Spin qubits in hexagonal Boron Nitride

A central goal of future light-based quantum technologies is a global quantum network - a distribution of quantum states and entanglement between any two points on the globe. Such a network is thought to have major implications for secure global communication, QKD, quantum computation and even a quantum internet. A major challenge for quantum networks is finding the right materials that can send and recover quantum information via photons. Recently, we have discovered a quantum coherent S=1 defect in hexagonal Boron Nitride. This system shows room temperature spin coherence, high brightness, high ODMR contrast and a low-symmetry S=1 electronic structure. We are pursuing this system for application in quantum networks and nanoscale quantum sensing.

Publications:

A quantum coherent spin in a two-dimensional material at room temperature. H. L. Stern*, C. M. Gilardoni*, Q. Gu, S. Eizagirre Barker, O. Powell, X. Deng, L. Follet, C. Li, A. Ramsay, H. H. Tan, I. Aharonovich and M. Atature, Nature Materials, accepted (2024).

Room-temperature optically detected magnetic resonance of single defects in hexagonal boron nitride , H.L Stern*, Q. Gu *, J. Jarman*, S. Eizagirre Barker, N. Mendelson, D. Chugh, S. Schott, H. H. Tan, H. Sirringhaus, I. Aharonovich and M. Atature. Nature Communications, 13, 681, (2022).

Spectrally resolved photodynamics of individual emitters in large-area monolayers of hexagonal Boron Nitride, H.L. Stern, R. Wang, R. Mizuta, J.C. Stewart, T. D. Roberts, R. Wai, N. S. Ginsberg, D. Klenerman, S. Hofmann and S. Lee. ACS Nano, 13, 4538-4547, (2019).

*= these authors contributed equally

Molecular spins for solar energy conversion.

Carbon-based molecular semiconductors are materials that can efficiently absorb solar photons to generate free charges. This makes these materials exciting candidates for use in solar cells, as they are solution-processable, affordable and tunable. In addition, a class of these materials offers ways of boosting solar cell efficiencies beyond theoretical limits (Shockley Queisser limit) - via an ultrafast process that converts one photo-generated spin singlet exciton to two spin triplet excitons (single exciton fission). Our past work has shown how singlet exciton fission can proceed, even when the energy of the two spin triplet excitons is greater than the energy of the absorbed photon, ie. endothermic. Using a combination of ultrafast transient absorption and photoluminescence spectroscopies we identified a critical intermediate excited state in solution and the solid state.

Publications:

Elusive excited states identified from cutting edge molecular movies. A. J. Musser and H. L Stern, Nature, News and Views, (2023).

Vibronically coherent ultrafast triplet-pair formation and subsequent thermally activated dissociation control efficient endothermic singlet fission. H. L Stern, A. Cheminal, S. R Yost, K. Broch, S.L. Bayliss, K. Chen, M. Tabachyk, K. Thorley, N. Greenham, J. M Hodgkiss, J. Anthony, M. Head-Gordon, A.J Musser, A. Rao and R. H. Friend. Nature Chemistry, 9, 1205-1212 (2017).

Elucidation of excitation energy dependent correlated triplet pair formation pathways in an endothermic singlet fission system. A. Thampi, H. L. Stern, A. Cheminal, M. J.Y. Tayebjee, A.J. Petty, J.E. Anthony and A. Rao. JACS, 140,13 (2017).

Synthesis and exciton dynamics of donor-orthogonal acceptor conjugated polymers: Reducing the singlet–triplet energy gap. D.M.E. Freeman, A.J. Musser, J.M. Frost, H. L. Stern, A.K. Forster, K. J. Fallon, A.G. Rapidis, F. Cacialli, I. McCulloch, T.M. Clarke, R.H Friend and H. Bronstein. JACS, 139, 11073-11080 (2017),

Limits for Recombination in a Low Energy Loss Organic Heterojunction. S. M. Menke, A. Sadhanala, M. Nikolka, N. A. Ran, M. K. Ravva, S. Abdel-Azeim, H. L. Stern, M. Wang, H. Sirringhaus, T.Q. Nguyen, J.L. Brédas, G. C. Bazan and R. H. Friend. ACS Nano, 10,12 (2016).

Identification of a triplet pair intermediate in singlet exciton fission in solution. H. L. Stern, A.J. Musser, S. Gelinas, P. Parkinson, L. M. Herz, M. J. Bruzek, J. Anthony, R. H. Friend, and B.J. Walker, PNAS, 111, 25 (2015).

Singlet exciton fission in solution. H. L Stern, A.J. Musser and R.H. Friend. Photochemistry, 43. (2015).