Department of Superconductivity and Tunnel Spectroscopy
Head of the Department: Victor V.Chabanenko, doctor of physico-mathematical sciences (062) 311-00-25
Directions of Scientific Researches: Tunnel spectroscopy of superconductors and magneto-resistive materials; dynamics of a mixed state; electron and optical properties of the disordered structure systems including metal oxides with a disturbed long-range order.
Basic Results
Using the method of the Andreev spectroscopy there has been discovered an effect of increasing the relation 2Δ/kTc in high-temperature superconductors under pressure. A superconducting energy gap Δ in mercury (Tc = 135 K) and bismuth (Tc = 110 K) cuprates was demonstrated to increase under pressure quicker than critical temperature Tc.
This is indicative of an sentential contribution of the electron-phonon interaction into the mechanism of a high-temperature superconductivity.
Relying on a combined use of tunnel and Andreev spectroscopy, there has been experimentally proved a fundamental difference of physical mechanisms of the formation of an energy gap and pseudo gap in the spectrum of quasiparticles of high-temperature superconductors.
Using the method of tunnel spectroscopy there has revealed a nontrivial contribution of high-frequency phonon modes into the mechanism of high-temperature superconductivity. At high pressures there have been detected “nonstable” high-frequency phonon modes indicating of nano-sized stripe-structures in cuprate superconductors.
There have been studied the mechanisms of the formation of clusters in the technology of pulse laser precipitation. The processes taking place when a plasma flame is moving from a target to a base were demonstrated to have a dominant role there.
There has been studied the influence of laser radiation on the properties of the HTSC systems in different structure states, and an effect of changing-over the conductivity zones in the amorphous films YBaCuO has been found.
It has been shown that an ideal behavior of tunnel characteristics of the metal-insulator-metal contacts, the electrodes of which have small (of order of one electron-volt) Fermi energies, differs radically from a standard behavior which is to be expected at tunneling between common metals.
New effects have been detected in monocrystals YBaCuO with diagonal as to the transport current direction one-directed twins. The effects appear because of anisotropic pinning of a magnetic flux. The first (an odd one), as to a change of the magnetic field direction, contribution into a longitudinal electrical resistance is connected with the vortex lattice increase (guided vortex motion) by a twin structure. The other one, an even contribution into a diametrical electrical resistance, appears because of the influence of twins on the Hallow coefficient of the magnetic flux viscous flow.
Scientific cooperation
Nanoelectronics Laboratory, Graduate School of Engineering, Hokkaido University (Sapporo); Institute Fizyki PAN (Warszawa); L’Ecole Polytechnique (Paris).
Selected publications
1. A.I.Khachaturov, E.Hatta, V.M.Svistunov. Electron tunneling into a narrow band conductor. Journal Phys.Soc.Japan 72 (1), 131 (2003).
2. V.Chabanenko, A.Prodan, V.Shklovskij, et al.Experimental observation of a new galvanomagnetic effect in YbaCuO sinle crystals with unidirected twins. Supercond. Sci. Technol. 11, 1133 (1998).
3. V.D.Okunev, N.N.Pafomov. A non-linear percolation conductivity and a negative differential resistance in micro-crystalline layers with a changing-over charge pattern.- Zhurnal experimental’noi i teoreticheskoi fiziki, 116 (1), 276 (1999).
4. V.M.Svistunov, V.Yu.Tarenkov, A.I.D’yachenko e.a. Spectroscopy of quasi-particle excitations of a superconductive bismuth cuprate at high pressures.- Zhurnal experimental’noi i teoreticheskoi fiziki,, 113 (4), 1397 (1998).
5. V.M.Svistunov, M.A.Belogolovsky, A.I.Khachaturov. Electron-phonon interaction in high-temperature superconductors.- Uspehi fizicheskih nauk, 163 (2), 62 (1993).
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