons, in contrast to quenched samples in which disorder is manifested in periodic distortions of the Bi hexagonal rings of the kagome sublattice. Disorder may lead to flux pinning that reduces vortex mobility, but T$_c$ remains unaffected by the cooling rate.