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Superconductivity in Few Molecular Layer NbSe2

Speaker: 
Simon Bending (Bath University, UK)
Date: 
Mon, 02/06/2014 - 2:40pm to 3:20pm
Location: 
Graphene Seminar Room (S16 level 6)
Host: 
Goki Eda
Event Type: 
Seminars

Abstract

The isolation of graphene in 2004 has led to a dramatic renewal of interest in van der Waals bonded transition metal dichalcogenides. These exhibit a wide range of electronic ground states, e.g., superconducting, metallic, charge density wave and semiconducting, which can be tuned by varying the number of molecular layers and electrostatic doping. We describe systematic investigations of superconductivity in few molecular layer NbSe2 field effect transistors. All superconducting devices show multiple resistive transitions which we attribute to disorder in the layer stacking. The conductivity in the normal state and Tc both decrease as the electron concentration is increased with a back gate, consistent with a reduction in the density of states that is predicted theoretically. The magnetic field dependence of different resistive transitions allows values of the zero temperature upper critical field, Hc2(0), and coherence length, xi(0), to be independently estimated and compared. Results are interpreted in terms of available theoretical models.

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