Dense pentacene cocrystal demonstrates room-temperature coherent control

Authors:Noella D'Souza, Guangzhao Chen, Madhur Parashar, Wern Ng, Brandon Wallace, Tatiana Lindahl, Tanner S. Volek, Lam Lam, Joseph Garrett, Emanuel Druga, Sean T. Roberts, Jeffrey Reimer, Harpreet Singh, Liang Z. Tan, Riccardo Montis, Ashok Ajoy

Abstract:Maximizing the number of addressable spins within a fixed volume can improve ensemble quantum sensor sensitivity, but dense packing usually increases dipolar interactions and excited-state transport, shortening coherence and suppressing optical readout. Here we report a 2:1 cocrystal of 6,13-dihydropentacene and pentacene (DHP/Pc) containing 33.3 mol% pentacene ($3.3\times10^{5}$ ppm; $9.51\times10^{20}$ cm$^{-3}$), a volumetric spin-site density more than two orders of magnitude above previous benchmarks, NV-diamond and pentacene-doped p-terphenyl (PDP). Despite this density, DHP/Pc exhibits microsecond spin coherence, room-temperature optically detected magnetic resonance and coherent control. Time-resolved measurements indicate that the long-lived triplet population is generated predominantly by intersystem crossing and exhibits strong, non-thermal sublevel polarization. Density-functional theory calculations further suggest that the native cocrystal geometry weakens electronic coupling between neighboring pentacenes, while the higher DHP triplet energy creates a barrier to triplet migration. These results identify molecular packing and coformer triplet energetics as complementary design parameters for preserving coherence in high spin-site density systems, demonstrating cocrystallization as a promising route to dense, optically addressable spin materials for room-temperature ensemble quantum sensing.

arXiv:2609.28912 [quant-ph]

(or arXiv:2609.28912v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2609.28912 arXiv-issued DOI via DataCite (pending registration)