arXiv:1108.6064 · Physical Review B
Quantum criticality of dipolar spin chains
Aldo Isidori, Annika Ruppel, Andreas Kreisel, Peter Kopietz, Alexander Mai, R. M. Noack
Abstract
We show that a chain of Heisenberg spins interacting with long-range dipolar forces in a magnetic field $h$ perpendicular to the chain exhibits a quantum critical point belonging to the two-dimensional Ising universality class. Within linear spin-wave theory, the magnon dispersion for small momenta $k$ is ${[{\ensuremath{\Delta}}^{2}+{v}_{k}^{2}{k}^{2}]}^{1/2}$, where ${\ensuremath{\Delta}}^{2}\ensuremath{\propto}|h\ensuremath{-}{h}_{c}|$ and ${v}_{k}^{2}\ensuremath{\propto}|\phantom{\rule{-0.16em}{0ex}}\mathrm{ln}k|$. For fields close to ${h}_{c}$ linear spin-wave theory breaks down, and we investigate the system using density-matrix and functional renormalization group methods. The Ginzburg regime where non-Gaussian fluctuations are important is found to be rather narrow on the ordered side of the transition and very broad on the disordered side.