Spectroscopic techniques are an essential tool in probing electronic, optical and structural properties of materials.
Besides those techniques, numerical simulations of spectroscopic properties help in the interpretation of the experimental
results, and may even guide and motivate new experiments. In this context, we develop theoretical and numerical approaches,
as well as computational tools, within the framework of manybody perturbation theory and density functional theory.
Manybody perturbation theory allows to systematically capture correlation effects responsible for emergent collective behaviours
in an electronic system. Combining manybody perturbation theory with densityfunctional theory results in universal,
parameterfree numerical approaches that allows to quantitatively address spectroscopic properties of materials, given the
atomic positions as the only input. Indeed, those techniques are nowadays the stateoftheart to simulate e.g. optical absorption,
electron energy loss and photo emission spectra for a broad range of materials.
Notwithstanding this success, active development of those approaches, and the associated computational tools is still needed. Two of
the major challenges are:
a. The application of the abovementioned approaches to large and complex systems, as those that come into play in problems of
technological interest (e.g. nanostructures, interfaces, defects).
b. The extension of those approaches to address realtime, femtosecond spectroscopic techniques, that provides information on the
photoinduced electron dynamics and changes in the structures and properties of an electronic system.
Following those challenges, our research proceeds along two main lines:
1. Designing of strategies and efficient numerical algorithms to treat systems with a large number of degrees of freedom.
2. Development of theoretical and numerical approaches within nonequilibrium Green's function theory to simulate realtime femtosecond
spectroscopy experiments.
Theoretical and numerical progresses from both lines are implemented in Yambo, a code that
allows the calculation of excitedstate properties of materials. The code results from the collaboration of several researchers and being
publicly available (and interfaced with two of the most used, publicly available densityfunctional codes) it is used by researchers all
over the world.
From: NanoLetters 9 (2009) 2820
Related/Relevant Publications:
ExcitonPlasmon States in Nanoscale Materials: Breakdown of the TammDancoff Approximation
Grüning, M; Marini, A; Gonze, X, Nano Letters 9 (2009) 2820
DOI: 10.1021/nl803717g
Realtime approach to the optical properties of solids and nanostructures: Timedependent BetheSalpeter equation
Attaccalite, C.; Grüning, M.; Marini, A. Physical Review B 84 (2011) 245110
DOI: 10.1103/PhysRevB.84.245110
Yambo: An ab initio tool for excited state calculations
Marini, A; Hogan, C; Grüning, M; Varsano D. Computer Physics Communications, 180 (2009) 1392
DOI: 10.1016/j.cpc.2009.02.003
Quasiparticle calculations of the electronic properties of ZrO2 and HfO2 polymorphs and their interface with Si
Grüning, M; Shaltaf, R; Rignanese, GM Physical Review B 81 (2010) 035330
DOI: 10.1103/PhysRevB.81.035330
Localfield and excitonic effects in the optical response of alphaalumina
Marinopoulos, AG; Gruning, M
Physical Review B 83, (2011) 19529
DOI: 10.1103/PhysRevB.83.195129
Staff involved
