Pressure and isotope effect on the anisotropy of MgB$_{2}$

TL;DR

This study investigates how pressure and boron isotope substitution affect the anisotropy and critical temperature of MgB$_{2}$ superconductors, revealing a universal relation linking these effects and uncovering a new property of anisotropic superconductors.

Contribution

It demonstrates that pressure and isotope effects on $T_c$ are directly related to changes in anisotropy, highlighting a novel property of anisotropic type II superconductors.

Findings

Pressure and isotope effects mirror changes in anisotropy.

Anisotropy is a key factor in Fermi surface renormalization.

A universal scaling relation connects $T_c$ shifts to anisotropy changes.

Abstract

We analyze the data for the pressure and boron isotope effect on the temperature dependence of the magnetization near $T_{c}$. Invoking the universal scaling relation for the magnetization at fixed magnetic field it is shown that the relative shift of $T_{c}$, induced by pressure or boron isotope exchange, mirrors essentially that of the anisotropy. This uncovers a novel generic property of anisotropic type II superconductors, inexistent in the isotropic case. For MgB$_{2}$ it implies that the renormalization of the Fermi surface topology due to pressure or isotope exchange is dominated by a mechanism controlling the anisotropy.