29/11/2018/ at 14:00h
IF - predavaonica u zgradi Mladen Paić
Understanding fundamental processes that bring about the characteristic time scales of single-particle and collective excitations in 2D materials and metallic surfaces is a long-standing goal in solid state physics. Various experimental spectroscopy techniques in time domain, e.g., time-resolved electron, optical and vibrational spectroscopies, turned out to play a key role in comprehending the aforesaid mechanisms. In these measurements the non-equilibrium condition is achieved between excited electron and phonon degrees of freedom, which allows us to disentangle them. Along this investigational path, ample attention is given to graphene and similar atomically thin layers, where quite valuable and interesting measurements of carrier and optical phonon lifetimes were carried out by means of trARPES and ultrafast Raman spectroscopy, respectively. Especially interesting time-resolved measurements were also done on metallic surfaces, where the aforementioned techniques are utilized to understand the microscopic processes underlying surface reactions, e.g., photo-induced dissociation of diatomic molecules on surfaces. The ingredient that brings together these examples is the non-adiabatic electron-phonon coupling, which is believed to be a vital mechanism behind relaxation of excited (electron and vibrational) states in 2D materials and metallic surfaces. Yet our quantitative understanding is still in its infancy despite of tremendous interest and experimental efforts, which is mainly due to a lack of corresponding theoretical methods based in first principles.
In this presentation I will deliver the work done on my doctoral and postdoctoral studies that is intimately related to the ultrafast dynamics of 2D materials and metallic surfaces. Regarding the theoretical frameworks that I developed, I will present quantitative methods for simulating dissipation of plasmons due to electron-phonon coupling, non-equilibrium vibrational relaxation, as well as transient optical and electronic excitations. In addition, I will show the corresponding results for plasmon decay in highly-doped graphene, transient optical absorption in pristine graphene, transient phonon relaxation in CO/Cu(100) and in magnesium diboride, to name a few. Finally, the presentation will also contain my future plans and investigation course that fit to current and future projects at Institute of Physics.