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Graham Kimbell

Publications and source records attributed to Graham Kimbell.

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Accelerating discovery across scientific disciplines through reproducible workflows with AiiDAlab

With ever-increasing computational capabilities, robust and automated research workflows have become essential for orchestrating large numbers of interdependent simulations. However, significant technical expertise is still required to configure execution environments, define calculation inputs, interpret outputs, and manage the complexity of parallel code execution on remote machines. To address these challenges, we developed AiiDAlab, a Jupyter-based web platform powered by the AiiDA computational infrastructure that provides a framework for managing and automating computational workflows while ensuring reproducibility through full provenance tracking. Through a collection of open-source user-friendly applications, AiiDAlab enables scientists to set up, execute, and analyze complex computational workflows without interacting directly with the underlying technical details, allowing them to focus on their research questions. In this paper, we discuss how AiiDAlab has matured over the past few years, expanding beyond computational materials science and its AiiDA origins. We present recent developments towards integrating with electronic laboratory notebooks (ELNs) for FAIR-compliant data management, adoption in large-scale facilities for secure access to experimental data and analytical tools, and applications in educational settings. Together with community-driven efforts to simplify onboarding, improve access to computational resources, and support large-scale data workflows, these advancements position AiiDAlab as a powerful platform for accelerating scientific discovery and fostering collaboration across disciplines.

cs.DC

Electric field control of superconducting fluctuations and quasiparticle interference at oxide interfaces

We investigate tunable superconducting transitions in (111)$\mathrm{LaAlO}_3/\mathrm{KTaO}_3$ field-effect devices. Large increases in conductivity, associated with superconducting fluctuations, are observed far above the transition temperature. However, the standard Aslamazov-Larkin paraconductivity model significantly underestimates the effect observed here. We use a model that includes conductivity corrections from normal state quasiparticle interference together with all contributions from superconducting fluctuations evaluated at arbitrary temperatures and in the short-wavelength limit. Through analysis of the magnetoconductance and resistive transitions, we find that the large conductivity increase can be explained by a combination of weak anti-localization and Maki-Thompson superconducting fluctuations. Both contributions are enabled by a strong temperature dependence of the electron's decoherence time compatible with an electron-phonon scattering scenario. We find that conductivity corrections are modulated by the electrostatic field effect, that governs a competition between normal-state quasiparticle interference and superconducting fluctuations.

cond-mat.supr-con

High-field superconductivity from atomic-scale confinement and spin-orbit coupling at (111)$\mathrm{LaAlO_3/KTaO_3}$ interfaces

We study the superconducting critical fields of two-dimensional electron systems at (111)$\mathrm{LaAlO_3/KTaO_3}$ interfaces as a function of electrostatic back-gating. Our work reveals inplane critical fields of unprecedented magnitudes at oxide interfaces. By comparing the critical fields in-plane and out-of-plane we discover an extremely anisotropic superconductor with an effective thickness below 1 nm and a 12-fold violation of the Chandrasekhar-Clogston paramagnetic limit. The analysis of magneto-transport indicates that the enhancement of the critical fields is due to an exceptionally thin superconducting layer and to a paramagnetic susceptibility suppressed by spin-orbit scattering.

cond-mat.supr-con

Thermal annealing enhancement of Josephson critical currents in ferromagnetic CoFeB

The electrical and structural properties of Co40Fe40B20 (CoFeB) alloy are tunable with thermal annealing. This is key in the optimization of CoFeB-based spintronic devices, where the advantageously low magnetic coercivity, high spin polarization, and controllable magnetocrystalline anisotropy are utilised. So far, there has been no report on superconducting devices based on CoFeB. Here, we report Nb/CoFeB/Nb Josephson devices and demonstrate an enhancement of the critical current by up to 700% following thermal annealing due to increased structural ordering of the CoFeB. The results demonstrate that CoFeB is a promising material for the development of superconducting spintronic devices.

cond-mat.supr-con

Two-channel anomalous Hall effect in SrRuO3

The Hall effect in SrRuO$_3$ thin-films near the thickness limit for ferromagnetism shows an extra peak in addition to the ordinary and anomalous Hall effects. This extra peak has been attributed to a topological Hall effect due to two-dimensional skyrmions in the film around the coercive field; however, the sign of the anomalous Hall effect in SrRuO$_3$ can change as a function of saturation magnetization. Here we report Hall peaks in SrRuO$_3$ in which volumetric magnetometry measurements and magnetic force microscopy indicate that the peaks result from the superposition of two anomalous Hall channels with opposite sign. These channels likely form due to thickness variations in SrRuO$_3$, creating two spatially separated magnetic regions with different saturation magnetizations and coercive fields. The results are central to the development of strongly correlated materials for spintronics.

cond-mat.str-el