相关论文: Quantum Thermoactivation of Nanoscale Magnets

The relaxation mechanisms of a quantum nanomagnet are discussed in the frame of linear response theory. We use a spin Hamiltonian with a uniaxial potential barrier plus a Zeeman term. The spin, having arbitrary $S$, is coupled to a bosonic…

The pulse-noise approach to systems of classical spins weakly interacting with the bath has been applied to study thermally-activated escape of magnetic nanoparticles over the uniform and nonuniform energy barriers at intermediate and low…

We derive a simple system of equations to describe the magnetization relaxation of a molecular spin in weak interaction with a thermal bath for the whole temperature domain. Using this for the intermediate temperature domain where the…

We propose and demonstrate an experimental scheme to engineer thermal baths with independently tunable temperatures and dissipation rates for the motional modes of a trapped-ion system. This approach enables robust thermal-state preparation…

We calculate the magnetisation relaxation in the short-time regime for an ensemble of nanomagnets in the presence of a low-frequency external AC biasing field, at temperatures lower than the magnetic anisotropy energy of the individual…

A new experimental procedure is discussed, which aims at separating thermal from quantum behavior independently of the energy barrier distribution in small particle systems. Magnetization relaxation data measured between 60 mK and 5 K on a…

The low temperature magnetization process of the ferromagnetic-antiferromagnetic Heisenberg chain is studied using the interacting boson approximation. In the low field regime and near the saturation field, the spin wave excitations are…

We examine the quantum tunneling of magnetization in molecular spin in weak interaction with a bath subject to Redfield master equation. By designing a microscopic model for a multilevel spin system using only a generic Hamiltonian and…

We provide a versatile analytical framework for calculating the dynamics of a spin system in contact with a fermionic bath beyond the Markov approximation. The approach is based on a second order expansion of the Nakajima-Zwanzig master…

We consider multiple non-interacting quantum mechanical two-level systems coupled to a common bosonic bath and study its quantum phase transition with Monte Carlo simulations using a continuous imaginary time cluster algorithm. The common…

At finite temperature we study the quantum tunneling of magnetization for a small ferromagnetic particle with the biaxial symmetry placed in a magnetic field at an arbitrary angle. We present numerical WKB exponent below the crossover…

The degree of contact between a system and the external environment can alter dramatically its proclivity to quantum mechanical modes of relaxation. We show that controlling the thermal coupling of cubic centimeter-sized crystals of the…

We have studied spin relaxation in the spin ice compound Dy2Ti2O7 through measurements of the a.c. magnetic susceptibility. While the characteristic spin relaxation time is thermally activated at high temperatures, it becomes almost…

We propose a systematic way to investigate the low-temperature thermodynamic properties of quantum spin systems subject to the restriction that only a finite number of bosons may occupy a single lattice site. Such a kinematical interaction…

We report an anomalous decoherence phenomenon of a quantum dissipative system in the framework of a stochastic decoupling scheme along with a hierarchical equations-of-motion formalism without the usual Born-Markov or weak coupling…

An exact reduced dynamical map along with its operator sum representation is derived for a central spin interacting with a thermal spin environment. The dynamics of the central spin shows high sustainability of quantum traits such as…

The asymptotic behavior of switching time as a function of current for a uniaxial macrospin under the effects of both spin-torque and thermal noise is explored analytically by focusing on its diffusive energy space dynamics. The scaling…

We study the effect of coupling a spin bath environment to a system which, at low energies, can be modeled as a quantum Ising system. A field theoretic formalism incorporating both thermal and quantum fluctuations is developed to derive…

The escape rate \Gamma of the large-spin model described by the Hamiltonian H = -DS_z^2 - H_zS_z - H_xS_x is investigated with the help of the mapping onto a particle moving in a double-well potential U(x). The transition-state method…

We have measured the relaxation time of a thermally unstable ferromagnetic nanoparticle incorporated into a magnetic tunnel junction (MTJ) as a function of applied magnetic field, voltage V (-0.38 V < V < +0.26 V), and temperatures (283 K<…