Faculty and Research

Physics

Biography

Dr. Stolbov received his Ph.D. in Physics from Rostov State University, Russia, in 1982. He worked as a Senior Researcher at Institute of Physics in Rostov State University, Russia, 1983 – 1998. He spent one year as a Research Associate in Texas Center for Superconductivity at the University of Houston before joining Carnegie Institution of Washington as a Postdoctoral Fellow in 1999. He joined Kansas State University as a Research Associate in 2000 and a Research Assistant Professor in 2004. He joined UCF in 2006 where he is an Associate Professor.

Research Areas

During my entire career my research activity was focused on revealing microscopic phenomena responsible for technologically important properties of materials using quantum-mechanical computational techniques and utilizing this knowledge for rational design of advanced materials. The materials in question have been crystals, nanoparticles, metal and oxide surfaces, as well as two-dimensional systems. The phenomena of interest were superconductivity, adsorption and diffusion of atoms and molecules on solid surfaces, and heterogeneous and electro-catalysis. Currently my research is focused on local defects in wide-bandgap semiconductors. Some of such defects may serve as single-photon emitters (SPE) or spin qubits. The SPEs and spin qubits are the building blocks for quantum communication and quantum computing technologies.

To possess the SPE functionality, the defect must have a very specific electronic structure (local electronic states in the band gap) and specific optical excitations. The spin qubits, especially the most valuable ones, with so-called optically controlled initialization, must have specific spin states (triplet and singlet, or quartet and doublet), as well as a specific combination of the optical excitation energies and symmetry accessible for so-called phonon-induced intersystem crossing. Thus, understanding the factors controlling the properties in question and rational design/prediction new defects with the desired properties requires a deep knowledge of various quantum phenomena and the application of advanced computational methods.

In our research, we apply existing knowledge and educated guess to select the defect with potential spin-qubit or SPE properties. Next, we perform the density functional theory (DFT)-based calculation of the ground states of the defect: its possible spin states, formation energy and dynamical stability (from phonon spectra). If these properties are acceptable, we turn to the excited states of the defect calculating the electronic structure within the linear response GW method and optical excitation spectra by solving the Bethe-Salpeter equation (BSE). Using the GW and BSE calculation results we build so-called optical spin-polarization cycle diagram to conclude whether the defect is promising in terms of the SPE or spin-qubit functionalities. Using this approach, we have studied a number of local defects in three-dimensional semiconductors, such as wurtzite AlN, wurtzite and cubic BN, and BeS, as well as two-dimensional hexagonal BN and BeS. As a result, we proposed several defects with promising qubit and SPE properties. We have also revealed the relations among the defect composition and symmetry, its spin state and electronic structure. This knowledge helps us to efficiently predict new promising systems for quantum technologies.

 

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