Electronic Raman scattering from orbital nematic fluctuations

TL;DR

This paper investigates how orbital nematic fluctuations in iron pnictides influence Raman scattering, revealing symmetry-dependent signatures near the nematic transition and a Lifshitz transition affecting spectral weight distribution.

Contribution

It provides a minimal model calculation showing the symmetry-specific Raman response due to orbital nematic fluctuations in iron pnictides.

Findings

Strong quasi-elastic scattering in B1g channel near Tn

No low-energy scattering in B2g symmetry

Spectral weight shift due to Lifshitz transition in B2g spectrum

Abstract

We compute Raman scattering intensities via the lowest-order coupling to the bosonic propagator associated with orbital nematic fluctuations in a minimal model for iron pnictides. The model consists of two bands on a square lattice exhibiting four Fermi pockets and a transition from the normal to a nematic state. It is shown that the orbital fluctuations produce in the B1g channel strong quasi-elastic light scattering around the nematic critical temperature Tn, both above and below Tn. This holds for the A1g symmetry only below Tn whereas no low-energy scattering from orbital fluctuations is found in the B2g symmetry. Due to the nematic distortion the electron pocket at the X-point may disappear at low temperatures. Such a Lifshitz transition causes in the B2g spectrum a large upward shift of spectral weight in the high energy region whereas no effect is seen in the other symmetries.