Theoretical Prediction of the Nematic Orbital-Ordered State in Ti-Oxypnictide Superconductor BaTi2(As,Sb)2O

TL;DR

This paper theoretically predicts a spin-fluctuation-driven orbital order in BaTi2(As,Sb)2O, explaining nematic states in multiorbital metals through the Aslamazov-Larkin vertex correction, aligning with recent experiments.

Contribution

It introduces a novel mechanism for nematic orbital order driven by spin fluctuations via AL-VC in Ti-oxypnictides.

Findings

Predicted intra-unit-cell nematic orbital order in BaTi2(As,Sb)2O.

The orbital order is driven by spin fluctuations and AL-VC.

The mechanism is likely universal in multiorbital metals.

Abstract

The electronic nematic state without magnetization emerges in various strongly correlated metals such as Fe-based and cuprate superconductors. To understand this universal phenomenon, we focus on the nematic state in Ti-oxypnictide BaTi2(As,Sb)2O, which is expressed as the three-dimensional 10-orbital Hubbard model. The antiferromagnetic fluctuations are caused by the Fermi surface nesting. Interestingly, we find the spin-fluctuation-driven orbital order due to the strong orbital-spin interference, which is described by the Aslamazov-Larkin vertex correction (AL-VC). The predicted intra-unit-cell nematic orbital order is consistent with the recent experimental reports on BaTi2(As,Sb)2O. Thus, the spin-fluctuation-driven orbital order due to the AL-VC mechanism is expected to be universal in various two- and three-dimensional multiorbital metals.