Controllable Phase Slips in 3D Superconducting Diamond Microstructures

A superconducting phase slip is a topological fluctuation of the order parameter typically found in one-dimensional structures such as nanowires. They are the cause of a finite resistance below room temperature and can be detrimental to superconducting device performance. Recent work has sought to not only better understand, but to make use of these excitations. Current interest in phase slip physics from an applications perspective include metrology as a quantum current standard and in the proposed phase slip qubit – that uses quantum phase slips in place of Josephson junctions and so eliminate decoherence from noise associated with the barrier. A two-dimensional analogue of the phase slip centre – the so-called phase slip line – has previously been observed in thin-film metallic samples relatively close to the transition temperature. [1]<br/><br/>Here, we report on nonequilibrium excitations found in three-dimensional [2] structures fabricated from nanocrystalline superconducting boron-doped diamond structures that demonstrate the key features of one-dimensional phase slip centres over a wide temperature range [3]. More remarkably, we have demonstrated control over these excitations in that we are able to switch deterministically from the superconducting state to the normal state over a wide range of bias currents. We propose that the presence of phase slip-like excitations in a three-dimensional sample is supported by the unusual morphological columnar granularity of the nanocrystalline diamond films from which they are made being akin to a ‘naturally occurring’ 2D Josephson junction array. [4]<br/><br/>With similarities to both phase slip centres and lines, we suggest that these excitations may find use in a variety of settings, notably as a ‘barrier-less' Josephson junction.<br/><br/><b>References</b><br/><br/>[1] Sivakov, A. G., et al., Phys. Rev. Lett., 91.26 (2003): 267001.<br/>[2] Klemencic, G. M., et al. Phys. Rev. Mater. 1.4 (2017): 044801.<br/>[3] Klemencic, G. M., et al. <i>Carbon</i> 175 (2021): 43-49.<br/>[4] Klemencic, G. M., et al. <i>Sci. Rep. </i>9.1 (2019): 1-6.