Block-spiral magnetism: An exotic type of frustrated order

TL;DR

This paper predicts and characterizes a novel magnetic phase called block-spiral order in low-dimensional multi-orbital Hubbard models, expanding understanding of frustrated magnetism without traditional frustration mechanisms.

Contribution

The study introduces the block-spiral state as a new magnetic order in multi-orbital Hubbard models, supported by theoretical modeling and experimental signatures.

Findings

Confirmation of block-magnetism in iron-based ladder materials

Prediction of a new block-spiral magnetic phase

Identification of parity-breaking quasiparticles

Abstract

Competing interactions in Quantum Materials induce novel states of matter such as frustrated magnets, an extensive field of research both from the theoretical and experimental perspectives. Here, we show that competing energy scales present in the low-dimensional orbital-selective Mott phase (OSMP) induce an exotic magnetic order, never reported before. Earlier neutron scattering experiments on iron-based 123 ladder materials, where OSMP is relevant, already confirmed our previous theoretical prediction of block-magnetism (magnetic order of the form $\uparrow\uparrow\downarrow\downarrow$). Now we argue that another novel phase can be stabilized in multi-orbital Hubbard models, the {\it block-spiral state}. In this state, the magnetic islands form a spiral propagating through the chain but with the blocks maintaining their identity, namely rigidly rotating. This new spiral state is stabilized without any apparent frustration, the common avenue to generate spiral arrangements in multiferroics. By examining the behaviour of the electronic degrees of freedom, parity breaking quasiparticles are revealed. Finally, a simple phenomenological model that accurately captures the macroscopic spin spiral arrangement is also introduced, and fingerprints for the neutron scattering experimental detection of our new state are provided.