CP ANNUAL REPORT (2008)

RESEARCH

· A thermodynamic theory of the phases and phase transitions in a wide class of inter-metallic compounds – ferromagnetic superconductors with unconventional (spin-triplet) Cooper pairing of d- and/or f-electrons has been developed. The phases and the shape of the phase diagrams of this class of systems is described in some details in conformity with the recent experimental data. A quantitative criterion allowing for the classification of these materials in two different types with quite distinguishable physical properties is deduced from our thermodynamic theory [1, 2].

· A quite general theory of fluctuation correlations has been developed on the basis of a cumulant expansion. The theory can be applied to a wide class of lattice models of many-body systems. This approach allows for a more precise derivation of effective field theories and sheds some light on the interpretation of known approximations in theoretical physics such as, for example, the mean-field approximation. We have obtained corrections to the Landau parameters (vertex parameters) of the effective field theory corresponding to the Ising model with both short and long range inter-spin interactions [3].

· Gauge effects on the fluctuation properties of the normal-to-superconducting phase transition in bulk and thin film superconductors are reviewed in a Chapter of book [4] published in 2008 (see our 2007 ISSP report).

PAPERS

1. D. I. Uzunov, Europhys. Lett. 77 (2007) 20008, “New magnetic effects on the phase transitions in unconventional superconductors.” [epl_20008.pdf]

2. M. G. Cottam, D. V. Shopova, and D. I. Uzunov, Phys. Lett. A 373 (2008) 152-155. “On the phase diagrams of the ferromagnetic superconductors ZrZn2 and UGe2.” [PLA_2008.pdf]

3. D. I. Uzunov, Phys. Rev. E 78 (2008) 041122. “Derivation of effective field theories.” [PRE_2008.pdf]

4. D. V. Shopova and D. I. Uzunov, (First Chapter in book), in: Progress in Superconductivity Research, edited by Oliver A. Chang ( Nova Science Publishers, New York, 2008), pp. 1 -75; ISBN: 1-60021-694-3. Title: “Large Fluctuation and Gauge Effects on the Critical Behaviour of Superconductors.” See [arXiv:.pdf]

CURRENT PROJECTS, GRANTS

· Phases and phase transitions in super-fluids, superconducting and magnetic materials
(Research contract, Central Administration of BAS).

· National Foundation of Scientific Research Grant “Physics 1507/05: Coexistence of spin-triplet superconductivity and ferromagnetism in some metallic compounds.”

INTERNATIONAL COLLABORATION

· Collaborative visit (4 months): University of Western Ontario (London, ON, Canada).

· Teaching in four lecture courses within the MS program of the African University of Science and Technology (Abuja, Nigeria).

· A number of referee reports for international publishers: American Physical Society (APS): PRL, PRB ; Institute of Physics (IoP): J. Phys. A, J. Physics: Condensed Patter, J. Phys. B, D, NJP. Ukrainian Acad. Of Sciences: Journal of Physical Studies.