Spectral flow of non-hermitian Heisenberg spin chain with complex twist

Non - linear Field Theory of a Frustrated Heisenberg Spin Chain

We derive a continuum field theory for the Majumdar-Ghosh model in the large-S limit, where the field takes values in the manifold of the SO(3) group. No topological term is induced in the action and the cases for integer spin and half-integer spin appear to be indistinguishable. A one-loop β−function calculation indicates that the theory flows towards a strong coupling (disordered) phase at lo...

Quantum spin transistor with a Heisenberg spin chain

Spin chains are paradigmatic systems for the studies of quantum phases and phase transitions, and for quantum information applications, including quantum computation and short-distance quantum communication. Here we propose and analyse a scheme for conditional state transfer in a Heisenberg XXZ spin chain which realizes a quantum spin transistor. In our scheme, the absence or presence of a cont...

Critical exponents of the Heisenberg spin chain.

PT Symmetry of the non-Hermitian XX Spin-Chain: Non-local Bulk Interaction from Complex Boundary Fields

The XX spin-chain with non-Hermitian diagonal boundary conditions is shown to be quasi-Hermitian for special values of the boundary parameters. This is proved by explicit construction of a new inner product employing a ”quasi-fermion” algebra in momentum space where creation and annihilation operators are not related via Hermitian conjugation. For a special example, when the boundary fields lie...

The Ising quantum spin chain in an imaginary field A spin chain model with non-Hermitian interaction: The Ising quantum spin chain in an imaginary field

We investigate a lattice version of the Yang-Lee model which is characterized by a non-Hermitian quantum spin chain Hamiltonian. We propose a new way to implement PT -symmetry on the lattice, which serves to guarantee the reality of the spectrum in certain regions of values of the coupling constants. In that region of unbroken PT -symmetry we construct a Dyson map, a metric operator and find th...