Burak Gürlek M.Sc.

Stimulated Raman transition in a single molecule

Johannes Zirkelbach, Burak Gürlek, Masoud Mirzaei, Alexey Shkarin, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar

The small cross section of Raman scattering has hampered the direct study of this eect at the<br>single molecule level. By exploiting the high Franck-Condon factor of a common-mode resonance,<br>choosing a large vibrational frequency dierence in electronic ground and excited states, and operation<br>at T < 2K, we succeed at driving a coherent stimulated Raman transition in a single molecule.<br>We observe and model a spectral splitting that serves as a characteristic signature of the coherent<br>phenomenon at hand. Our study sets the ground for exploiting the intrinsically ecient coupling<br>of the vibrational and electronic degrees of freedom in molecules for quantum optical operations in<br>the solid state.

High-resolution vibronic spectroscopy of a single molecule embedded in a crystal

Johannes Zirkelbach, Masoud Mirzaei, Irena Deperasińska, Boleslaw Kozankiewicz, Burak Gürlek, Alexey Shkarin, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar

Vibrational levels of the electronic ground states in dye molecules have not been previously explored at high resolution<br>in solid matrices. We present new spectroscopic measurements on single polycyclic aromatic molecules of dibenzoter-<br>rylene embedded in an organic crystal made of para-dichlorobenzene. To do this, we use narrow-band continuous-wave<br>lasers and combine spectroscopy methods based on fluorescence excitation and stimulated emission depletion (STED)<br>to select individual vibronic transitions at a resolution of ∼30 MHz dictated by the linewidth of the electronic ex-<br>cited state. In this fashion, we identify several exceptionally narrow vibronic levels in the electronic ground state with<br>linewidths down to values around 2 GHz. Additionally, we sample the distribution of vibronic wavenumbers, relax-<br>ation rates, and Franck-Condon factors, both in the electronic ground and excited states for a handful of individual<br>molecules. We discuss various noteworthy experimental findings and compare them with the outcome of DFT cal-<br>culations. The highly detailed vibronic spectra obtained in our work pave the way for studying the nanoscopic local<br>environment of single molecules. The approach also provides an improved understanding of the vibrational relaxation<br>mechanisms in the electronic ground state, which may help to create long-lived vibrational states for applications in<br>quantum technology.

Engineering long-lived vibrational states for an organic molecule

Burak Gürlek, Vahid Sandoghdar, Diego-Martin Cano

The optomechanical character of molecules was discovered by Raman about one century ago. Today, molecules are promising contenders for high-performance quantum optomechanical platforms because their small size and large energy-level separations make them intrinsically robust against thermal agitations. Moreover, the precision and throughput of chemical synthesis can ensure a viable route to quantum technological applications. The challenge, however, is that the coupling of molecular vibrations to environmental phonons limits their coherence to picosecond time scales. Here, we improve the optomechanical quality of a molecule by several orders of magnitude through phononic engineering of its surrounding. By dressing a molecule with long-lived high-frequency phonon modes of its nanoscopic environment, we achieve storage and retrieval of photons at millisecond time scales and allow for the emergence of single-photon strong coupling in optomechanics. Our strategy can be extended to the realization of molecular optomechanical networks.

Quantum metamaterials with magnetic response at optical frequencies

Rasoul Alaee Khanghah, Burak Gürlek, Mohammad Albooyeh, Diego-Martin Cano, Vahid Sandoghdar

We propose novel quantum antennas and metamaterials with strong magnetic response at optical frequencies. Our design is based on the arrangement of natural atoms with only electric dipole transition moments at distances smaller than a wavelength of light but much larger than their physical size. In particular, we show that an atomic dimer can serve as a magnetic antenna at its antisymmetric mode to enhance the decay rate of a magnetic transition in its vicinity by several orders of magnitude. Furthermore, we study metasurfaces composed of atomic bilayers with and without cavities and show that they can fully reflect the electric and magnetic fields of light, thus, forming nearly perfect electric/magnetic mirrors. The proposed quantum metamaterials can be fabricated with available state-of-the-art technologies and promise several applications both in classical optics and quantum engineering.

suggested by editors

Molecule-photon interactions in phononic environments

Michael Reitz, Christian Sommer, Burak Gürlek, Vahid Sandoghdar, Diego-Martin Cano, Claudiu Genes

Molecules constitute compact hybrid quantum optical systems that can interface photons, electronic degrees of freedom, localized mechanical vibrations, and phonons. In particular, the strong vibronic interaction between electrons and nuclear motion in a molecule resembles the optomechanical radiation pressure Hamiltonian. While molecular vibrations are often in the ground state even at elevated temperatures, one still needs to get a handle on decoherence channels associated with phonons before an efficient quantum optical network based on optovibrational interactions in solid-state molecular systems could be realized. As a step towards a better understanding of decoherence in phononic environments, we take here an open quantum system approach to the nonequilibrium dynamics of guest molecules embedded in a crystal, identifying regimes of Markovian versus non-Markovian vibrational relaxation. A stochastic treatment, based on quantum Langevin equations, predicts collective vibron-vibron dynamics that resembles processes of sub- and super-radiance for radiative transitions. This in turn leads to the possibility of decoupling intramolecular vibrations from the phononic bath, allowing for enhanced coherence times of collective vibrations. For molecular polaritonics in strongly confined geometries, we also show that the imprint of optovibrational couplings onto the emerging output field results in effective polariton cross-talk rates for finite bath occupancies.

Manipulation of Quenching in Nanoantenna–Emitter Systems Enabled by External Detuned Cavities: A Path to Enhance Strong-Coupling

Burak Gürlek, Vahid Sandoghdar, Diego-Martin Cano

We show that a broadband Fabry Perot microcavity can assist an emitter coupled to an off-resonant plasmonic nanoantenna to inhibit the nonradiative channels that affect the quenching of fluorescence. We identify the interference mechanism that creates the necessary enhanced couplings and bandwidth narrowing of the hybrid resonance and show that it can assist entering into the strong coupling regime. Our results provide new possibilities for improving the efficiency of solid-state emitters and accessing diverse realms of photophysics with hybrid structures that can be fabricated using existing technologies.