Non-chiral spin frustration versus highly degenerate ferromagnetic state with local chiral degrees of freedom of an exactly solvable spin-electron planar model of inter-connected trigonal bipyramids

TL;DR

This paper analyzes an exactly solvable spin-electron model with bipyramidal plaquettes, revealing complex frustration phenomena, local chiral degrees of freedom, and reentrant frustration behavior near phase transitions.

Contribution

It introduces a detailed analysis of frustration in a solvable spin-electron model, highlighting the coexistence of unfrustrated ferromagnetic and frustrated disordered phases with local chiral degrees of freedom.

Findings

Ground state includes unfrustrated ferromagnetic phase with chiral electron degrees of freedom

Frustration persists in the electron sub-lattice at finite temperatures within the disordered phase

Reentrant frustration behavior occurs with three consecutive frustration temperatures

Abstract

The frustration phenomenon in an exactly solvable spin-electron planar model constituted by identical bipyramidal plaquettes is discussed within the Toulouse's and dos Santos and Lyra's frustration concepts. It is shown that the ground state of the model contains the unfrustrated spontaneously ordered quantum ferromagnetic phase with local chiral degrees of freedom in the electron sub-lattice and the disordered quantum one, where both the Ising and electron sub-lattices are frustrated. The frustration of the latter sub-lattice persists at finite temperatures, but only in the disordered region. It finally vanishes at a certain frustration temperature. The reentrant behaviour of the frustration in the electron sub-lattice with three consecutive frustration temperatures due to a competition with the unfrustrated ferromagnetic spin arrangement near the ground-state phase transition can also be observed.