At the extremes of spin dynamics: organic co-crystals and nv− diamond as materials for masers and microwave mode cooling

Abstract

The suitability of the three charge transfer co-crystals anthracene with 1,2,4,5-tetracyanobenzene (A:TCNB), phenazine with 1,2,4,5-tetracyanobenzene (PNZ:TCNB) and acridine with 1,2,4,5- tetracyanobenzene (Acri:TCNB) as maser gain media was assessed. The ability for NV− centres in diamond to act as a spin-cold material that can cool a microwave mode at 2872 MHz is also presented. Through the construction of a homemade transient electron paramagnetic resonance (trEPR) spectrometer, the triplet EPR signals of all four materials were measured and used to find their resonant frequencies and solve their triplet spin dynamics. The co-crystals A:TCNB and PNZ:TCNB were shown by simulation to feasibly support masing at transition frequencies above 2 GHz, but experiments with A:TCNB could not yet produce masing signals. NV− diamond on the other hand succeeded as a microwave mode cooler, able to cool the mode from room temperature down to 188 K and hold that temperature for 10 milliseconds when measured using a heterodyne receiver setup.