Oleg Derzhko
Institute for Condensed Matter Physics of the
National Academy of Sciences of Ukraine, L’viv Ukraine

We consider a deformable spin-1/2 antiferromagnetic XXZ Heisenberg chain and examine the spin-chain lattice compressibility as well as the sound velocity as a function of an external magnetic field applied either along the z axis or along the x axis. For strong fields, we observe a noticeable increase (with jump and hysteresis) of the lattice compressibility. Our findings are obtained by several complimentary approaches (Jordan-Wigner fermionization method, exact diagonalizations, and density matrix renormalization group technique). The lattice compressibility is related to the sound velocity which is accessible in acoustic experiments.

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