Magnetic and quantum entanglement properties of the distorted diamond chain model for azurite

We present the results of magnetic properties and entanglement of the distorted diamond chain model for azurite using pure quantum exchange interactions. The magnetic properties and concurrence as a measure of pairwise thermal entanglement have been studied by means of variational mean-field like treatment based on Gibbs-Bogoliubov inequality. Such a system can be considered as an approximation of the natural material azurite, Cu3(CO3)2(OH)2. For values of exchange parameters, which are taken from experimental results, we study the thermodynamic properties, such as azurite specific heat and magnetic susceptibility. We also have studied the thermal entanglement properties and magnetization plateau of the distorted diamond chain model for azurite

Interplay of magnetization dynamics with a microwave waveguide at cryogenic temperatures

In this work, magnetization dynamics is studied at low temperatures in a hybrid system that consists of a thin epitaxial magnetic film coupled with a superconducting planar microwave waveguide. The resonance spectrum was observed over a wide magnetic field range, including low fields below the saturation magnetization and both polarities. Analysis of the spectrum via a fitting routine we develop allows the derivation of all magnetic parameters of the film at cryogenic temperatures, the detection of waveguide-induced uniaxial magnetic anisotropies of the first and the second order, and the uncovering of a minor misalignment of the magnetic field. A substantial influence of the superconducting critical state on the resonance spectrum is observed and discussed

New type of self-oscillating systems

The time evolution of occupation number is studied for a bosonic oscillator (with one and two degrees of freedom) linearly fully coupled to fermionic and bosonic heat baths. The absence of equilibrium in this oscillator is discussed as a tool to create a dynamical non-stationary memory storage. The connection between such a system and the well-known nonlinear self-oscillating systems is demonstrated

Non-Markovian dynamics of mixed fermionic–bosonic systems: Full coupling

International audienceEmploying the quadratic fermionic and bosonic Hamiltonians for the collective and internal subsystems with a linear full coupling, we studied the role of heat-bath statistics on the dynamics of the collective motion. The master-equations for the collective occupation number derived directly within Non-Markovian Langevin approach are discussed and their solutions are obtained. As shown in the numerical calculations, the path to equilibrium or the relaxation time is affected by the heat-bath statistics and to the coupling type

Non-Markovian modeling of Fermi-Bose systems coupled to one or several Fermi-Bose thermal baths

International audienceA method is proposed to describe Fermi or Bose systems coupled to one or several heat baths composed of fermions and/or bosons. The method, called the coupled equations of motion method, properly includes non-Markovian effects. The approach is exact in the full-coupling approximation when only bosonic particles are present in the system and baths. The approach provides an approximate treatment when fermions are present either in the system and/or in one or several environments. Our approach has the advantage of properly respecting the Pauli exclusion principle for fermions during the evolution. We illustrate the approach for the single fermionic or bosonic oscillator coupled to one or two heat baths assuming different types of quantum statistics (fermion or boson) for them. The cases of a Fermi system coupled to fermion or boson heat baths or a mixture of both are analyzed in detail. With the future goal of treating Fermi systems formed of an increasing number of two-level systems (qubits), we discuss possible simplifications that could be made in the equations of motion and their limits of validity in terms of the system-bath coupling or of the initial heat bath temperatures

Non-Markovian dynamics of quantum systems coupled with several mixed fermionic-bosonic heat baths

International audienceFor the fermionic or bosonic oscillator fully coupled to several heat baths with mixed statistics, the analytical expressions for the occupation numbers are derived within the non-Markovian quantum Langevin approach. Employing two or three heat baths and the Ohmic dissipation with Lorenzian cutoffs, the role of statistics of the system and heat baths in the dynamics of the system is studied

Asymptotic equilibrium in quantum system fully coupled simultaneously to mixed fermionic–bosonic heat baths

International audienceThe full coupling of a quantum system to a heat bath usually induces its evolution towards an asymptotic equilibrium imposed by the complexity of the heat bath. We show here that such equilibrium might never be reached when the system is coupled simultaneously to bosonic and fermionic heat baths unless different thermal reservoirs are related with each others. Conditions under which an asymptotic equilibrium can be reached are discussed

Non-Markovian dynamics of fermionic and bosonic systems coupled to several heat baths

International audienceEmploying the fermionic and bosonic Hamiltonians for the collective oscillator linearly FC-coupled with several heat baths, the analytical expressions for the collective occupation number are derived within the non-Markovian quantum Langevin approach. The master equations for the occupation number of collective subsystem are derived and discussed. In the case of Ohmic dissipation with Lorenzian cutoffs, the possibility of reduction of the system with several heat baths to the system with one heat bath is analytically demonstrated. For the fermionic and bosonic systems, a comparative analysis is performed between the collective subsystem coupled to two heat baths and the reference case of the subsystem coupled to one bath

Applicability of the absence of equilibrium in quantum system fully coupled to several fermionic and bosonic heat baths

International audienceThe time evolution of an occupation number is studied for a fermionic or bosonic oscillator linearly fully coupled to several fermionic and bosonic heat baths. The influence of the characteristics of thermal reservoirs of different statistics on the nonstationary population probability is analyzed at large times. Applications of the absence of equilibrium in such systems for creating a dynamic (nonstationary) memory storage are discussed