Microwave-free dynamic nuclear polarization via sudden thermal jumps

Abstract

Dynamic Nuclear Polarization (DNP) presently stands as the preferred strategy to enhance the sensitivity of nuclear magnetic resonance measurements, but its application relies on the use of high-frequency microwave to manipulate electron spins, an increasingly demanding task as the applied magnetic field grows. Here we investigate the dynamics of a system hosting a polarizing agent formed by two distinct paramagnetic centers near a level anti-crossing. We theoretically show that nuclear spins polarize efficiently under a cyclic protocol that combines alternating thermal jumps and radio-frequency pulses connecting hybrid states with opposite nuclear and electronic spin alignment. Central to this process is the difference between the spin-lattice relaxation times of either electron spin species, transiently driving the electronic spin bath out of equilibrium after each thermal jump. Without the need for microwave excitation, this route to enhanced nuclear polarization may prove convenient, particularly if the polarizing agent is designed to feature electronic level anti-crossings at high magnetic fields.

References in corpus (4)

• Dynamic polarization of single nuclear spins by optical pumping of NV color centers in diamond at room temperature
• Quenching Spin Decoherence in Diamond through Spin Bath Polarization
• Two-electron-spin ratchets as a platform for microwave-free dynamic nuclear polarization of arbitrary material targets
• Nuclear spin temperature reversal via continuous radio-frequency driving