Room-temperature Microscopy Achieves Spatially-Resolved Coherence in Molecular Spin Thin-Films

Molecular spin-based sensing holds immense promise, leveraging the tunability of these systems in diverse forms like crystals and films! Adrian Mena, Nicholas P. Sloane, and Max R. Bonengel, from the School of Physics at UNSW Sydney, alongside Dane R. McCamey et al., have now demonstrated spatially-resolved coherence of organic molecular spins at room temperature , a significant step towards realising practical, high-resolution sensors! Their research combines coherent control with microscopy to map coherence properties in both pentacene-doped p-terphenyl thin-films and micro-crystals, revealing substantial variations in sensitivity within films (approximately 7.6%) but remarkably uniform performance in micro-crystals (just 1.3%)! Crucially, they extend this technique to a nano-crystal, maintaining coherence times of 1.09s and a 25% contrast, suggesting a pathway to highly sensitive and stable nanoscale sensing platforms.

The research team achieved room-temperature optically detected coherent control combined with microscopy to image the coherence properties of both thin-films and micro-crystals of pentacene doped p-terphenyl. This innovative approach allows for detailed characterisation of molecular spin behaviour in different solid-state environments, addressing a key challenge in developing nanoscale quantum sensors. Experiments show that thin-films exhibit significant variability in both contrast and coherence times, resulting in a magnetic field sensitivity variation of approximately 7.6 %.

The study reveals that applying this technique to micro-crystals yields substantially lower sensitivity variability, measuring only 1.3 %, and crucially, no evidence of coherence loss towards the crystal edge. This finding highlights the benefits of crystalline structures in maintaining spin coherence, a critical factor for precise sensing applications. Furthermore, the researchers performed optically-detected coherent control on a nano-crystal, observing minimal loss in coherence and contrast compared to the bulk crystal, achieving a coherence time of 1.09μs and a contrast of 25 %. This demonstrates the potential for miniaturising molecular spin-based sensors without sacrificing performance, opening doors for high-proximity sensing applications.

This work establishes a powerful method for assessing the suitability of different molecular spin deployment strategies for quantum sensing. The experimental setup, utilising a co-planar waveguide and a 520nm laser for excitation, enables parallel readout of sample regions, providing a rapid platform to study coherence properties in both ordered and disordered substrates. The research establishes a clear link between material structure and coherence, guiding future efforts towards developing high-resolution quantum sensors.

The team’s findings are particularly significant as they address the trade-off between the high doping ratios and nanometre precision achievable with thin-films, and the enhanced coherence typically observed in crystalline materials. This breakthrough reveals that while thin-films introduce disorder, careful control and characterisation can mitigate these effects, while micro- and nano-crystals offer superior coherence and stability. The ability to maintain coherence in nano-crystals, with a measured time of 1.09μs, is a crucial step towards integrating molecular spins into nanoscale structures and functionalised probes for applications ranging from biological sensing to materials science. This research opens exciting possibilities for developing quantum sensors with unprecedented spatial resolution and sensitivity.

Optically Detected Coherent Control of Molecular Spins

Scientists engineered a spatially resolved optically detected coherent control system0.76 : 0.16 : 0.6 % in thin-films, contrasting with a significantly lower variability of 1.3 % observed in micro-crystals! Further investigation of a nano-crystal revealed minimal loss in coherence and contrast compared to the bulk crystal, achieving a coherence time of 1.09μs and a contrast of 25 %! This innovative approach enables high-proximity quantum sensing and guides efforts towards deploying molecular spins in advanced sensing applications.

Pentacene Spin Coherence in Thin-Films and Micro-Crystals

Scientists achieved room-temperature optically detected coherent control of molecular spins in both thin-films and micro-crystals of pentacene doped p-terphenyl, revealing crucial insights into coherence properties! Experiments revealed that thin-films exhibit significant variation in both contrast and coherence times, leading to an approximate 7.6 % variability in magnetic field sensitivity! The team measured a contrast of 0.55 % with a standard deviation of 0.05 % across the 100nm thick film, doped at 1 %, demonstrating a 9.8 % variation in contrast measurements! Data shows the average coherence time, T2, across the thin-film was 890ns, with a standard deviation of 70ns, resulting in a 7.3 %! Scientists recorded no evidence of coherence loss towards the edge of the micro-crystals, a surprising finding that challenges conventional understanding of solid-state systems! Measurements confirm that the spin polarisation arises from anisotropic intersystem crossing rates, with probabilities of Px : Py : Pz = 0.76 : 0.16 : 0.17μs with a remarkably low variation of only 1 %! Tests prove an unexpected trend where the edge of the crystal exhibits a longer coherence time than the centre, confirmed by averaging measured coherence times with varying radial distances! Specifically, the averaged T2 plotted against radial distance showed a clear increase in coherence time towards the crystal’s edge! Measurements of contrast within the micro-crystal yielded an average of 0.96 % with a variation of 0.5 %, further highlighting the improved coherence compared to the thin-film.

Furthermore, optically-detected coherent control was performed on a nano-crystal, demonstrating minimal loss in coherence and contrast compared to the bulk crystal, with a coherence time of 1.09μs and a contrast of 25 %! These findings suggest that nano-crystals offer a promising platform for high-resolution proximity sensing applications, potentially enabling the detection of smaller fields and improved spatial resolution! The research establishes a foundation for advanced quantum imaging techniques utilising molecular spin systems with enhanced control and sensitivity!

Thin-film versus micro-crystal spin coherence differs significantly in

Scientists have demonstrated room-temperature optically detected coherent control of molecular spins within both thin-films and micro-crystals of pentacene-doped p-terphenyl! This research combines advanced microscopy techniques with coherent control to map the coherence properties of these materials, revealing significant differences in performance based on their physical form. The study establishes that thin-films exhibit substantial variability in both contrast and coherence times, resulting in approximately 7.6% variation in magnetic field sensitivity! In contrast, micro-crystals displayed markedly lower sensitivity variability, only 1.3%, and maintained coherence even at their edges, suggesting superior uniformity.

Furthermore, investigations into nano-crystals showed minimal loss of coherence and contrast compared to bulk crystals, achieving a coherence time of 1.09μs and a contrast of 25%! Quantitative analysis revealed that reducing crystal size led to a sensitivity impairment factor of 1.2 for AC sensing and 1.76 for DC sensing, indicating a manageable trade-off between size and performance. The authors acknowledge that the observed variability in thin-films is attributable to disorder within the material, a limitation that must be addressed for accurate imaging applications. Future research should focus on developing methods for producing and positioning smaller doped molecular crystals, potentially enabling higher resolution precision imaging and opening avenues for optically trapped sensors in spin-based optomechanical experiments.