Conformally invariant free-parafermionic quantum chains with multispin interactions.

We calculate the spectral properties of two related families of non-Hermitian free-particle quantum chains with N-multispin interactions (N=2,3,...

Free-parafermionic Z(N) and free-fermionic XY quantum chains.

The relationship between the eigenspectrum of Ising and XY quantum chains is well known. Although the Ising model has a Z(2) symmetry and the XY model a U(1) symmetry, both models are described in terms of free-fermionic quasiparticles. The fermionic quasienergies are obtained by means of a Jordan-Wigner transformation.

Anomalous bulk behavior in the free parafermion Z(N) spin chain.

We demonstrate using direct numerical diagonalization and extrapolation methods that boundary conditions have a profound effect on the bulk properties of a simple Z(N) model for N≥3 for which the model Hamiltonian is non-Hermitian. For N=2 the model reduces to the well-known quantum Ising model in a transverse field. For open boundary conditions, the Z(N) model is known to be solved exactly in terms of free parafermions.

Entanglement of low-energy excitations in conformal field theory.

In a quantum critical chain, the scaling regime of the energy and momentum of the ground state and low-lying excitations are described by conformal field theory (CFT). The same holds true for the von Neumann and Rényi entropies of the ground state, which display a universal logarithmic behavior depending on the central charge. In this Letter we generalize this result to those excited states of the chain that correspond to primary fields in CFT.

Exactly solvable interacting spin-ice vertex model.

A special family of solvable five-vertex model is introduced on a square lattice. In addition to the usual nearest-neighbor interactions, the vertices defining the model also interact along one of the diagonals of the lattice. This family of models includes in a special limit the standard six-vertex model.

Anomalous tag diffusion in the asymmetric exclusion model with particles of arbitrary sizes.

Anomalous behavior of correlation functions of tagged particles are studied in generalizations of the one-dimensional asymmetric exclusion problem. In these generalized models the range of the hard-core interactions are changed and the restriction of relative ordering of the particles is partially broken. The models probing these effects are those of biased diffusion of particles having size S=0,1,2, em leader, or an effective negative "size" S=-1,-2, em leader, in units of lattice space.