ECAMP 15

Organic dye molecules doped in organic host crystal provide an exquisite platform for quantum optics because they can reach Fourier-limited spectra at low temperatures. This is in large part due to the highly ordered and stable crystal structures, which provide a low-noise environment, thus minimizing spectral diffusion and dephasing. Many important fundamental studies and technological applications, however, require quantum emitters to be exposed on surfaces. To date, Fourier-limited spectra have remained elusive for quantum emitters on surfaces. In fact, the general wisdom expects surfaces to be intrinsically unsuitable for such studies because they contain defects and contaminants.

In our recent work, we show that it is possible to achieve Fourier-limited electronic transitions for molecules on pristine surfaces of an organic crystal. We have developed a novel sample preparation method, where molecules are sublimated onto the pristine surface of an organic crystal at cryogenic temperatures. We provide detailed quantitative studies on the resulting inhomogeneous broadening at the ensemble level and the behavior of the homogeneous linewidth at the single-molecule level. By comparing the spectral properties of the same molecular species in the gas phase with its properties on the surface and bulk, we shed light on several fundamental aspects of guest-host interactions. This study constitutes an important step in combining high-resolution spectroscopy and quantum optical studies with techniques such as AFM and STM, which provide direct access to individual molecules.