arXiv:1301.3538 · Physical Review B
Ordering and criticality in an underscreened Kondo chain
Wing-Ho Ko, Hong‐Chen Jiang, Jeffrey G. Rau, Leon Balents
Abstract
Motivated by the nickel valence controversy in the perovskite nickelate $R$NiO${}_{3}$, we consider a one-dimensional underscreened Kondo chain consisting of alternating spin-1 (``nickel'') and electron (``oxygen'') sites, which in addition to the usual electron hopping and spin-spin interaction between the $S=1$ spin and the electron also contains a spin-mediated electron hopping term. Using the density-matrix renormalization group (DMRG), we obtained the zero-temperature phase diagram of the model, as well as various correlation functions in each phase. Importantly, for a certain range of parameters the model exhibits a quasi-long-range spiral (QS) order. To understand the DMRG results, we construct a mean-field theory based on a Schwinger fermion decomposition of the $S=1$ spins, from which we argue that the QS phase corresponds to a phase in proximity to the spin Bose metal state proposed by Sheng, Motrunich, and Fisher [Phys. Rev. B 79, 205112 (2009)]. Notably, we find no evidence for a phase with the symmetry of ``nickel''-centered charge order, which has been argued to arise due to site-selective Kondo screening of half the $S=1$ spins, and suggest that order of this type occurs only due to an additional energy gain from spontaneous lattice distortions, not present in this model.