Abstract
In this study, we investigated the electrical transport properties of niobium titanium nitride (NbTiN) nanowire with four-terminal geometries to clarify the superconducting phase slip phenomena and superconducting-insulator transitions (SIT) for one-dimensional superconductors. We fabricated various nanowires with different widths and lengths from epitaxial NbTiN films using the electron beam lithography method. The temperature dependence of resistance R(T) below the superconducting transition temperature Tc was analyzed using thermal activation phase slip (TAPS) and quantum phase slip (QPS) theories. Although the accuracy of experimental data at low temperatures can deviate when using the TAPS model, the QPS model thoroughly represents the R(T) characteristic with resistive tail at low temperatures. From the analyses of data on Tc, we found that NbTiN nanowires exhibit SIT because of the change in the ratio of kinetic inductance energy and QPS amplitude energy with respect to the flux-charge duality theory.
Highlights
The state-of-the-art superconducting quantum computer consists of superconductor-insulator-superconductor tunnel junctions called Josephson junctions because it is a commonly used for superconducting digital circuits and quantum qubit for quantum computing devices
When the expression for the parallel case is approximately applied to superconducting nanowires (SNWs), it is expected that n approaches 1/2 with w ≈ξ(0)
We investigated the transport properties of superconducting niobium titanium nitride (NbTiN) SNWs in a wide range of RN/L using four-probe method to eliminate the contact resistance
Summary
The state-of-the-art superconducting quantum computer consists of superconductor-insulator-superconductor tunnel junctions called Josephson junctions because it is a commonly used for superconducting digital circuits and quantum qubit for quantum computing devices. In order to realize novel devices using nanowires, it is necessary to clarify the superconducting transport characteristics that depend on the disorder, wire length L, width w, and many other parameters In such low-dimensional superconductors, quantum effects slightly influence the superconducting characteristics. Mooij et al proposed an idea that the concept of flux-charge duality can relate the QPS with Josephson tunneling if the roles of phase and charge are interchanged[1] They discussed the crossover value between superconducting and insulating states at low temperatures as a function of ratio α =Es/EL, where Es and EL are the QPS energy and inductive energy, respectively. We analyzed the data from the superconducting and insulating phase diagrams based on the flux-charge duality model using the relation (RN/RQ)/(L/ξ) versus L/ξ with a suitable parameter α and other parameters in theories[1]
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