Volume 80, Number 3, November 2007
Article Number 37004
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 28 September 2007
EPL, 80 (2007) 37004
DOI: 10.1209/0295-5075/80/37004

Magnetic-field$\hbox{--}$induced singlet-triplet phase transition in quasi$\hbox{--}$one-dimensional organic superconductors

N. Belmechri1, G. Abramovici1, M. Héritier1, S. Haddad2 and S. Charfi-Kaddour2

1  Laboratoire de Physique des Solides, UMR 8502, CNRS Université Paris-Sud 11 - 91405 Orsay, France
2  Laboratoire de Physique de la Matière Condensée, Faculté des Sciences de Tunis - Tunisia

received 1 August 2007; accepted in final form 4 September 2007; published November 2007
published online 28 September 2007

We propose a theoretical model of quasi$\hbox{--}$one-dimensional superconductors, with attractive electron-electron interactions dominant in the singlet d-wave channel and sub-dominant in the p-wave channel. We discuss, in the mean-field approximation, the effect of a magnetic field applied perpendicularly to the direction of the lowest conductivity. The lowest free energy phase corresponds to a singlet d-wave symmetry in low fields, but to a triplet symmetry in high fields. A first-order singlet-triplet phase transition is expected at moderate applied fields of a few teslas. We propose to ascribe the recent critical field and NMR experimental data, observed in superconducting (TMTSF)2ClO4 to such an effect.

74.70.Kn - Organic superconductors.
74.25.Op - Mixed states, critical fields, and surface sheaths.
74.20.Rp - Pairing symmetries (other than s-wave).

© Europhysics Letters Association 2007