Pressure tuning of Fermi surface topology of optimally doped BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$

TL;DR

This study explores how applying pressure alters the Fermi surface topology and suppresses superconductivity in optimally doped BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$, revealing a transition from tetragonal to collapsed tetragonal phase.

Contribution

It demonstrates pressure-induced Fermi surface topology changes and their impact on superconductivity in an iron-based superconductor, linking structural, electronic, and magnetic properties.

Findings

Superconductivity vanishes at 7.5 GPa coinciding with a structural phase transition.

Pressure suppresses antiferromagnetic spin fluctuations and quasiparticle effective mass.

Fermi surface topology modification under pressure correlates with superconductivity suppression.

Abstract

The superconducting, transport, and structural properties of optimally electron-doped BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$ are investigated by combining the electrical resistance and synchrotron X-ray diffraction measurements at high pressures. The superconducting transition temperature of this system is found to decrease in a similar way of the axial ratio of $c/a$ with increasing pressure but vanishing at a critical pressure of 7.5 GPa where $c/a$ has a dip and an isostructural transformation from a tetragonal to a collapsed tetragonal phase takes place. The resistance is found to obey a linear temperature dependence, evidencing the antiferromagnetic spin-fluctuations transport mechanism. The pressure effects are interpreted within the framework of pressure-induced Fermi surface topology modification in which pressure suppresses both the quasiparticle effective mass and the strength of the antiferromagnetic spin fluctuations leading to the reduction of superconductivity, accordingly. The absent superconductivity in the collapsed tetragonal phase is suggested to result from the complete suppression of the antiferromagnetic spin fluctuations.