Exact eigenstates of highly frustrated spin lattices probed in high fields

TL;DR

This paper explores exact eigenstates in highly frustrated spin lattices under high magnetic fields, revealing giant magnetization jumps, extensive degeneracy, and connections to flat band ferromagnetism, with implications for quantum effects and magnetocaloric phenomena.

Contribution

It constructs exact many-body eigenstates for frustrated spin systems, highlighting their role in high-field ground states and exotic magnetic behaviors.

Findings

Presence of giant magnetization jumps in high fields.

Massive degeneracy and extensive zero-temperature entropy.

Connection to flat band ferromagnetism and large magnetocaloric effects.

Abstract

Strongly frustrated antiferromagnets such as the magnetic molecule {Mo72Fe30}, the kagome, or the pyrochlore lattice exhibit a variety of fascinating properties like low-lying singlets, magnetization plateaus as well as magnetization jumps. During recent years exact many-body eigenstates could be constructed for several of these spin systems. These states become ground states in high magnetic fields, and they also lead to exotic behavior. A key concept to an understanding of these properties is provided by independent localized magnons. The energy eigenvalue of these n-magnon states scales linearly with the number n of independent magnons and thus with the total magnetic quantum number M=Ns-n. In an applied field this results in a giant magnetization jump which constitutes a new macroscopic quantum effect. It will be demonstrated that this behavior is accompanied by a massive degeneracy, an extensive (T=0)-entropy, and thus a large magnetocaloric effect at the saturation field. The connection to flat band ferromagnetism will be outlined.