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We consider the two-spin subsystem entanglement for eigenstates of the Hamiltonian [ H= sum_{1leq j< k leq N} (frac{1}{r_{j,k}})^{alpha} {mathbf sigma}_jcdot {mathbf sigma}_k ] for a ring of $N$ spins 1/2 with asssociated spin vector operator $(hbar /2){bf sigma}_j$ for the $j$-th spin. Here $r_{j,k}$ is the chord-distance betwen sites $j$ and $k$. The case $alpha =2$ corresponds to the solvable Haldane-Shastry model whose spectrum has very high degeneracies not present for $alpha eq 2$. Two spin subsystem entanglement shows high sensistivity and distinguishes $alpha =2$ from $alpha eq 2$. There is no entanglement beyond nearest neighbors for all eigenstates when $alpha =2$. Whereas for $alpha eq 2$ one has selective entanglement at any distance for eigenstates of sufficiently high energy in a certain interval of $alpha$ which depends on the energy. The ground state (which is a singlet only for even $N$) does not have entanglement beyond nearest neighbors, and the nearest neighbor entanglement is virtually independent of the range of the interaction controlled by $alpha$.
In this study, considering the long-range interaction with an inverse-square and its trigonometric and hyperbolic variants in SCM model we investigate entanglement in (1/2,1) mixed-spin XY model. We also discuss the temperature and magnetic field dep
We investigate many-body spin squeezing dynamics in an XXZ model with interactions that fall off with distance $r$ as $1/r^alpha$ in $D=2$ and $3$ spatial dimensions. In stark contrast to the Ising model, we find a broad parameter regime where spin s
We examine the concurrence and entanglement entropy in quantum spin chains with random long-range couplings, spatially decaying with a power-law exponent $alpha$. Using the strong disorder renormalization group (SDRG) technique, we find by analytical
Unparticles as suggested by Georgi are identities that are not constrained by dispersion relations but are governed by their scaling dimension, d. Their coupling to particles can result in macroscopic interactions between matter, that are generally a
We investigate the entanglement properties of the Kondo spin chain when it is prepared in its ground state as well as its dynamics following a single bond quench. We show that a true measure of entanglement such as negativity enables to characterize