The influence of pinholes and weak-points in aluminium-oxide Josephson junctions
arXiv:2311.15560 · doi:10.1103/PhysRevMaterials.8.046202
Abstract
Josephson junctions are the key components used in superconducting qubits for quantum computing. The advancement of quantum computing is limited by a lack of stability and reproducibility of qubits which ultimately originates in the amorphous tunnel barrier of the Josephson junctions and other material imperfections. Pinholes in the junction have been suggested as one of the possible contributors to these instabilities, but evidence of their existence and the effect they might have on transport is unclear. We use molecular dynamics to create three-dimensional atomistic models to describe Al-AlOx-Al tunnel junctions, showing that pinholes form when oxidation of the barrier is incomplete. Following this we use the atomistic model and simulate the electronic transport properties for tunnel junctions with different barrier thicknesses using the non-equilibrium Green's function formalism. We observe that pinholes may contribute to excess quasiparticle current flow in Al-AlOx-Al tunnel junctions with thinner barriers, and in thicker barriers we observe weak-points which facilitate leakage currents even when the oxide is continuous. We find that the disordered nature of the amorphous barrier results in significant variations in the transport properties. Additionally, we determine the current-phase relationship for our atomistic structures, confirming that devices with pinholes and weak-points cause a deviation from the ideal sinusoidal Josephson relationship.
arXiv comment17 pages, 15 figures
References in corpus (29)
- Shot Noise in Mesoscopic Conductors
- Superconducting Qubits: Current State of Play
- Towards understanding two-level-systems in amorphous solids -- Insights from quantum circuits
- Exponential suppression of bit or phase flip errors with repetitive error correction
- Transmission eigenchannels from non-equilibrium Green's functions
- Efficient implementation of the nonequilibrium Green function method for electronic transport calculations
- Decoherence in Josephson-junction qubits due to critical current fluctuations
- Interacting two-level defects as sources of fluctuating high-frequency noise in superconducting circuits
- Improving wafer-scale Josephson junction resistance variation in superconducting quantum coherent circuits
- Conduction mechanisms in biphenyl-dithiol single-molecule junctions
- Simplified Josephson-junction fabrication process for reproducibly high-performance superconducting qubits
- Integrated tool-set for Control, Calibration and Characterization of quantum devices applied to superconducting qubits
- Observation of Josephson Harmonics in Tunnel Junctions
- Merged-Element Transmons: Design and Qubit Performance
- Are pinholes the cause of excess current in superconducting tunnel junctions? A study of Andreev current in highly resistive junctions
- Path toward manufacturable superconducting qubits with relaxation times exceeding 0.1 ms
- Microscopic Model of Critical Current Noise in Josephson Junctions
- Quantitative evaluation of defect-models in superconducting phase qubits
- Optimization of -Layer Systems for Josephson Junctions from a Microstructure Point of View
- Probing defect densities at the edges and inside Josephson junctions of superconducting qubits
- Supercurrent Interference in Semiconductor Nanowire Josephson Junctions
- Simulating the fabrication of aluminium oxide tunnel junctions
- Low frequency resistance and critical current fluctuations in Al-based Josephson junctions
- The effect of atomic structure on the electrical response of aluminium oxide tunnel junctions
- Electrical stress effect on Josephson tunneling through ultrathin AlOx barrier in Nb/Al/AlOx/Nb junctions
- High-speed calibration and characterization of superconducting quantum processors without qubit reset
- Coherent Josephson phase qubit with a single crystal silicon capacitor
- Sub-micrometer epitaxial Josephson junctions for quantum circuits
- Parity effect and single-electron injection for Josephson-junction chains deep in the insulating state