Seminars Archive

Surface-bulk dichotomy in single-layered Bi-based cuprates

Abstract
Structural supermodulations are a well-known complication in the phenomenology of single- and double-layered Bi-based cuprate compounds. It is also common (and dangerous!) practice to neglect such effects when it comes to charge dynamics in these materials. We studied under-to-optimally doped Bi2Sr2-xLaxCuO6 (x=0.8,0.6,0.5) compounds by means of surface probes: angle-resolved photoemission (ARPES), low-energy electron diffraction (LEED) - as well as bulk probes: resonant and non-resonant x-ray scattering and diffraction (REXS/XRD). The complementarity between single-particle electron spectroscopy and structural probes allowed us to unveil an unprecedented doping- and temperature-dependence of the superstructural wavevector, which is suggestive of the existence of a near-surface soft electronic phase in these materials. In particular, we determined that: (i) the abrupt emergence of new structural features with doping is driven by an electronic instability near the Fermi surface; (ii) reduced dimensionality effects at the surface drive an unconventional temperature-dependent modulation, which is not found in the bulk. Our results have profound implications on the understanding and interpretation of low-energy physics in underdoped cuprates. More details can be found at: http://arxiv.org/abs/1111.2673