title: Nonequilibrium phase transitions in cuprates observed by ultrafast electron crystallography.
abstract: Nonequilibrium phase transitions, which are defined by the formation of macroscopic transient domains, are optically dark and cannot be observed through conventional temperature- or pressure-change studies. We have directly determined the structural dynamics of such a nonequilibrium phase transition in a cuprate superconductor. Ultrafast electron crystallography with the use of a tilted optical geometry technique afforded the necessary atomic-scale spatial and temporal resolutions. The observed transient behavior displays a notable "structural isosbestic" point and a threshold effect for the dependence of c-axis expansion (Deltac) on fluence (F), with Deltac/F = 0.02 angstrom/(millijoule per square centimeter). This threshold for photon doping occurs at approximately 0.12 photons per copper site, which is unexpectedly close to the density (per site) of chemically doped carriers needed to induce superconductivity.
authors: Physical Biology Center for Ultrafast Science and Technology, California Institute of Technology (Caltech), Pasadena, CA 91125, USA.
authors: Nuh
authors: N
authors: Gedik
authors: Ding-Shyue
authors: DS
authors: Yang
authors: Gennady
authors: G
authors: Logvenov
authors: Ivan
authors: I
authors: Bozovic
authors: Ahmed H
authors: AH
authors: Zewail
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003300:Copper / Q000737:chemistry*; D003461:Crystallography / Q000295:instrumentation / Q000379:methods; D004583:Electrons; D007811:Lanthanum / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D044367:Phase Transition
chemical_list: C519316:La2CuO4; D010087:Oxides; D007811:Lanthanum; D003300:Copper; D010100:Oxygen