Quantum Brownian motion for magnets

  title={Quantum Brownian motion for magnets},
  author={Janet Anders and C R J Sait and Simon A. R. Horsley},
  journal={New Journal of Physics},
Spin precession in magnetic materials is commonly modelled with the classical phenomenological Landau–Lifshitz–Gilbert (LLG) equation. Based on a quantized three-dimensional spin + environment Hamiltonian, we here derive a spin operator equation of motion that describes precession and includes a general form of damping that consistently accounts for memory, coloured noise and quantum statistics. The LLG equation is recovered as its classical, Ohmic approximation. We further introduce resonant… 

Quantum Langevin Equation of a spin in a magnetic field : an analysis

We derive a quantum Langevin equation for a quantum spin in the presence of a magnetic field and study its dynamics in the Markovian limit using the Ohmic bath model. We extend our analysis to the

Quantum-classical correspondence in spin-boson equilibrium states at arbitrary coupling

It is known that the equilibrium properties of nanoscale systems can deviate significantly from standard thermodynamics due to their coupling to an environment. For the generalised θ -angled

Steady state in strong system-bath coupling regime: Reaction coordinate versus perturbative expansion.

Motivated by the growing importance of strong system-bath coupling in several branches of quantum information and related technological applications, we analyze and compare two strategies currently

Magnetization switching in the inertial regime

Kumar Neeraj, Matteo Pancaldi, ∗ Valentino Scalera, Salvatore Perna, Massimiliano d’Aquino, Claudio Serpico, and Stefano Bonetti 4, † Department of Physics, Stockholm University, 106 91 Stockholm,

Steady state in strong bath coupling: reaction coordinate versus perturbative expansion

Motivated by the growing importance of strong system-bath coupling in several branches of quantum information and related technological applications, we analyze and compare two strategies currently



Thermal Fluctuations of a Single-Domain Particle

A sufficiently fine ferromagnetic particle has a uniform vector magnetization whose magnitude is essentially constant, but whose direction fluctuates because of thermal agitation. The fluctuations

Path integral approach to quantum Brownian motion


Quantization of the electromagnetic field in dielectrics.

  • HuttnerBarnett
  • Physics
    Physical review. A, Atomic, molecular, and optical physics
  • 1992
The dielectric constant of the medium is explicitly derived and is shown to satisfy the Kramers-Kronig relations and the exact eigenoperators for the coupled system are calculated.

Magnetization dynamics in the inertial regime: Nutation predicted at short time scales

The dynamical equation for magnetization has been reconsidered by enlarging the phase space of the ferromagnetic degrees of freedom to the angular momentum. The generalized Landau-Lifshitz-Gilbert

Inertial spin dynamics in ferromagnets

The understanding of how spins move and can be manipulated at pico- and femtosecond timescales has implications for ultrafast and energy-efficient data-processing and storage applications. However,

Semiquantum thermodynamics of complex ferrimagnets

High-quality magnets such as yttrium iron garnet (YIG) are electrically insulating and very complex. By implementing a quantum thermostat into atomistic spin dynamics we compute YIG's key

Atomistic spin model simulations of magnetic nanomaterials

The key methods used in atomistic spin models are presented, which are then applied to a range of magnetic problems, and the parallelization strategies used enable the routine simulation of extended systems with full atomistic resolution.

Coupling function from bath density of states

Modelling of an open quantum system requires knowledge of parameters that specify how it couples to its environment. However, beyond relaxation rates, realistic parameters for specific environments

Spin-lattice dynamics model with angular momentum transfer for canonical and microcanonical ensembles

A unified model of molecular and atomistic spin dynamics is presented enabling simulations both in microcanonical and canonical ensembles without the necessity of additional phenomenological spin