Quantum-Probe Microscopy Research

Molecular magnetism

Magnetic carbon-based nanomaterials and nanostructures have recently emerged as promising candidates for applications in spintronics. Compared to transition metals, carbon systems display weak spin-orbit and hyperfine couplings, that result in appealing properties such as long spin coherence times and long-range spin interactions. While ideal graphene is not magnetic, an intrinsic spin polarization can develop in some graphene-based nanostructures with well-defined shapes. Thanks to the advent of on-surface synthesis (OSS), performed on suitable metal surfaces in ultra-high vacuum conditions, it is now possible to fabricate custom-crafted nanographenes with full control over their geometry and atomic structure. In our group we design and grow atomically precise graphene nanostructures on metallic substrates and investigate their structural, electronic and magnetic properties by means of STM/STS and AFM. We focus on the emergence of spin states and spin interactions in these purely organic systems and explore methods for tuning them, with the final aim of testing their potential as basic elements in all-carbon spin devices.

Magnetism and superconductivity in low dimensions

Superconducting materials are nowadays in the spotlight for the accelerating development of quantum information technology. Many metals, like Pb, Nb or V, show superconductivity, a phenomenon driven by electron-electron interactions and observable at low temperatures.  In our lab we can study superconducting materials at the atomic scale with a Scanning Tunneling Microscope operating at 1.3K with external magnetic fields up to 3T. When a superconductor is brough in contact with a normal metal like Au, Ag or graphene superconductivity is transferred by the proximity effect. Our main interest is the engineering of novel proximitized superconductors that can host on-surface synthesis of organic molecules and study the interplay of localized spins and superconductivity. In fact, the interaction of atomic and molecular spins with a proximitized superconductor can induce exotic phenomena that are interesting for creating electrically addressable quantum devices.

Nanoscale optoelectronics

In scanning tunneling microscopy-induced luminescence (STM-L), tunneling electrons from the tip of an STM can excite the light emission of single molecules within the STM junction, allowing their optical properties to be investigated with extreme spatial and energetic resolution. To prevent the quenching of the luminescence by the underling metal, the emitters need to be electronically decoupled from the substrate, which can be achieved by, e. g., placing them on ultrathin insulating layers such as few-layer NaCl. The photons emitted from the STM junction are detected outside the vacuum system by a dedicated optical set-up including a spectrometer and cooled charge-coupled device (CCD) camera. 

In particular, we want to investigate, e. g., how the optical properties of single molecules can be modified by external stimuli, or how the covalent coupling of emitters affects their photon emission statistics. The results of our research will have important ramifications for the potential use of single molecules as ultra-sensitive optical sensors or as single-photon sources in quantum information technology.