Spectral Evidence for Emergent Order in Ba$_{1-x}$Na$_x$Fe$_2$As$_2$

TL;DR

This study uses angle-resolved photoemission spectroscopy to investigate the electronic structure of Ba$_{1-x}$Na$_x$Fe$_2$As$_2$, revealing orbital-dependent band shifts linked to nematic order and a novel electronic reconstruction associated with emergent magnetic order.

Contribution

It provides new insights into the electronic responses and emergent order parameters in the iron-based superconductor Ba$_{1-x}$Na$_x$Fe$_2$As$_2$, especially regarding the double-Q magnetic order.

Findings

Orbital-dependent band shifts follow lattice symmetry and vanish with C4 symmetry restoration.

Observation of a distinct electronic reconstruction not explained by known orders.

Identification of electronic responses associated with nematic and magnetic phases.

Abstract

We report an angle-resolved photoemission spectroscopy study of the iron-based superconductor family, Ba$_{1-x}$Na$_x$Fe$_2$As$_2$. This system harbors the recently discovered double-Q magnetic order appearing in a reentrant C$_4$ phase deep within the underdoped regime of the phase diagram that is otherwise dominated by the coupled nematic phase and collinear antiferromagnetic order. From a detailed temperature-dependence study, we identify the electronic response to the nematic phase in an orbital-dependent band shift that strictly follows the rotational symmetry of the lattice and disappears when the system restores C$_4$ symmetry in the low temperature phase. In addition, we report the observation of a distinct electronic reconstruction that cannot be explained by the known electronic orders in the system.