Supression of electron correlations in the superconducting alloys of Rh$_{17-x}$Ir$_x$S$_{15}$

TL;DR

This study investigates how Iridium doping in Rh$_{17}$S$_{15}$ reduces electron correlations and alters superconducting and magnetic properties, indicating a decrease in density of states and suppression of the fishtail effect.

Contribution

It provides new insights into how Ir doping affects electron correlations and superconductivity in Rh$_{17}$S$_{15}$, a strongly correlated superconductor.

Findings

Reduction in density of states at the Fermi level.

Suppression of the fishtail effect in magnetization.

Altered resistivity behavior with a low-temperature minimum.

Abstract

We have studied the effect of Iridium doping (Rh$_{17-x}$Ir$_{x}$S$_{15}$) in the Rhodium sites of the strongly correlated superconductor Rh$_{17}$S$_{15}$. Even at low levels of doping (x = 1 and 2) we see a drastic change in the superconducting properties as compared to those of the undoped system. We deduce that there is a reduction in the density of states at the Fermi level from reduced Pauli susceptibility and Sommerfeld coefficient in the doped samples. Moreover, the second magnetization peak in the isothermal magnetization scan (`fishtail') which was very prominent in the magnetization data of the undoped crystal is suppressed in the doped samples. The temperature dependence of resistivity of the doped crystals show a remarkably different behavior from that of the undoped crystal with the appearance of a minima at lower temperatures, the position of which is fairly constant at different fields. Our data supports the notion that Iridium, which is a bigger atom than Rhodium expands the lattice thereby, reduces the electron correlations that existed due to the interaction between closer lying Rhodium atoms in the undoped system.