Signatures of two-dimensional transport in superconducting nanocrystalline boron-doped diamond films

Nano-scale Transport Physics Laboratory and DST/NRF Centre of Excellence in Strong Materials, University of the Witwatersrand - Private Bag 3, WITS 2050, Johannesburg, South Africa

^(a) Somnath.Bhattacharyya@wits.ac.za

Received: 5 March 2018
Accepted: 22 June 2018

Abstract

The possibility of a two-dimensional (2D) phase is investigated in superconducting boron-doped nanocrystalline diamond films. The fluctuation spectroscopy schemes such as the Azlamazov-Larkin (AL) and Lerner-Varlamov-Vinokur (LVV) ones are used to determine the dimensionality crossovers occurring near the superconducting phase transition. It is found that a distinct 2D phase in the fluctuation regime occurs. One of the consequences of the 2D transport is the manifestation of the Berezinskii-Kosterlitz-Thouless (BKT) transition which is verified through both current voltage power law scaling as well as the Halperin-Nelson fitting to the temperature-dependent resistance. The suppression of the BKT transition with applied field is found to be correlated with the decrease of Josephson coupling between grains. The identification of a 2D phase accompanied by the BKT transition highlights the subtle effects of dimensionality in this unique system.