原子核理論研究室

(1)

Title: Ultrafast dynamics in light-harvesting and photovoltaics: a theoretical and experimental investigation

Speaker: Carlo Andrea Rozzi (CNR – Istituto Nanoscienze)

Place: Workshop room, Center for Computational Sciences

Time: May 18, 11:00-12:00

Abstract:

It is known that the primary steps of photoinduced energy and charge transfer occur on extremely fast time scales in many natural and man-made compounds that perform conversion of sunlight into chemical or electrical energy. These processes have traditionally been interpreted in terms of the incoherent kinetics of optical excitations and of charge hopping, but recently signatures of quantum coherence were observed in energy transfer in photosynthetic bacteria and algae [1,2]. We have studied the early steps of photoinduced charge separation in reference systems for artificial photosynthesis and photovoltaics by combining Time-dependent Density Functional Theory simulations of the quantum dynamics and high time resolution femtosecond spectroscopy. Our results show that the coherent coupling between electronic and nuclear degrees of freedom is of key importance for charge delocalization and transfer in both of covalently and non-covalently bonded systems [3,4]. We have exploited the results of our research to design, synthesize and characterize a novel molecular scaffold for photovoltaic applications [5].

[1] Engel, G. S. et al. Nature 446, 782-786 (2007).

[2] Collini, E. et al. Nature 463, 644-647 (2010).

[3] Rozzi, C. A., Falke S. et al., Nat. Comm. 4, 1602 (2013)

[4] Falke S., Rozzi, C. A. et al., Science, 344, 1001 (2014)

[5] Pittalis S., et al., Adv. Func. Mat. (2014)

(2)

Title: A roundtrip journey from spin-entanglement in atoms and molecules

to density functional theory

Speaker: Stefano Pittalis (CNR – Istituto Nanoscienze)

Place: Workshop room, Center for Computational Sciences

Time: 13:30-14:30

Abstract:

I will present an investigation on spin entanglement in many-electron systems within the framework of density functional theory [1]. In particular, I will show that, the entanglement length — which is extracted from the spatial dependence of the local concurrence — is a sensitive indicator of atomic shells, and reveals the character, covalent or metallic, of chemical bonds. These findings shed light on the remarkable success of modern density functionals, which tacitly employ the entanglement length as a variable, and open the way to further research on entanglement-based functionals.

[1] S. Pittalis, F. Troiani, C. A. Rozzi, G. Vignale, Phys. Rev. B 91, 075109 (2015)