Events - Daily
December 19, 2012 >>
|Wednesday, December 19|
SPECIAL Condensed Matter Seminar - Inna Vishik, Stanford University - "Phase Competition in Cuprate Superconducting Dome"
The cuprate high temperature superconductors constitute one of the most difficult problems in condensed matter physics and a detailed experimental phenomenology is a crucial starting point for microscopic understanding. Angle-resolved photoemission spectroscopy (ARPES) measures electronic structure in momentum-space and is a powerful tool for investigating the cuprates because the key emergent phases—superconductivity and the normal state pseudogap—are characterized by momentum-dependent gaps in the spectra. A recent development in the ARPES technique involves using a UV laser as a light source, which allows one to measure the lowest lying excitations relevant to ground state properties. I will present recent experiments which constitute one of the most comprehensive ARPES studies to date, investigating spectral gaps as a function of temperature, doping, and momentum. At low temperature, we find evidence for three distinct quantum phases constituting the superconducting ground state at different dopings: one where superconductivity exists alone, one where superconductivity coexists with the pseudogap, and one where superconductivity coexists with another order distinct from the pseudogap. In the doping regime where superconductivity and pseudogap coexist, temperature dependence reveals that they compete below Tc in a momentum-dependent manner, which implies a new phase boundary of the pseudogap inside the superconducting dome. These experiments resolve conflicting reports about the cuprate phase diagram and provide stringent constraints on future theories explaining spectroscopic properties of emergent cuprate phases.
TBD · 1:30 p.m.– 2:30 p.m.