Generation and electrical detection of spin collectivity in monolithic thin-film polymer devices*

Collectivity in paramagnetic spin ensembles, analogous to electric dipoles resonantly driven in the Dicke regime, occurs under magnetic resonance, when the driving field amplitude $B_{\mathrm{1\thinspace }}$reaches the order of the Zeeman field $B_{\mathrm{0}}$. Measurements of spin-dependent transition rates between weakly spin-coupled charge carrier pairs in organic semiconductors have shown that this spin-Dicke regime can be reached experimentally by lowering $B_{\mathrm{0}}$ to a minimum posed by random local hyperfine fields, requiring radio frequency (RF) driving fields, while maximizing $B_{\mathrm{1\thinspace }}$[2,3]. Here we show that this can be accomplished using a microscopic monolithic thin-film device consisting of a polymer diode on a \textasciitilde 1$\mu $m SiO$_{\mathrm{2}}$/SiN layer stack grown on a Cu thin-film wire for strong homogeneous RF excitation, which in turn is supported by a crystalline Si substrate. This setup allows for $B_{\mathrm{1}}$\textgreater 2mT, and thus the observation of spin-collectivity in super-yellow (SY) poly (p-phenylene vinylene) (PPV), a polymer with much stronger local hyperfine fields than the deuterated polymers previously used [2]. [1] R.C.Roundy, M. E. Raikh, \textit{Phys.rev. B} 88, 125206 (2013). [2] D. P. Waters et al. \textit{Nature Phys}. 11, 910 (2015). [3] S. L. Bayliss, et al. \textit{Nature Com}. 6, 8534 (2015).