Cooling a polaronic liquid: Phase mixture and pseudogap-like spectra in superconducting Ba1−xKxBiO3

M. Naamneh, M. Yao, J. Jandke, J. Ma, Z. Ristić, J. Teyssier, A. Stucky, D. van der Marel, D. J. Gawryluk, T. Shang, M. Medarde, E. Pomjakushina, S. Li, T. Berlijn, S. Johnston, M. Müller, J. Mesot, M. Shi, M. Radović, N. C. Plumb

Research output: Working paperPreprint


Many complex electronic systems exhibit so-called pseudogaps, which are poorly-understood suppression of low-energy spectral intensity in the absence of an obvious gap-inducing symmetry. Here we investigate the superconductor $Ba_{1-x}K_{x}BiO_{3}$ near optimal doping, where unconventional transport behavior and evidence of pseudogap(s) have been observed above the superconducting transition temperature $T_{c}$, and near an insulating phase with long-range lattice distortions. Angle-resolved photoemission spectroscopy (ARPES) reveals a dispersive band with vanishing quasiparticle weight and "tails" of deep-energy intensity that strongly decay approaching the Fermi level. Upon cooling below a transition temperature $T_{p} > T_{c}$, which correlates with a change in the slope of the resistivity vs. temperature, a partial transfer of spectral weight near $E_{F}$ into the deep-binding energy tails is found to result from metal-insulator phase separation. Combined with simulations and Raman scattering, our results signal that insulating islands of ordered bipolarons precipitate out of a disordered polaronic liquid and provide evidence that this process is regulated by a crossover in the electronic mean free path.
Original languageEnglish
StatePublished - 2018

Publication series

NamearXiv preprint arXiv:1808.06135‏


  • cond-mat.supr-con


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