Related papers: On the partial trace over collective spin-degrees …
Electron pairing and ferromagnetism in various cluster geometries are studied with emphasis on tetrahedron and square pyramid under variation of interaction strength, electron doping and temperature. These exact calculations of charge and…
We compute the exact partition function of the 2D Ising Model at critical temperature but with nonzero magnetic field at the boundary. The model describes a renormalization group flow between the free and fixed conformal boundary conditions…
The physical properties of magnetic nanoparticles have been investigated with focus on the influence of dipolar interparticle interaction. For weakly coupled nanoparticles, thermodynamic perturbation theory is employed to derive analytical…
We study the low-temperature phase of the three-dimensional $\pm J$ Ising spin glass in Migdal-Kadanoff approximation. At zero temperature, T=0, the properties of the spin glass result from the ground-state degeneracy and can be elucidated…
We apply the modified spin-wave theory with the constraint of zero staggered magnetization to investigate normal-state spectral and magnetic properties of the 2D t-J model in the paramagnetic state. A set of self-energy equations for hole…
The relationship between thermodynamics and statistical physics is valid in the thermodynamic limit - when the number of particles becomes very large. Here, we study thermodynamics in the opposite regime - at both the nano scale, and when…
Geometrically frustrated interactions may render classical ground-states macroscopically degenerate. The connection between classical and quantum liquids and how the degeneracy is affected by quantum fluctuations is, however, less well…
We study the superradiance dynamics in a dense system of atoms each of which can be generally a spin-$j$ particle with $j$ an arbitrary half-integer. We generalize Dicke's superradiance point of view to multiple-level systems, and compare…
We calculate the rate of decrease of the expectation value of the transverse component of spin for spin-1/2 particles in a magnetic field with a spatial gradient, to determine the conditions under which a previous classical description is…
Using quantum Monte Carlo and numerical analytic continuation methods, we study the dynamic spin structure factor and the single-hole spectral function of a two-dimensional quantum magnet ($J$-$Q$ model) at its quantum phase transition…
Fractionalization remains one of the most fascinating manifestations of strong interactions in quantum many-body systems. In quantum magnetism, the existence of spinons -- collective magnetic excitations that behave as quasiparticles with…
We numerically study the dynamics and stationary states of a spin ensemble strongly coupled to a single-mode resonator subjected to loss and external driving. Employing a generalized cumulant expansion approach we analyze finite-size…
Decoherence originates from the leakage of quantum information into external degrees of freedom. For a qubit the two main decoherence channels are relaxation and dephasing. Here, we report an experiment on a superconducting qubit where we…
We investigate nonequilibrium phenomena in magnetic nano-junctions using a numerical approach that combines classical spin dynamics with the hierarchical equations of motion technique for quantum dynamics of conduction electrons. Our focus…
This paper focuses on the isospin properties of the asymmetric nuclear-matter liquid-gas phase transition analyzed in a mean-field approach, using Skyrme effective interactions. We compare two different mechanisms of phase separation for…
We investigate quantum correlations of the $N$-qubit states via a collective pseudo-spin interaction ($\propto J_y^2$) on arbitrary pure separable states for a given interval of time. Based on this dynamical generation of the $N$-qubit…
We prove a theorem that shows the degeneracy of many-body states depends on total particle number and flux filling ratio, for particles in a periodic lattice and under a uniform magnetic field. Non-interacting fermions and weakly…
The thermodynamic interaction at thermodynamic equilibrium in the free fermion gas is alternatively described by the coupling of particles with a scalar thermodynamic field which features a self-interaction. The gauge fields in $SU_c(3)$…
Various features of spin-polarized Fermi gases confined in harmonic traps are discussed, taking into account possible perspectives of experimental measurements. The mechanism of the expansion of the gas is explicitly investigated and…
The elementary excitations of a model Hamiltonian that captures the low energy behavior of a simple two-fold degenerate Hubbard Hamiltonian with Hund's rule coupling, is studied. The phase diagram in the mean-field limit and in a two-site…