Volume 78, Number 4, May 2007
Article Number 47001
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 03 May 2007
EPL, 78 (2007) 47001
DOI: 10.1209/0295-5075/78/47001

Thermodynamically stable noncomposite vortices in mesoscopic two-gap superconductors

L. F. Chibotaru, V. H. Dao and A. Ceulemans

Division of Quantum and Physical Chemistry and INPAC, Institute for Nanoscale Physics and Chemistry, University of Leuven - Celestijnenlaan, 200F, B-3001 Leuven, Belgium

received 6 March 2007; accepted in final form 5 April 2007; published May 2007
published online 3 May 2007

In mesoscopic two-gap superconductors with sizes of the order of the coherence length noncomposite vortices are found to be thermodynamically stable in a large domain of the T-H phase diagram. In these phases the vortex cores of one condensate are spatially separated from the other condensate ones, and their respective distributions can adopt distinct symmetries. The appearance of these vortex phases is caused by a non-negligible effect of the boundary of the sample on the superconducting order parameter and represents therefore a genuine mesoscopic effect. For low values of interband Josephson coupling vortex patterns with $L_{1} \ne L_{2}$ can arise in addition to the phases with L1 =L2, where L1 and L2 are total vorticities in the two condensates. The calculations show that noncomposite vortices could be observed in thin mesoscopic samples of MgB2.

74.78.Na - Mesoscopic and nanoscale systems .
74.20.De - Phenomenological theories (two-fluid, Ginzburg-Landau, etc.) .
74.25.Ha - Magnetic properties .

© Europhysics Letters Association 2007