Mottness at finite doping and charge instabilities in cuprates

• Published in: Nature physics Vol. 13; no. 8; pp. 806 - 811
• Main Authors: Peli, S., Conte, S. Dal, Comin, R., Nembrini, N., Ronchi, A., Abrami, P., Banfi, F., Ferrini, G., Brida, D., Lupi, S., Fabrizio, M., Damascelli, A., Capone, M., Cerullo, G., Giannetti, C.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.08.2017; Nature Publishing Group
• Subjects: 132/122; 140/125; 639/301/1034/1038; 639/301/119/2795; 639/624/1020/1095; 639/766/119/1003; 639/766/119/995; Atomic; Charge transfer; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Copper; Copper oxides; Cuprates; Degrees of freedom; Doping; Electrons; Low temperature; Mathematical and Computational Physics; Mean field theory; Molecular; Optical and Plasma Physics; Physics; Temperature effects; Theoretical
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys4112

The influence of Mott physics on the doping–temperature phase diagram of copper oxides represents a major issue that is the subject of intense theoretical and experimental efforts. Here, we investigate the ultrafast electron dynamics in prototypical single-layer Bi-based cuprates at the energy scale of the O-2 p → Cu-3 d charge-transfer (CT) process. We demonstrate a clear evolution of the CT excitations from incoherent and localized, as in a Mott insulator, to coherent and delocalized, as in a conventional metal. This reorganization of the high-energy degrees of freedom occurs at the critical doping p cr ≈ 0.16 irrespective of the temperature, and it can be well described by dynamical mean-field theory calculations. We argue that the onset of low-temperature charge instabilities is the low-energy manifestation of the underlying Mottness that characterizes the p < p cr region of the phase diagram. This discovery sets a new framework for theories of charge order and low-temperature phases in underdoped copper oxides. The electron dynamics of single-layer Bi 2 Sr 2− x La x CuO 6+ δ is studied as a function of doping, revealing the evolution of charge-transfer excitations from incoherent and localized (as in a Mott insulator) to coherent and delocalized (as in a conventional metal).