Polarons, Superconductivity and Molecular Electronics

An electron moving through a solid is impeded by its interaction with lattice vibrations. The resulting quasiparticle, the polaron, is of importance in many processes.

A novel continuous-time Monte-Carlo technique allowing for polaron and bipolaron simulations has led to the prediction of superlight lattice bipolarons (Alexandrov, Hague, Kornilovitch and Samson). Bose condensation of these bipolarons is a proposed mechanism for high-temperature superconductivity.

Flux cloning and vortex nucleation in small superconductors have been described by Gulevich, Kusmartsev and Sobnack. The results are in agreement with experiments by Geim and Grigorieva (Manchester). Kusmartsev has pioneered research in polaronic strings, stripes and electronic phase separation.

Another topic of research is the intrinsic molecular switching mechanism responsible for the bistable current state of some molecules (Alexandrov and Bratkovsky). This research (in collaboration with Hewlett-Packard) is potentially useful for new molecular technologies in the computing industries.

Some recent and current PhD theses

• Paul E Spencer, Continuous-time quantum Monte Carlo studies of lattice polarons, 2000 (supervisor Samson)
• Harjinder S Dhillon, A study of discrete nonlinear systems, 2001 (supervisor Kusmartsev)
• Christopher J Dent, Photoemission and Magnetic Response in the Bipolaronic Superconductors, 2001 (supervisor Alexandrov)
• Chanun Sricheewin, Small Fröhlich Polaron Green's Function and Tunnelling in Cuprates, 2001 (supervisor Alexandrov)
• Koun-Ken Lee (IRC in Superconductivity, Cavendish Laboratory, Cambridge), Kinetic Theory of Strongly-Coupled Electron-Phonon Systems, 2004 (supervisors Alexandrov and Liang, Cambridge)
• Kim Reynolds, Angle-Resolved Photoemission Spectroscopy of Band Tails in Doped Semiconductors, 2007 (supervisor Alexandrov)
• Tom Hardy, Superconductivity in the Hubbard-Froehlich Model, in progress (supervisors Alexandrov, Hague and Samson)
• Joanne Beanland, Tunnelling in High-Temperature Superconductors, in progress (supervisor Alexandrov)
• Steven Jackson, Electron pairing, in progress (supervisor Samson)

Contacts

• Sasha Alexandrov
• Dmitry Gulevich
• Viktor Kabanov
• Feo Kusmartsev
• Emmanuel Rashba
• John Samson
• Binoy Sobnack
• Vladimir Zavaritsky

For further information

A S Alexandrov, "Polarons and Bipolarons in Cuprates and Manganites", Plenary talk at 17th Annual Meeting of the German Crystallographic Society (Hannover, Germany. 9-12 March 2009) PowerPoint presentation (5.8 MB)

Jozef T Devreese and Alexandre S Alexandrov , Fröhlich polaron and bipolaron: recent developments, Rep. Prog. Phys. 72 066501 (2009) (has been downloaded 250 times in 19 days from the date of publication)

J P Hague, P E Kornilovitch, J H Samson and A S Alexandrov, Superlight Small Bipolarons in the Presence of a Strong Coulomb Repulsion, Phys Rev Lett 98 037002 (2007)

J P Hague, P E Kornilovitch, J H Samson and A S Alexandrov, Superlight small bipolarons, J Phys: Condens Matter 19 255214 (2007)

A S Alexandrov, Theory of Superconductivity: From Weak to Strong Coupling (IOP publishing, 2003)

A S Alexandrov (ed) Polarons in Advanced Materials (Springer Series in Materials Science, 2007)

S I Mukhin, A Mesaros, J Zaanen and F Kusmartsev, Enhanced electronic polarizability of metallic stripes and the universality of the bond-stretching phonon anomaly in high-temperature cuprate superconductors, Phys Rev B 76, 174521 (2007)

F Kusmartsev and M Saarela, What is the most important for a nanoscale structure formations in HTSC?, presented at LEHTSC 2007 spin, phonon or third way, J Phys: Conference Series 108 1-24 (2008) Video of the Invited Lecture

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