Quantum spintronics is an emerging field of spin coherence and spin correlations at or near room temperature, and their effects on a wide range of properties, including spin dynamics and light emission from color centers in solids, spin and charge transport in organic materials, spin-dependent transport in tunnel junctions, dynamic nuclear polarization, and animal sensing of magnetic fields. Room-temperature quantum spintronic systems can be much more sensitive to external perturbations than sensors that must be very near thermal equilibrium. Applications include sensing of magnetic fields in biological systems (e.g., color centers in diamond and other wide-bandgap semiconductors and insulators), control of light emission intensity from organic light-emitting diodes (e.g., thermally activated delayed fluorescence), spin injection, spin dynamics, and coherent optical interactions with single spins (color-center photonics). Highly sensitive room-temperature spin systems also feature prominently in proposals for very low power electronic logic.
This tutorial will provide an introduction to the materials and operating regimes that tend to exhibit room-temperature spin coherence and spin correlations, methods of calculating and measuring these properties, areas of initial application and critical open questions.
Theory of Quantum Spintronics
Michael E. Flatté, The University of Iowa
The theoretical criteria for a stable, room-temperature quantum coherent system will be described, and several examples will be presented. Methods of calculating the response of a quantum coherent system to external fields and perturbations will be presented, including density matrices, stochastic Liouville equations and master equations. Recent progress in predicting specific quantum coherent systems, such as density functional theory for new color centers in wide-gap semiconductors, will be surveyed. The ideal performance of quantum spintronic devices will be compared with other sensors or information processing approaches.
Quantum Magnonics and Magnonic Materials
Ezekiel Johnston-Halperin, The Ohio State University
Magnon excitations of magnetic materials are of increasing interest for quantum applications due to their broad spatial extent and their potential to efficient coupling to systems ranging from isolated single spins to microwave and optical photons. One of the central challenges in this field is the identification of materials with sufficiently low loss to support these emerging applications. Critical materials constraints and the current state of materials development will be presented.
3:00 pm BREAK
Optical Coupling to Quantum-Coherent Spins
David D. Awschalom, The University of Chicago
Coherent coupling of light to spin coherent systems, especially for color centers in diamond and silicon carbide, will be described in detail. Nonequilibrium polarization/pumping, manipulation of the spin state and efficient detection will be presented, along with criteria for pulse shaping that can be used for low-error manipulation of the spin state of a quantum coherent system.
Photonics and Quantum Spintronics
Evelyn Hu, Harvard University
The design, fabrication and measurement of photonic devices that efficiently integrate a quantum-coherent spin with a cavity will be described. Methods of manipulating the quantum spin to bring it into resonance with the cavity, such as through acoustic oscillations or electrical gates, will be presented. The figures of merit for spin-photon coupling will be derived and compared with state-of-the-art coupling of other quantum coherent systems.