Séminaire du LPTMS: A. Petkovic



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Fluctuations of the superconducting order parameter in two dimensions

A. Petkovic, ENS Paris

Transport properties of 2D superconducting systems can be very different from those of bulk superconductors because thermal and quantum fluctuations of superconducting order parameter are more pronounced and play a crucial role. First we focus on influence of superconducting fluctuations on dynamics, while the system is in the normal state but close to the superconducting transition. In the fluctuational regime, we derive Ginzburg-Landau-type action under far-from equilibrium conditions. Then, utilizing it, we calculate fluctuation-induced density of states and Maki-Thomson- and Aslamazov-Larkin-type contributions to the in-plane electrical conductivity [1,2]. We propose experimental setup where our results can be tested: thin superconducting film sandwiched between a gate and a substrate, which have different temperatures and different electrochemical potentials.

Then, we concentrate on transport at lower temperatures in close-to-equilibrium conditions investigating influence of quantum fluctuations on unbinding of vortex-untivortex pairs. We determine the temperature below which quantum fluctuations dominate over thermal fluctuations and describe the transport in this quantum regime. The crossover from quantum to classical regime is discussed and the quantum correction to the classical current-voltage relation is determined [3].

[1] Phys. Rev. Lett. 105, 187003 (2010)
[2] Phys. Rev. B 84, 064510 (2011)
[3] Phys. Rev. B 80, 212504 (2009)

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