'Hole-digging' in ensembles of tunneling Molecular Magnets

TL;DR

This paper uses Monte Carlo simulations to analyze the formation and evolution of tunneling holes in ensembles of magnetic molecules, revealing Lorentzian line-shapes and rapid disintegration in polarized samples.

Contribution

It demonstrates that the tunneling hole line-shape is Lorentzian and characterizes the time evolution of the hole width in magnetic molecule ensembles.

Findings

The tunneling hole has a Lorentzian shape in weakly polarized samples.

The initial hole width is approximately equal to the nuclear spin multiplet half-width E_0.

Hole width increases rapidly after the tunneling relaxation time τ_0.

Abstract

The nuclear spin-mediated quantum relaxation of ensembles of tunneling magnetic molecules causes a 'hole' to appear in the distribution of internal fields in the system. The form of this hole, and its time evolution, are studied using Monte Carlo simulations. It is shown that the line-shape of the tunneling hole in a weakly polarised sample must have a Lorentzian lineshape- the short-time half-width $\xi_o$ in all experiments done so far should be $\sim E_0$, the half-width of the nuclear spin multiplet. After a time $\tau_o$, the single molecule tunneling relaxation time, the hole width begins to increase rapidly. In initially polarised samples the disintegration of resonant tunneling surfaces is found to be very fast.