The V15 molecule, a multi-spin two-level system: adiabatic LZS transition with or without dissipation and Kramers theorem

TL;DR

This paper investigates the V15 molecule's multi-spin system, demonstrating how its complex spin structure leads to a gapped half-integer spin state, and explores adiabatic Landau-Zener-Stuckelberg transitions under various conditions.

Contribution

It reveals the multi-spin origin of the gapped half-integer spin in V15 and analyzes adiabatic LZS transitions with and without dissipation using experimental data.

Findings

V15's half-integer spin is gapped due to multi-spin effects.

Magnetization experiments support adiabatic LZS spin reversal.

Kramers degeneracy is preserved despite the gap.

Abstract

The so-called V15 molecule is formed of 15 spins 1/2 antiferromagnetically coupled. The resultant spin is equal to 1/2. Contrary to what is expected at first sight, this half-integer spin is gapped. We show that this is a consequence of the multi-spin character of the molecule. Time reversal symmetry (Kramers theorem) is preserved due to the existence of a groundstate degeneracy larger than 2. Magnetization experiments have been performed at different temperatures, sweeping-field rates and couplings with the cryostat. Their interpretation in terms of the Landau-Zener-Stuckelberg model gives evidence for adiabatic LZS spin reversal with and without dissipation.