Exactly Solvable Quasi-hermitian Transverse Ising Model
arXiv:0904.2852 · doi:10.1088/1751-8113/42/47/475208
Abstract
A non-hermitian deformation of the one-dimensional transverse Ising model is shown to have the property of quasi-hermiticity. The transverse Ising chain is obtained from the starting non-hermitian Hamiltonian through a similarity transformation. Consequently, both the models have identical eigen-spectra, although the eigen-functions are different. The metric in the Hilbert space, which makes the non-hermitian model unitary and ensures the completeness of states, has been constructed explicitly. Although the longitudinal correlation functions are identical for both the non-hermitian and the hermitian Ising models, the difference shows up in the transverse correlation functions, which have been calculated explicitly and are not always real. A proper set of hermitian spin operators in the Hilbert space of the non-hermitian Hamiltonian has been identified, in terms of which all the correlation functions of the non-hermitian Hamiltonian become real and identical to that of the standard transverse Ising model. Comments on the quantum phase transitions in the non-hermitian model have been made.
RevTeX 6 pages, no figures; Added discussions and references, version to appear in Journal of Physics A
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