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arXiv:2004.11371 · Modern Physics Letters B

Threshold singularities in the XXZ-spin chain

Alexander A. Ovchinnikov

Published Oct 14, 2020• 1 citation
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Abstract

We calculate the critical exponents of the threshold singularity for the spectral density of the XXZ-spin chain at zero magnetic field for the lower threshold. We show that the corresponding phase shifts are momentum independent and coincide with predictions of the effective mobile impurity Hamiltonian approach.
DOI
10.1142/s0217984921500445

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Transition rates and dynamic spin structure factor at zero temperature for the spin-1/2 XXZ chain at critical regime in a magnetic field are numerically evaluated in terms of the exact determinant representations for the form factors and norms of the Bethe eigenstates. We have seen that the transition rates converges toward the constant function with the value 1 in the limit delta -> 0. The observed critical exponent of the singularity at the lower boundary is compared with the one predicted from the comformal field theory. We confirm that they are in good agreement. Further we have discovered that a small peak emerges near the upper boundary in the line shape of S(q,omega) for 0
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