arXiv subjects
Publications and source records attributed to J. Zaanen.
It will be attempted to present a coherent view on the current ideas regarding the origin of the stripe instability. Special emphasis will be put on the problem of how to combine the microscopic pictures, leaning on spin-charge topological aspects, with the notion of frustrated phase separation.
The separation of the charge- and spin ordering temperatures of the stripe phase in cuprate superconductors has been used to argue that the striped phase is charge driven. Scaling analysis of a non-linear sigma model shows that the effect of spatial anisotropy on the transversal spin fluctuations is much more drastic at finite temperatures than at zero temperature. These results suggest that the spin fluctuations prohibit the spin system to condense at the charge ordering temperature, despite a possible dominance of charge-spin coupling in the longitudinal channel.
It is conjectured that the anomalous spin dynamics observed in the normal state of cuprate superconductors might find its origin in a nearly ordered spin system which is kept in motion by thermally meandering charged domain walls. `Temperature sets the scale' finds a natural explanation, while a crossover to a low temperature quantum domain wall fluid is implied.
The bilayer Heisenberg antiferromagnet is known to exhibit a quantum-critical transition at a particular value of the inter-layer coupling. Using a new type of coherent state, appropriate to the special order parameter structure of the bilayer, we map the problem onto the quantum non-linear sigma model. It is found that the bare coupling constant diverges at the classical transition of Chubukov and Morr, so that in any finite dimension the actual transition occurs inside the ordered phase of the classical theory.
The discovery by Tranquada et al. of an ordered phase of charged domain walls in the high-Tc cuprates leads us to consider the possible existence of a quantum domain-wall liquid. We propose minimal models for the quantization, by meandering fluctuations, of isolated charged domain walls. These correspond to lattice string models. The simplest model of this kind, a directed lattice string, can be mapped onto a quantum spin chain or on a classical two-dimensional solid-on-solid surface model. The model exhibits a rich phase diagram, containing several rough phases with low-lying excitations as well as ordered phases which are gapped.