arXiv subjects

Zachary Rex

Publications and source records attributed to Zachary Rex.

3 recordsLinked to original sources

arXiv2026

Quantitative Theory for the Amplitude of Fluorescence Quantum Beats from Geminate Triplet-Pair Fusion

We derive the amplitude of quantum-beats in the fluorescence from geminate triplet-exciton fusion in rubrene and tetracene from the full set of parameters that characterize triplet exciton dynamics. We find that the amplitude depends on the fission time in tetracene, but does not do so in rubrene, where it is determined by the dimensionality of triplet transport. Kinetic Monte Carlo simulations reproduce the experimental data in both materials, for a fission time of the order of 200 ps and isotropic triplet transport int tetracene, and for a triplet hopping time along the herringbone axis of 250 ps and anisotropic transport in rubrene.

cond-mat.other↗

arXiv2025

Transport-Induced Decoherence of the Entangled Triplet Exciton Pair

Decoherence effects for entangled triplet pairs in organic molecular crystals are analyzed for the case when excitons can hop between inequivalent lattice sites. The fluorescence quantum beats caused by quantum interference upon triplet-triplet recombination into an emissive singlet state are predicted as a function of hopping time and magnetic field based on a Monte Carlo analysis. Depending on exciton hopping rates, it is possible to have complete global decoherence and suppression of fluorescence quantum beats in the limit of zero magnetic field, and to have quantum beats that decay at different rates depending on magnetic field strength.

quant-ph↗

arXiv2024

The persistence of spin coherence in a crystalline environment

We analyze quantum interference in the triplet-exciton pair generated by singlet exciton fission in a molecular crystal, and introduce transport-induced dephasing (TID) as a key effect that can suppress the expected fluorescence quantum beats when the triplet-exciton wavefunction can localize on inequivalent sites. TID depends on the triplet-exciton hopping rate between inequivalent sites and on the energy-shifts among the stationary states of the entangled triplet pair in different spatial configurations. The theoretical model is confirmed by experiments in rubrene single crystals, where triplet pairs remain entangled for more than 50 ns but quantum beats are suppressed by TID within a few nanoseconds when the magnetic field is misaligned by just a few degrees from specific symmetric directions. Our experiments deliver the zero-field parameters for the rubrene molecule in its orthorhombic lattice and information on triplet-exciton transport, in particular the triplet-exciton hopping rate between inequivalent sites, which we evaluate to be of the order of 150 ps in rubrene.

cond-mat.mes-hall↗