"Observation of Temperature-Induced Crossover to an Orbital-Selective Mott Phase in AxFe2-ySe2 (A=K, Rb) Superconductors"

M. Yi: D. H. Lu, R. Yu, S. C. Riggs, J.-H. Chu, B. Lv, Z. K. Liu, M. Lu, Y.-T. Cui, M. Hashimoto, S.-K. Mo, Z. Hussain, C. W. Chu, I. R. Fisher, Q. Si, Z.-X. Shen; Physical Review Letters, 02/05/13.

Additional Authors: D. H. Lu, R. Yu, S. C. Riggs, J.-H. Chu, B. Lv, Z. K. Liu, M. Lu, Y.-T. Cui, M. Hashimoto, S.-K. Mo, Z. Hussain, C. W. Chu, I. R. Fisher, Q. Si, Z.-X. Shen

Abstract:

Using angle-resolved photoemission spectroscopy, we observe the low-temperature state of the AxFe2-ySe2 (A=K, Rb) superconductors to exhibit an orbital-dependent renormalization of the bands near the Fermi level—the dxy bands heavily renormalized compared to the dxz/dyz bands. Upon raising the temperature to above 150 K, the system evolves into a state in which the dxy bands have depleted spectral weight while the dxz/dyz bands remain metallic. Combined with theoretical calculations, our observations can be consistently understood as a temperature-induced crossover from a metallic state at low temperatures to an orbital-selective Mott phase at high temperatures. Moreover, the fact that the superconducting state of AxFe2-ySe2 is near the boundary of such an orbital-selective Mott phase constrains the system to have sufficiently strong on-site Coulomb interactions and Hund’s coupling, highlighting the nontrivial role of electron correlation in this family of iron-based superconductors.