Spintronic harvesting of ambient thermal fluctuations – SpinElec

To maintain energy security in the face of a changing global climate, renewable energy sources are tasked with replacing fossil fuel-based sources. All energy harvesting strategies studied thus far exhibit tradeoffs. Natural energy sources can reach power densities P=100mW/cm2 (solar irradiation on earth) but cannot operate 24/7. Energy scavenging of artificial sources when present (radio frequency, thermal gradients, vibrations...) is autonomous but limited by a 10^2-10^8 times lower power density. As areas of frontier research in energy, mesoscopic quantum thermodynamics (QTD) offer on-chip (i.e. applicative) solutions to harvest thermal gradient energy with fast (~10GHz) electronic engine strokes, but operate at very low temperature & below the Carnot limit. Atomic QTD at room temperature (RT) involving out-of-equilibrium quantum resources, such as coherent states & non-thermal baths, can exceed this limit but utilize slower (~10MHz) engine strokes & require auxiliary equipment, i.e. remain model experiments.

We propose in this resubmitted project SpinElec to research a spintronic implementation of QTD that, as an autonomous solid-state device, can 24/7 harvest the thermal fluctuations of ambient temperature to generate electricity. Our ‘spintronic engine’ concept efficiently combines the best of mesoscopic & atomic QTD using advantages inherent to spintronics. The engine’s design associates fully spin-polarized electrodes & paramagnetic centers acting as the thermal fluctuator. The resulting solid-state device deploys several quantum resources (squeezed bath, injection of quantum coherence, phase transition) to yield an engine whose ultrafast (~100GHz) heat & work strokes are, as a novelty & an engine asset, quantum correlated.

According to the project’s IPCMS-IJL-IC partners’ joint experiments, this appears to enable the device to generate output power without a nominal temperature gradient. The partners implemented this spintronic engine using an industrially mature device platform: the MgO magnetic tunnel junction (MTJ), with a potential P 3x greater than solar irradiation. One difficulty, which the partners have worked on previously (ANR Spinapse), is to control the barrier oxygen vacancies that host the PM centers. To circumvent this issue, the IPCMS-IJL-IC partners have also studied a CoPc molecular implementation, which yields more working devices, 270x more output power at RT & evidence of the CoPc phase transition of magnetic fluctuations as another quantum resource.

We will investigate the fundamental tenets of the spintronic engine using the CoPc materials track: monitoring heat flow; tuning the heat/work strokes. To do so, we will confirm monolayer control over the device’s active molecular layers, improve our molecule-compatible vertical nanojunction process, & integrate on-chip thermometers. Theoretical partner LPMMC will develop an out-of-equilibrium QTD model of the spintronic engine that captures phase transition properties.

To achieve reproducible spintronic thermal harvesting using the more technologically mature MgO materials track, we will master the insertion of PM centers in MgO thanks to local probe & electronic paramagnetic resonance studies. We will utilize both materials tracks to develop a demonstrator to present to the IPCMS’s industrial strategy counselor IMEC, in order to jumpstart academic & industrial R&D efforts.

Project success would not only expose the QTD community to a new spintronic implementation of QTD, but generate a compelling Information & Communication (ICT) + energy dual-use to the MTJ. This would channel industrial companies traditionally focused on ICT (e.g. Canon-Anelva) into the renewable energy sector. These aspects make project SpinElec very original & innovative within energy research, & very disruptive within QTD & spintronics research. This research track can provide a potentially game-changing, innovative energy technology to help limit climate catastrophe.