Topological defects in Spin Density Waves

The rich order parameter of Spin Density Waves allows for an unusual object of a complex topological nature: a half-integer dislocation combined with a semi-vortex of the staggered magnetization. It becomes energetically preferable to ordinary dislocation due to enhanced Coulomb interactions in the semiconducting regime. Generation of these objects changes e.g. the narrow band noise frequency. Topological defects in Electronic Crystals-solitons, phase slips (PS) and dislocation lines/loops (DLs) are ultimately necessary for the current conversion and depining processes, see collections [1, 2, 3]. Microscopically in Charge and Spin Density Waves (CDW, SDW, DW) the PS starts as a self-trapping of electrons into solitons with their subsequent aggregation (see [4, 5, 6] for review). Macroscopically the PS develops as the edge DL prolif-erating/expanding across the sample [8, 7]. An important feature of semiconducting quasi one-dimensional DWs is the Coulomb hardening [9] of their compressibility when the normal carriers freeze out at low temperature T. Then the energetics of DL [10], the accompanying electronic structure [11], etc. are determined by the Coulomb forces limited by screening facilities of remnant free carriers. The CDW/SDW are characterized by scalar/vector order parameters: η cdw ∼ cos[Qx + ϕ], η sdw ∼ m cos[Qx + ϕ] where m is the unit vector of the staggered magnetization. Here we will show that SDWs allow for unusual π PSs forbidden in CDWs where only 2π PSs are allowed. Namely in SDW conventional dislocations loose their priority in favor of special topological objects: a half-integer dislocation combined with a semi-vortex of a staggered magnetization vector. Their possible manifestation may be found in a Narrow band Noise (NBN) generation. The π-PSs reduce twice (down to its CDW value Ω/j = π) the universal ratio Ω/j of the fundamental NBN