Revealed by ARPES and REXS Studies

Transition metal pnictides in 122 families are rich with fantastic quantum phenomena such as spin density wave (SDW) in BaFe₂As₂[1], superconductivity (SC) and charge density wave (CDW) in SrPt₂As₂[2] and BaPt₂As₂[3]. In the meanwhile, BaPt₂As₂ and SrPt₂As₂ shares CaBe₂Ge₂-type structure while BaFe₂As₂ crystallizes in ThCr₂Si₂-type structure. Studying the interplay among SDW, SC and CDW and their relationship with crystal structure and structural transition is of wide interests. BaAg₂As₂, as a newly-discovered transition metal pnictide adopted to ThCr₂Si₂-type structure, possess a phase transition at 138K in resistivity whose origin is still unknown[4]. To study the mechanism, we applied systematic angle-resolved photoemission spectroscopy (ARPES) combined with resonant elastic soft X-ray scattering (REXS) and identified the exact structural transition and density-wave-like transition in it for the first time.

[1] M. Rotter, et al., Phys. Rev. B 78, 020503(R) (2008).
[2] W.B. Jiang, et al. J. Phys.: Condens. Matter 27.2 (2014): 022202.
[3] Kudo, et al. J. Phys. Soc. Jpn 79.12 (2010): 123710.
[4] Stoyko, et al. J. Solid State Chem. 194 (2012): 113-118.