Spin Tunneling, Decoherence, and Collective Effects in Nanomagnetic Systems

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TECHNICAL SUMMARYThis award supports theoretical research and education in the field of quantum magnetism. Research is focused on collective quantum effects, entanglement and decoherence in nanomagnetic systems. The main thrusts include:1) Collective quantum effects in molecular magnets, such as propagating fronts of spin tunneling, electromagnetic and acoustic superradiance. The PIs will use the idea of self-organization of the dipolar field to study these systems. Self-organization provides a resonance condition for spin levels in a large volume of the crystal regardless of disorder. It can lead to coherent radiation of photons and phonons by a macroscopic number of magnetic molecules. A model of dipolar field self-organization recently developed by the PIs will be extended to describe this effect in bulk crystals of molecular magnets. The possibility of photon and phonon superradiance generated by propagating spin-tunneling fronts will be investigated. Theoretical and related experimental research will interact closely to investigate spin-tunneling fronts. 2) Coherent states and decoherence of spins coupled to mechanical nanoresonators. The PIs will study the entanglement and decoherence of spins by analytical and numerical methods within a fundamental microscopic model of spin-lattice interaction. The role of geometry will be elucidated and the effects of nuclear spins will be investigated. This research will address the quality factor of small resonators, as well as the prospect of using spins coupled to nanoresonators as qubits and ultra-sensitive magneto-mechanical probes. Entanglement of quantum spin states with coherent phonon states of an elastic solid, dictated by the conservation of angular momentum, will be investigated. This research will advance understanding of the limits of spin sensors and nanomechanical actuators, as well as the role of conservation laws in decoherence of spin-based qubits.Doctoral, undergraduate, and high-school students, including women and minorities, will be involved in the research. The Nanomagnetism Group at CUNY Lehman College collaborates with researchers in the U.S. and abroad, organizes workshops on nanomagnetism, and participates in the community outreach by maintaining contacts with local schools. Young researchers seeking careers in industry and academia will be trained in traditional and modern magnetism, as well computational methods. Students associated with the group will acquire cross-cultural experiences through international symposia organized by the Nanomagnetism Group.NON-TECHNICAL SUMMARYThis award supports theoretical research and education on magnetism with an emphasis on the role of quantum mechanical effects and on magnetic systems and magnetic phenomena which involve a length scale of the size of large molecules, nanomagnetic systems. It is focused on collective quantum effects and spin relaxation in nanomagnetic systems. The two main directions of the research are collective quantum effects in spin systems and quantum dynamics of nano-mechanical systems containing spins. Studies of collective acoustic and electromagnetic relaxation in molecular magnets will explore recent ideas of principal investigators on self-organized moving fronts of spin tunneling and relaxation. Analytical and numerical work, partially based on methods of laser physics, will be peformed to understand collective quantum effects in spin systems. This research may influence other areas of physics that deal with the two-level systems. It will help understand spin relaxation rates in paramagnets, as well as the prospect of obtaining coherent sub-Terahertz radiation from crystals of molecular magnets. Magnetic relaxation and decoherence due to spin-orbit effects in solids is among most fundamental, largely unsolved, problems of condensed matter theory. They are related to such important applications of spin physics as magnetic resonance, magnetic recording, spintronics, quantum computing, and nanomechanical actuators. Progress made in manufacturing and measurements of individual nanomagnets has ignited novel interest to this set of problems. They will be studied via analytical and numerical models involving realistic magneto-mechanical coupling that accounts for the conservation of the total angular momentum. Doctoral, undergraduate, and high-school students, including women and minorities, will be involved in the research. The Nanomagnetism Group at CUNY Lehman College collaborates with researchers in the U.S. and abroad, organizes workshops on nanomagnetism, and participates in the community outreach by maintaining contacts with local schools. Young researchers seeking careers in industry and academia will be trained in traditional and modern magnetism, as well computational methods. Students associated with the group will acquire cross-cultural experiences through international symposia organized by the Nanomagnetism Group.