Abstract
The unusual superconducting properties of granular aluminum oxide have been recently investigated for application in quantum circuits. However, the intrinsic irregular structure of this material requires a good understanding of the transport mechanisms and, in particular, the effect of disorder, especially when patterned at the nanoscale level. In view of these aspects, electric transport and voltage fluctuations have been investigated on thin-film based granular aluminum oxide nanowires, in the normal state and at temperatures between 8 and 300 K. The nonlinear resistivity and two-level tunneling fluctuators have been observed. Regarding the nature of the noise processes, the experimental findings give a clear indication in favor of a dynamic random resistor network model, rather than the possible existence of a local ordering of magnetic origin. The identification of the charge carrier fluctuations in the normal state of granular aluminum oxide nanowires is very useful for improving the fabrication process and, therefore, reducing the possible sources of decoherence in the superconducting state, where quantum technologies that are based on these nanostructures should work.
Highlights
Granular superconductors have attracted great interest for their rich phase diagram and for practical advantages, such as increased critical field [1], critical temperature [2,3], and kinetic inductance [4]
As a matter of fact, the kinetic inductance of an aluminum oxide (AlOx) wire is proportional to its normal state resistance and, can be orders of magnitude higher than its geometric inductance [6]
Such a super-inductance could be very useful for the realization of a novel type of superconducting quantum circuit with an impedance above the vacuum impedance, and it could be constructed from AlOx wires [5,7]
Summary
Granular superconductors have attracted great interest for their rich phase diagram and for practical advantages, such as increased critical field [1], critical temperature [2,3], and kinetic inductance [4]. Granular aluminum oxide (AlOx) has recently proven to play a prominent role in quantum electronics and in quantum bit (qubit) design due to its low electric loss and high kinetic inductance [5]. As a matter of fact, the kinetic inductance of an AlOx wire is proportional to its normal state resistance and, can be orders of magnitude higher than its geometric inductance [6]. Such a super-inductance could be very useful for the realization of a novel type of superconducting quantum circuit with an impedance above the vacuum impedance, and it could be constructed from AlOx wires [5,7]. The nanoscale structure can be advantageous in terms of electric loss, and in the limit of a short constriction can even be used as a non-linear element for quantum circuit design [8]
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