Spectral Evidence for Emergent Order in Ba_{1-x}Na_{x}Fe_{2}As_{2}.

Author(s): Yi, M; Frano, A; Lu, DH; He, Y; Wang, Meng; Frandsen, BA; Kemper, AF; Yu, R; Si, Q; Wang, L; He, M; Hardy, F; Schweiss, P; Adelmann, P; Wolf, T; Hashimoto, M; Mo, S-K; Hussain, Z; Le Tacon, M; Bohmer, AE; Lee, D-H; Shen, Z-X; Meingast, C; Birgeneau, RJ | 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.