Solving spin quantum-master equations with matrix continued-fraction methods: application to superparamagnets

Abstract

We implement continued-fraction techniques to solve exactly quantum master equations for a spin with arbitrary S coupled to a (bosonic) thermal bath. The full spin density matrix is obtained, so that along with relaxation and thermoactivation, coherent dynamics is included (precession, tunnel, etc.). The method is applied to study isotropic spins and spins in a bistable anisotropy potential (superparamagnets). We present examples of static response, the dynamical susceptibility including the contribution of the different relaxation modes, and of spin resonance in transverse fields.

Resubmitted to J. Phys. A: Math. Gen. Some rewriting here and there. Discussion on positivity in App.D3 at request of one referee

References in corpus (5)

• Caldeira--Leggett quantum master equation in Wigner phase space: continued-fraction solution and application to Brownian motion in periodic potentials
• Solving quantum master equations in phase space by continued-fraction methods
• Longitudinal relaxation and thermoactivation of quantum superparamagnets
• Spin dynamics in a dissipative environment: from quantal to classical
• Dynamics of Dissipative Quantum Systems--from Path Integrals to Master Equations

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• Equilibrium susceptibilities of superparamagnets: longitudinal & transverse, quantum & classical
• Spin relaxation in phase space
• Study of Classical and Quantum Open Systems
• Nonlinear ac stationary response and dynamic magnetic hysteresis of quantum uniaxial superparamagnets