Orateur
Description
Boron-doped nanocrystalline diamond (BNCD) is a low-temperature granular superconductor with typical transition temperatures of order 3-5 K and upper critical fields of several tesla [1,2]. The superconductivity develops within a columnar, microstructured material whose superconducting properties are strongly dependent on growth conditions [2-4]. Microwave measurements also show a large sheet kinetic inductance, with L$_{k,□}$ ≈ 670–690 pH/□ for 500 nm thick films [1].
In granular BNCD, the fluctuation conductivity shows a characteristic dimensional crossover, as previously predicted for granular superconductors by Lerner, Varlamov, and Vinokur [2,3]. The shape of this crossover provides an alternative route to estimating otherwise hard-to-measure material parameters, in an early practical demonstration of “fluctuation spectroscopy” [2,3]. The distinctive critical exponent of resistance near $T_c$ also allows for precise estimation of $T_c$ itself. Applying this method to magnetoresistance measurements reveals the hallmarks of superconducting glass behaviour, further supported by magnetisation measurements [4].
When patterned into wide BNCD microbridges, a residual resistance and steps in the current-voltage characteristic are observed that are more commonly associated with one-dimensional superconducting nanowires [5,6]. Further experimental investigation into the voltage-carrying state in BNCD microbridges, along with simulations of the superconducting dynamics in the appropriate regime, supports the conclusion that these structures can host phase slip line excitations that straddle the width of the microbridge [5,6]. Here, I will present selected measurements of superconducting fluctuations, glassy behaviour, and phase-slip transport in BNCD films and microbridges fabricated from this disordered superconductor.
References
[1] J. A. Cuenca, et al., Carbon 201, 251–259 (2023).
[2] G. M. Klemencic, et al., Phys. Rev. Mater. 1, 044801 (2017).
[3] D. T. S. Perkins, et al., Phys. Rev. B 104, 094513 (2021).
[4] G. M. Klemencic, et al., Scientific Reports 9, 4578 (2019).
[5] G. M. Klemencic, et al., Carbon 175, 43–49 (2021).
[6] J. J. Bennett et al., Manuscript under review.