Quantum Phase Interference in Magnetic Molecular Clusters

TL;DR

This paper demonstrates quantum phase interference effects in magnetic molecular clusters, providing direct evidence of topological quantum phases through tunnel splitting oscillations and ac susceptibility measurements.

Contribution

It presents the first direct measurement of topological quantum interference in magnetic molecules using ac susceptibility, extending understanding of quantum spin phases.

Findings

Oscillations of tunnel splittings as a function of magnetic field observed.

Parity effect in quantum transitions demonstrated.

Quantum interference measurable via ac susceptibility in thermal regime.

Abstract

The Landau Zener model has recently been used to measure very small tunnel splittings in molecular clusters of Fe8, which at low temperature behaves like a nanomagnet with a spin ground state of S = 10. The observed oscillations of the tunnel splittings as a function of the magnetic field applied along the hard anisotropy axis are due to topological quantum interference of two tunnel paths of opposite windings. Transitions between quantum numbers M = -S and (S - n), with n even or odd, revealed a parity effect which is analogous to the suppression of tunnelling predicted for half integer spins. This observation is the first direct evidence of the topological part of the quantum spin phase (Berry or Haldane phase) in a magnetic system. We show here that the quantum interference can also be measured by ac susceptibility measurements in the thermal activated regime.