Efimov effect in quantum magnets

Physics is said to be universal when it emerges regardless of the underlying microscopic details. A prominent example is the Efimov effect, which predicts the emergence of an infinite tower of three-body bound states obeying discrete scale invariance when the particles interact resonantly. Because of its universality and peculiarity, the Efimov effect has been the subject of extensive research in chemical, atomic, nuclear and particle physics for decades. Here we employ an anisotropic Heisenberg model to show that collective excitations in quantum magnets (magnons) also exhibit the Efimov effect. We locate anisotropy-induced two-magnon resonances, compute binding energies of three magnons and find that they fit into the universal scaling law. We propose several approaches to experimentally realize the Efimov effect in quantum magnets, where the emergent Efimov states of magnons can be observed with commonly used spectroscopic measurements. Our study thus opens up new avenues for universal few-body physics in condensed matter systems.Comment: 7 pages, 5 figures; published versio

Some magnetic properties of the pseudo one-dimensional Ising-like magnetic systems CsCoCl3·2H2O and RbFeCl3·2H2O

\u3cp\u3eThe heat capacity of CsCoCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO and RbFeCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO has been analyzed using a d = 1 and d = 2 Ising model, respectively, yielding |J/k| = 38.6K for CsCOCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO and |J/k| = 39 K, |J/k| = 0.7 K for RbFeCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO. RbFeCl\u3csub\u3e3\u3c/sub\u3e·2H\u3csub\u3e2\u3c/sub\u3eO shows two metamagnetic transitions in applied fields along the c axis.\u3c/p\u3