Bogoliubov Fermi surfaces from pairing of emergent $j=3/2$ fermions on the pyrochlore lattice

TL;DR

This paper investigates superconductivity in a strongly correlated pyrochlore lattice system, revealing a novel pairing state with Bogoliubov Fermi surfaces arising from $j=3/2$ fermions and $J=2$ quintet pairing.

Contribution

It introduces a new superconducting pairing mechanism in the pyrochlore lattice involving $j=3/2$ fermions and $E_g$ pairing, leading to Bogoliubov Fermi surfaces, which was not previously understood.

Findings

Favored $J=2$ quintet $E_g$ pairing state.

Time-reversal symmetry-breaking superconducting phase.

Presence of Bogoliubov Fermi surfaces.

Abstract

We examine the appearance of superconductivity in the strong-coupling limit of the Hubbard model on the pyrochlore lattice. We focus upon the limit of half filling, where the normal-state band structure realizes a $j=3/2$ semimetal. Introducing doping, we show that the pairing is favored in a $J=2$ quintet $E_g$ state. The attractive interaction in this channel relies on the fact that $E_g$ pairing on the pyrochlore lattice avoids the detrimental on-site repulsion. Our calculations show that a time-reversal symmetry-breaking superconducting phase is favored, which displays Bogoliubov Fermi surfaces.