近日，英国剑桥大学Friend, Richard H.团队揭示了有机双自由基中的明亮三重态和明亮电荷分离单重态激子实现自旋态的光学读写。2025年7月29日，《自然-化学》杂志发表了这一成果。

电子自旋态的光学控制对于量子传感和计算应用非常重要，正如金刚石氮空位中心所发展的那样。这需要电子激发，激子，带净自旋。

研究组报告了一种分子双自由基，其中两个三烷基自由基通过一个间位连接的芴桥连接。单重态激子的能量比三重态激子低，因为电子从一个自由基非成键轨道转移到另一个是非成键轨道是允许自旋的，这是由非成键能级的双重占据的充电能量决定的。两个激子在640和700 nm，效率接近单位。

基态交换能低至60μeV，允许控制基态自旋居数。研究组展示了自旋选择性系统间交叉和相干微波控制。他们报道了高达8%的光致发光对比在微波共振。单线态Mott-Hubbard激子与“带隙”激子的调谐为自旋光学材料提供了一个新的设计平台。

附：英文原文

Title: Bright triplet and bright charge-separated singlet excitons in organic diradicals enable optical read-out and writing of spin states

Author: Chowdhury, Rituparno, Murto, Petri, Panjwani, Naitik A., Sun, Yan, Ghosh, Pratyush, Boeije, Yorrick, Cordeiro, Chiara Delpiano, Derkach, Vadim, Woo, Seung-Je, Millington, Oliver, Congrave, Daniel G., Fu, Yao, Mustafa, Tarig B. E., Monteverde, Miguel, Cerd, Jess, Londi, Giacomo, Behrends, Jan, Rao, Akshay, Beljonne, David, Chepelianskii, Alexei, Bronstein, Hugo, Friend, Richard H.

Issue&Volume: 2025-07-29

Abstract: Optical control of electron spin states is important for quantum sensing and computing applications, as developed with the diamond nitrogen vacancy centre. This requires electronic excitations, excitons, with net spin. Here we report a molecular diradical where two trityl radical groups are coupled via a meta-linked fluorene bridge. The singlet exciton is at lower energy than the triplet because electron transfer from one of the radical non-bonding orbitals to the other is spin allowed, set by the charging energy for the double occupancy of the non-bonding level, the Hubbard U. Both excitons give efficient photoluminescence at 640 and 700nm with near unity efficiency. The ground state exchange energy is low, 60μeV, allowing control of ground state spin populations. We demonstrate spin-selective intersystem crossing and show coherent microwave control. We report up to 8% photoluminescence contrast at microwave resonance. This tuning of the singlet Mott–Hubbard exciton against the ‘bandgap’ exciton provides a new design platform for spin–optical materials.

DOI: 10.1038/s41557-025-01875-z

Source: https://www.nature.com/articles/s41557-025-01875-z