Séminaire du LPTMS : Serguei Brazovski

Strong local and nonequilibrium events in electronic systems.

Serguei Brazovskii (LPTMS)

This review seminar will report on resent joint experimental/theoretical studies of low-dimensional electronic system with symmetry broken states in general, mostly electronic crystals, notably charge density waves, with extensions to superconductors. The selected observations will be related to strong, usually topologically nontrivial, perturbations of the order parameter under an external impact. The pattern may be either static, induced by either electric field or doping or disorder, or dynamic, under the optical pumping – a major recent trend in solid state physics.
Problems in temporal evolution and remnants of symmetry breaking phase transitions span subjects from high energy and cosmology to condensed matter. Recent optical study [1] of a far-from-equilibrium electronic charge ordering recovered coherent aperiodic undulations of the order parameter, critical slowing down of the collective mode, and evolution of the particle-hole gap. Numerical modeling with no fitting parameters allowed interpreting the observations, particularly the spatio-temporal distortions arising from “earthquakes” – annihilation events of topological defects in depth of the sample.
Strong perturbations are also recovered at the microscopic scale accessed by the new STM [2]; there are the amplitude solitons playing a role of neutral spin carriers – spinons. Their aggregation into solitonic lattices gives rise to modulated phases in spin-polarized superconductors or Charge Density Waves. Other experiments on nano-junctions and their modeling recover the intrinsic reconstruction by creating arrays of electronic vortices – dislocations.
[1] In collaboration with D. Mihailovic group, Ljubljana, Slovenia. Yusupov, et al, “Coherent dynamics of macroscopic electronic order through a symmetry breaking transition”, Nature Physics, 2010
[2] In collaboration with C, Brun (Paris-Nano center), Z.Z. Wang (LPN, Marcoussis), P. Monceau (Inst. Neel, Grenoble).  » Direct observation of spinons – the single-electron solitons – in an electronic solid  » , PRL 2012, to appear.

Date/Time : 10/01/2012 - 11:00

Location : LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay

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