Periodic Reporting for period 1 - JOSEPHINE (HIGH-TC JOSEPHSON NEURONS AND SYNAPSES: TOWARDS ULTRAFAST AND ENERGY EFFICIENT SUPERCONDUCTING NEUROMORPHIC COMPUTING)
Période du rapport: 2024-05-01 au 2025-04-30
We aim at realizing a novel class of high-temperature Josephson junctions (JJs) that behave as artificial neurons and synapses. These JJs will enable a new neuromorphic computing paradigm, in which neural networks are much faster, more energy efficient and compact than with non-superconducting approaches, and possess novel capabilities (combined sensitivity to light, magnetic and electric fields).
Via these rupture ingredients, JOSEPHINE will dramatically enhance the impact of neuromorphics on its broad range of projected applications: from artificial intelligence (where it would allow supercomputer-level processors at a fraction of the environmental cost) to the control of autonomous vehicles, the Internet of Things, and novel medical applications. That constitutes the long-term vision for the science we propose. To reach that goal, we will use different strategies to realize high-Tc Josephson junctions whose weaklinks are active and can be changed "in operando" by external stimuli. Those strategies include "weak links" modified by a nanoscale redox reaction, by the motion of domain walls in a ferromagnet, or by locally doping a graphene or a 2D semiconductor. Once realized, these JJs will be implemented and tested in neural networks to demonstrate their performance and their transformative effect on neuromorphics. The proposed strategy exploits recent breakthrough results of the partners (physical effects that will be implemented) and synergizes their complementary expertise via a multidisciplinary approach that marries traditionally distant disciplines: neural network engineering, superconducting electronics, and various facets of solid-state physics (superconductivity, magnetism, Dirac materials, and electrochemistry).
Via these rupture ingredients, JOSEPHINE will dramatically enhance the impact of neuromorphics on its broad range of projected applications: from artificial intelligence (where it would allow supercomputer-level processors at a fraction of the environmental cost) to the control of autonomous vehicles, the Internet of Things, and novel medical applications. That constitutes the long-term vision for the science we propose. To reach that goal, we will use different strategies to realize high-Tc Josephson junctions whose weaklinks are active and can be changed "in operando" by external stimuli. Those strategies include "weak links" modified by a nanoscale redox reaction, by the motion of domain walls in a ferromagnet, or by locally doping a graphene or a 2D semiconductor. Once realized, these JJs will be implemented and tested in neural networks to demonstrate their performance and their transformative effect on neuromorphics. The proposed strategy exploits recent breakthrough results of the partners (physical effects that will be implemented) and synergizes their complementary expertise via a multidisciplinary approach that marries traditionally distant disciplines: neural network engineering, superconducting electronics, and various facets of solid-state physics (superconductivity, magnetism, Dirac materials, and electrochemistry).
During the first years of the action, the efforts are concentrated on developing high-temperature Josephson Junctions (JJs) that are sensitive either to electric fields, the history of current or magnetic pulses applied to them, or to optical stimuli. During the first Reporting Period:
- We have successfully demonstrated that planar JJs can be fabricated using a redox approach. Additionally, we have made significant progress in achieving Grooved Dayem Bridges tunable via current pulses.
- We realized a tunable magnetic structure in the half-metallic ferromagnetic LSMO, which will be used as a weak link in JJs. We have successfully demonstrated the continuous rotation of magnetization in the LSMO nanostructure, enabling magnetization switching with small magnetic fields. Initial theoretical modeling and support have begun through the development of a framework that combines quasiclassical kinetic equations with the Landau-Lifshitz-Gilbert equations, which describe magnetization dynamics.
- We have developed a versatile nano-fabrication approach that can be applied to combine YBCO and 2D materials in a variety of forms. This has required engineering and optimizing the device layout, developing the nano-lithography method, as well as implementing/optimizing the various 2D materials transfer techniques.
- We have performed optical characterization of hybrid structures of YBCO and Transition Metal Dichalcogenides. We have developed a novel ellipsometry approach to deal with ultrathin samples, a foundational capability essential for characterizing the high-TC JJs with 2D materials.
- We have submitted a patent on a novel JJ device, WO2025003423A1.
- We have successfully demonstrated that planar JJs can be fabricated using a redox approach. Additionally, we have made significant progress in achieving Grooved Dayem Bridges tunable via current pulses.
- We realized a tunable magnetic structure in the half-metallic ferromagnetic LSMO, which will be used as a weak link in JJs. We have successfully demonstrated the continuous rotation of magnetization in the LSMO nanostructure, enabling magnetization switching with small magnetic fields. Initial theoretical modeling and support have begun through the development of a framework that combines quasiclassical kinetic equations with the Landau-Lifshitz-Gilbert equations, which describe magnetization dynamics.
- We have developed a versatile nano-fabrication approach that can be applied to combine YBCO and 2D materials in a variety of forms. This has required engineering and optimizing the device layout, developing the nano-lithography method, as well as implementing/optimizing the various 2D materials transfer techniques.
- We have performed optical characterization of hybrid structures of YBCO and Transition Metal Dichalcogenides. We have developed a novel ellipsometry approach to deal with ultrathin samples, a foundational capability essential for characterizing the high-TC JJs with 2D materials.
- We have submitted a patent on a novel JJ device, WO2025003423A1.
1) The validation of the redox approach for the fabrication of JJs is a major advancement. The next steps include the demonstration of their tunability.
2) The control of the magnetic domain structure in the LSMO nanostructures is pivotal towards the goal of controlling Josephson coupling via the magnetic history.
3) The novel nanofabrication approach for combining cuprate superconductors and 2D materials has allowed the fabrication of a 1st generation of devices to test the transparency of the cuprate/2D material interface.
2) The control of the magnetic domain structure in the LSMO nanostructures is pivotal towards the goal of controlling Josephson coupling via the magnetic history.
3) The novel nanofabrication approach for combining cuprate superconductors and 2D materials has allowed the fabrication of a 1st generation of devices to test the transparency of the cuprate/2D material interface.