Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 65: Quantum-Critical Phenomena II

TT 65.3: Vortrag

Mittwoch, 14. März 2018, 15:30–15:45, HFT-FT 131

Exact solution of the spin-1/2 XXX chain with off-diagonal boundary fields — •Andreas Klümper and Dennis Wagner — Wuppertal University

The spin-1/2 Heisenberg chain with periodic boundary conditions is a seminal model of integrable resp. exactly solvable systems. It is known that the Heisenberg chain with arbitrary boundary fields is still integrable, but so far defied an explicit solution for the case of off-diagonal fields which break the U(1) symmetry. As the magnetization is no longer a good quantum number, the direct application of the Bethe ansatz fails.

Here we show how the problem can be solved by a set of non-linear integral equations (NLIEs). Instead of two NLIEs as in the case of the periodically closed chain, we find a set of three NLIEs from which the eigenvalues of the Hamiltonian can be obtained. Finally, we present results for the spectrum in the conformal limit.