Frank Laboratory of Neutron Physics

Joint Laboratory Seminar

Leader – V.N. Shvetsov

Date and Time: Thursday, 25 January 2018, at 3:00 PM

Venue: Conference hall (3rd floor), Frank Laboratory of Neutron Physics

Seminar topic: «Spectra of magnetic and lattice excitations in high-temperature superconductors»

Speaker: Alexander S. Ivanov (Peter the Great St.Petersburg Polytechnic University, St.Petersburg Russia; Institut Laue-Langevin, Grenoble, France)

Abstract:

Spectra of lattice vibrations and magnetic fluctuations in several families of copper- and iron-based high-temperature superconductors have been measured by inelastic neutron scattering. It is found that ionic coupling is dominating in cuprates with vibrations screened by free electrons when injected as a function of composition. Effects of electron-phonon interaction are present but not pronounced. Low energy magnetic excitations in antiferromagnetic stoichiometric cuprates with symmetric (tetragonal) crystal structures are described by introducing short-range pseudo-dipolar interactions. Magnetic resonance excitation (spin resonance) is shown to be of universal nature in the superconducting state of different families of new superconducting materials. The resonance spectral weight is described using an itinerant electron model with a superconducting gap of particular symmetry different from that of conventional superconductors with electron-phonon interaction mechanism.

(Following the thesis materials for obtaining a degree of Doctor of physical and mathematical sciences)