Spin frustration and fermionic entanglement in an exactly solved hybrid diamond chain with the localized Ising spins and mobile electrons

TL;DR

This paper provides an exact solution for a hybrid spin-electron diamond chain, revealing how fermionic entanglement and spin frustration are interconnected yet distinct phenomena, with implications for quantum states in magnetic systems.

Contribution

It introduces an exact analytical approach to study spin frustration and fermionic entanglement in a hybrid diamond chain with localized Ising spins and mobile electrons.

Findings

Fermionic entanglement appears only in a frustrated paramagnetic phase.

Thermal fluctuations can induce quantum entanglement above non-frustrated states.

Spin frustration and fermionic entanglement are related but independent phenomena.

Abstract

The strongly correlated spin-electron system on a diamond chain containing localized Ising spins on its nodal lattice sites and mobile electrons on its interstitial sites is exactly solved in a magnetic field using the transfer-matrix method. We have investigated in detail all available ground states, the magnetization processes, the spin-spin correlation functions around an elementary plaquette, fermionic quantum concurrence and spin frustration. It is shown that the fermionic entanglement between mobile electrons hopping on interstitial sites and the kinetically-induced spin frustration are closely related yet independent phenomena. In the ground state, quantum entanglement only appears within a frustrated unsaturated paramagnetic phase, while thermal fluctuations can promote some degree of quantum entanglement above the non-frustrated ground states with saturated paramagnetic or classical ferrimagnetic spin arrangements.