Cluster-based Haldane state in edge-shared tetrahedral spin-cluster chain: Fedotovite K$_2$Cu$_3$O(SO$_4$)$_3$

TL;DR

This study investigates Fedotovite K$_2$Cu$_3$O(SO$_4$)$_3$, revealing a cluster-based Haldane state in a one-dimensional spin system with edge-shared tetrahedral clusters, supported by experimental and theoretical analyses.

Contribution

The paper demonstrates the emergence of a cluster-based Haldane state in a new quantum spin system with edge-shared tetrahedral clusters, combining experimental and theoretical insights.

Findings

Identification of an effective S=1 Haldane state below 4 K.

Establishment of a link between tetrahedral cluster parity and Haldane state emergence.

Experimental confirmation of triplet ground state in EST clusters.

Abstract

Fedotovite K$_2$Cu$_3$O(SO$_4$)$_3$ is a candidate of new quantum spin systems, in which the edge-shared tetrahedral (EST) spin-clusters consisting of Cu$^{2+}$ are connected by weak inter-cluster couplings to from one-dimensional array. Comprehensive experimental studies by magnetic susceptibility, magnetization, heat capacity, and inelastic neutron scattering measurements reveal the presence of an effective $S$ = 1 Haldane state below $T \cong 4$ K. Rigorous theoretical studies provide an insight into the magnetic state of K$_2$Cu$_3$O(SO$_4$)$_3$: an EST cluster makes a triplet in the ground state and one-dimensional chain of the EST induces a cluster-based Haldane state. We predict that the cluster-based Haldene state emerges whenever the number of tetrahedra in the EST is $even$.