Berlin 2018 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 34: Focus Session: Frontiers of Electronic-Structure Theory: Correlated Electron Materials VII (joint session O/TT/MM/DS/CPP)

DS 34.6: Vortrag

Donnerstag, 15. März 2018, 16:30–16:45, HL 001

Reduced Density Matrix Theory for Coupled Fermion-Boson Systems — •Florian Buchholz¹, Iris Theophilou¹, Michael Ruggenthaler¹, Heiko Appel¹, and Angel Rubio^1,2,3 — ¹MPSD, Hamburg, Germany — ²CCQ, The Flatiron Institute, New York, United Sates — ³Nano-bio Spectroscopy Group, San Sebastián, Spain

Reduced density matrix (RDM) theory proved to be successful in describing a wide range of many-body problems that are not easily accessible by the more common many-body perturbation theories or density functional theory. Especially as RDM theories are non-perturbative, they are advantageous in strong coupling scenarios.

However, RDM theory was to our knowledge never applied to systems with more than one active particle type. The focus of this talk is to analyze the possibilities and problems of an extension to coupled fermion-boson theories. Comparing a typical bilinear interaction term of the form c_i⁺c_j(a_k⁺+a_k), where c⁺/c and a⁺/a indicate fermion and boson creation/annihilation operators, respectively and the fermionic 2-body interaction term c_i⁺c_j⁺c_kc_l, the former should have a considerably reduced definition space, which we hope to be exploitable. On the other hand, the bilinear interaction has a very different structure than the 2-body interaction and it is not clear at all, how to define a RDM that carries all information to compute experimental observables of a coupled fermion-boson system.

Specifically, I will illustrate some of the peculiarities of the fermion-boson interaction for simple model systems and present some ideas to deal with those.