Current jumps in flat-band ladders with Dzyaloshinskii-Moriya interactions

Abstract

Localized magnons states, due to flat bands in the spectrum, is an intensely studied phenomenon and can be found in many frustrated magnets of different spatial dimensionality. The presence of Dzyaloshinskii-Moriya (DM) interactions may change radically the behavior in such systems. In this context, we study a paradigmatic example of a one-dimensional frustrated antiferromagnet, the sawtooth chain in the presence of DM interactions. Using both path integrals methods and numerical Density Matrix Renormalization Group, we revisit the physics of localized magnons and determine the consequences of the DM interaction on the ground state. We have studied the spin current behavior, finding three different regimes. First, a Luttinger-liquid regime where the spin current shows a step behavior as a function of parameter D, at a low magnetic field. Increasing the magnetic field, the system is in the Meissner phase at the m = 1/2 plateau, where the spin current is proportional to the DM parameter. Finally, further increasing the magnetic field and for finite D there is a small stiffness regime where the spin current shows, at fixed magnetization, a jump to large values at D = 0, a phenomenon also due to the flat band.

An effective field theory approach for the $S = 3/2$ bilayer honeycomb antiferromagnet

“…Similar magnon-crystal ground states are present in other frustrated quantum spin system in one-, two-, and three-dimensional systems 43 . Our results are the semiclassical description of the exactly factorized ground state for general spin S, as has been done in some frustrated quantum spin chains 44,45 .…”

Electric field driven flat bands: Enhanced magnetoelectric and electrocaloric effects in frustrated quantum magnets

“…A prototype flat-band model is the sawtooth (or delta) spin chain that has been widely investigated for different realizations such as frustrated quantum spin systems, see, e.g. [23,25,73,75,77,[79][80][81][82][83][84][85][86][87], electronic systems, see, e.g., Refs. [20][21][22][88][89][90][91][92][93][94][95][96] as well as photonic lattices, see, e.g.…”