arXiv:0911.4660 · Physical Review Letters
Parity Effects in the Scaling of Block Entanglement in Gapless Spin Chains
Pasquale Calabrese, Massimo Campostrini B, Fabian H. L. Eßler, Bernard Nienhuis
Abstract
We consider the R\'enyi $\ensuremath{\alpha}$ entropies for Luttinger liquids (LL). For large block lengths $\ensuremath{\ell}$, these are known to grow like $\mathrm{ln}\ensuremath{\ell}$. We show that there are subleading terms that oscillate with frequency $2{k}_{F}$ (the Fermi wave number of the LL) and exhibit a universal power-law decay with $\ensuremath{\ell}$. The new critical exponent is equal to $K/(2\ensuremath{\alpha})$, where $K$ is the LL parameter. We present numerical results for the anisotropic XXZ model and the full analytic solution for the free fermion (XX) point.