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Quantum versus classical behavior in the boundary susceptibility of the ferromagnetic Heisenberg chain

J. Sirker·M. Bortz
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Abstract

We calculate the temperature dependence of the boundary susceptibility $χ_B$ for the quantum ferromagnetic Heisenberg chain by a modified spin-wave theory (MSWT). We find that $χ_B$ diverges at low temperatures $\sim -T^{-3}$ and therefore more rapidly and with opposite sign than the bulk susceptibility $χ_{\text{bulk}}\sim T^{-2}$. Our result for $χ_B$ is identical in leading order with the result for the classical system. In next leading orders, however, quantum corrections to the classical result exist which are important to obtain a good description over a wide temperature range. For the $S=1/2$ case, we show that our full result from MSWT is in excellent agreement with numerical data obtained by the density-matrix renormalization group applied to transfer matrices. Finally, we discuss the quantum to classical crossover as well as consequences of our results for experiment in some detail.

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J. Sirker, M. Bortz. 2005-09-07. Quantum versus classical behavior in the boundary susceptibility of the ferromagnetic Heisenberg chain. https://doi.org/10.1103/physrevb.73.014424

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