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Observation of Hexatic vortex fluid in a superconducting thin film

Instituto de Física de Líquidos y Sistemas Biológicos

Observation of Hexatic vortex fluid in a superconducting thin film

Expositor: Pratap Raychaudhuri
Tata Institute of Fundamental Research, Mumbai, India (

Viernes 18/12, 10:30hs.

In 1969, working on a theoretical problem of pure mathematical curiosity, David Thouless stumbled upon a new kind of phase transition, across which physical properties show abrupt change but the free energy varies smoothly. Very soon, Michael Kosterlitz and David Thouless realised that this kind of phase transition could be ubiquitous across 2-dimensional (2D) systems. For the particular case of a 2-dimensional crystalline solid, the (Berezinski)-Kosterlitz-Thouless (BKT) theory predicts the existence of a state intermediate between a solid and a liquid, called the hexatic fluid, which possesses the orientational order of a solid but the flow properties of a fluid. Here I will describe the realisation of hexatic vortex fluid in a very weakly pinned amorphous MoGe thin film [1]. I will discuss the properties of this hexatic vortex fluid and also discuss some very peculiar features of the vortex states revealed from STS and transport measurements [2,3,4].

[1] Melting of the Vortex Lattice through Intermediate Hexatic Fluid in an a-MoGe Thin Film, Indranil Roy, Surajit Dutta, Aditya N. Roy Choudhury, Somak Basistha, Ilaria Maccari, Soumyajit Mandal, John Jesudasan, Vivas Bagwe, Claudio Castellani, Lara Benfatto, and Pratap Raychaudhuri, Phys. Rev. Lett. 122, 047001 (2019).
[2] Extreme sensitivity of the vortex state in a-MoGe films to radio-frequency electromagnetic perturbation, Surajit Dutta, Indranil Roy, Soumyajit Mandal, John Jesudasan, Vivas Bagwe, and Pratap Raychaudhuri, Phys. Rev. B 100, 214518 (2019).
[3] An inertial model of vortices to explain the extreme sensitivity of hexatic vortex fluid to low frequency ac excitation, Surajit Dutta and Pratap Raychaudhuri, Physica C 578, 1353740 (2020).
[4] Collective flux pinning in hexatic vortex fluid in a-MoGe thin film, Surajit Dutta, Indranil Roy, Somak Basistha, Soumyajit Mandal, John Jesudasan, Vivas Bagwe and Pratap Raychaudhuri, J. Phys.: Condens. Matter 32, 075601 (2020).

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