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-band-gap 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 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 Spintronics of Organic Semiconductors
Organic semiconductors provide a varied set of materials that exhibit quantum spintronic phenomena. The effects of spin coherence on charge conductivity in organics will be described, along with large room-temperature responses to magnetic fields. Resonant manipulation of spins in organic materials, detected by transport, will be introduced as a mechanism for a sensitive magnetometer. Spin-charge correlations in the spin Hall Effect and spin pumping will also be presented.
3:00 pm BREAK
Quantum Information Processing with Spins
David D. Awschalom
Optical coupling of photons to spin coherent systems, especially for color centers in diamond and silicon carbide, will be described in detail. Nonequilibrium polarization/pumping, quantum manipulation of the spin states 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. Emerging methods to connect quantum states with magnons and phonons will also be discussed.
Photonics and Quantum Spintronics
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.
- Michael E. Flatté, The University of Iowa
- David D. Awschalom, The University of Chicago
- Christoph Boehme, The University of Utah
- Evelyn Hu, Harvard University