# Critical temperature and upper critical field of Li$_2$Pd$_{3-x}$Cu$_x$B (x=0.0, 0.1, 0.2)superconductors

## TL;DR

This study investigates how substituting Pd with Cu in Li$_2$Pd$_{3-x}$Cu$_x$B affects its superconducting properties, revealing a decrease in critical temperature and an enhancement of the upper critical field due to electron-phonon interactions and disorder.

## Contribution

It provides new insights into the effects of Cu substitution on the superconducting parameters of Li$_2$Pd$_{3-x}$Cu$_x$B, especially on the upper critical field behavior.

## Key findings

- Critical temperature decreases with more Cu content.
- Upper critical field is linear with temperature and exceeds WHH theory predictions.
- Enhancement of upper critical field is mainly due to electron-phonon coupling and disorder.

## Abstract

We studied the effects of substitution of Pd by Cu on the upper critical field of the noncentrosymmetric superconductor Li$_2$Pd$_{3-x}$Cu$_x$B, with x=0.0, 0.1 and 0.2. The upper critical field as a function of temperature was determined by resistance measurements at different magnetic fields. We found that the superconducting transition temperature decreases as the Cu content increases. Moreover, the temperature dependence of the upper critical field is linear in the range of the temperature studied and, at low temperature, is enhanced compared with the prediction of the Werthamer-Helfan-Hohenberg theory. This indicates that the breaking of Cooper pairs by spin orbit scattering and Pauli paramagnetism is negligible, and that the upper critical field enhancement is mainly because the electron-phonon coupling and disorder.