Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 33: Superconductivity: Vortex Dynamics, Vortex Phases, Pinning
TT 33.1: Vortrag
Freitag, 31. März 2006, 10:15–10:30, HSZ 304
Fluxoid quantization effect on the specific heat of mesoscopic superconductors — •Florian Ong1, Olivier Bourgeois1, Sergey Skipetrov2, and Jacques Chaussy1 — 1CRTBT-CNRS 25 Avenue des Martyrs BP 166 38042 GRENOBLE cédex 9 France — 2LP2MC-CNRS (same address)
Up to now, despite their deep fundamental relevance, thermal properties of matter stuctured at the nanoscale have not received much attention. Here we present highly sensitive specific heat measurements of mesoscopic superconductors, at low temperature (down to 0.5 K) and under a tunable magnetic field (up to 1 T).
Our calorimeter is a thin suspended silicon membrane, containing a heater and a thermometer, on which nanostructures are deposited after an e-beam lithography. Using a temperature oscillation method and ultra low noise electronics, the resolution Δ C/C can reach 5.10−5.
We investigated thin Aluminium loops [1] and disks of 1 to 2.5 µ m in diameter, a size closed to the superconducting coherence length ξ (T) at 1 K. When sweeping the magnetic field H at a fixed temperature the behavior of the specific heat C is strongly governed by the fluxoid quantization. Indeed C(H) exhibits a periodicity of n × Φ0 (n is an integer depending on the temperature, and on the sample topology and size ; Φ0=h/2e is the superconducting flux quantum). These oscillations are the signatures of phase transitions between different vortex states, and can be described within the framework of the Ginzburg-Landau theory.
[1] O. Bourgeois, S. Skipetrov, F. Ong, J. Chaussy, Phys. Rev. Lett. 94, 0557007 (2005)