Fine frequency shift of sigle vortex entrance and exit in superconducting loops

Florian Ong (1) , Olivier Bourgeois (1) , S.E. Skipetrov (2) , Jacques Chaussy (1) , Simona Popa (3) , Jerome I. Mars (4) , Jean-Louis Lacoume (4)

1 NEEL - TPS - Thermodynamique et biophysique des petits systèmes
2 LPM2C - Laboratoire de physique et modélisation des milieux condensés
3 GIPSA-lab - Grenoble Images Parole Signal Automatique
4 GIPSA-SIGMAPHY - GIPSA - Signal Images Physique

The heat capacity $C_{p}$ of an array of independent aluminum rings has been measured under an external magnetic field $\vec{H}$ using highly sensitive ac-calorimetry based on a silicon membrane sensor. Each superconducting vortex entrance induces a phase transition and a heat capacity jump and hence $C_{p}$ oscillates with $\vec{H}$. This oscillatory and non-stationary behaviour measured versus the magnetic field has been studied using the Wigner-Ville distribution (a time-frequency representation). It is found that the periodicity of the heat capacity oscillations varies significantly with the magnetic field; the evolution of the period also depends on the sweeping direction of the field. This can be attributed to a different behavior between expulsion and penetration of vortices into the rings. A variation of more than 15\% of the periodicity of the heat capacity jumps is observed as the magnetic field is varied. A description of this phenomenon is given using an analytical solution of the Ginzburg-Landau equations of superconductivity.

Mots clés: calorimetry; votex; superconducting ring; nanophysics

Domaines: Systèmes mésoscopiques et effet Hall quantique [cond-mat.mes-hall]

Florian Ong, Olivier Bourgeois, S.E. Skipetrov, Jacques Chaussy, Simona Popa, et al.. Fine frequency shift of sigle vortex entrance and exit in superconducting loops. Physica C: Superconductivity and its Applications, 2007, 466 (1-2), pp.37-45. ⟨10.1016/j.physc.2007.05.050⟩. ⟨hal-00167711⟩