Time-dependent exchange creates the time-frustrated state of matter

TL;DR

This paper introduces a novel state called time frustrated matter (TFM) in nanomagnet arrays, where retarded exchange interactions cause non-Markovian dynamics and temporal frustration, expanding the understanding of frustrated magnetic systems.

Contribution

It demonstrates the emergence of a new time-dependent frustrated state of matter driven by retarded exchange interactions in nanomagnet systems, a paradigm shift from spatial to temporal frustration.

Findings

Development of time-core frustration in nanomagnet arrays

Observation of non-Markovian, time-dependent exchange interactions

Identification of a new state called time frustrated matter (TFM)

Abstract

Magnetic systems governed by exchange interactions between magnetic moments harbor frustration that leads to ground state degeneracy and results in the new topological state often referred to as a frustrated state of matter (FSM). The frustration in the commonly discussed magnetic systems has a spatial origin. Here we demonstrate that an array of nanomagnets coupled by the real retarded exchange interactions develops a new state of matter, time frustrated matter (TFM). In a spin system with the time-dependent retarded exchange interaction, a single spin-flip influences other spins not instantly but after some delay. This implies that the sign of the exchange interaction changes, leading to either ferro- or antiferromagnetic interaction, depends on time. As a result, the system's temporal evolution is essentially non-Markovian. The emerging competition between different magnetic orders leads to a new kind of time-core frustration. To establish this paradigmatic shift, we focus on the exemplary system, a granular multiferroic, where the exchange transferring medium has a pronounced frequency dispersion and hence develops the TFM.