Dynamical mean-field theory for molecules and nanostructures

Abstract

Dynamical Mean-Field Theory (DMFT) has established itself as a reliable and well-controlled approximation to study correlation effects in bulk solids and also two-dimensional systems. In combination with standard density-functional theory (DFT) it has been successfully applied to study materials in which localized electronic states play an important role. There are several evidences that for extended systems this DMFT+DFT approach is more accurate than the traditional DFT+U approximation, particularly because of its ability to take into account dynamical effects, such as the time-resolved double occupancy of the electronic orbitals. It was recently shown that this approach can also be successfully applied to study correlation effects in nanostructures. Here, we present a brief review of the recently proposed generalizations of the DFT+DMFT method. In particular, we discuss in details our recently proposed DFT+DMFT approach to study the magnetic properties of nanosystems[1] and present its application to small (up to five atoms) Fe andFePt clusters. We demonstrate that being a mean-field approach, DMFT produces meaningful results even for such small systems. We compare our results with those obtained using DFT+U and find that, as in the case of bulk systems, the latter approach tends to overestimate correlation effects in nanostructures. Finally, we discuss possible ways to farther improve the nano-DFT+DMFT approximation and to extend its application to molecules and nanoparticles on substrates and to nonequilibrium phenomena.

Interaction-induced local moments in parallel quantum dots within the functional renormalization group approach

“…The recently prposed nanoscopic dynamic vertex approximation (nano-DΓA) [19,20], allows one to treat effects of interaction in nanostructures, and has a potential of describing non-local correlations beyond nano-DMFT [21][22][23][24][25]. In the most complete, parquete, formulation nano-DΓA approach however also requires substantial computational resources.…”

Functional renormalization group study of parallel double quantum dots: Effects of asymmetric dot-lead couplings

“…Numerical efforts, which are necessary for the existing numerical methods (e.g., numerical renormalization group (NRG) [39], quantum Monte Carlo [40,41], continuous-time quantum Monte Carlo [42], exact diagonalization [43][44][45], nano-DMFT [46][47][48][49][50][51], and nano-DΓA [48,52]) grow fast with increasing system size or asymmetry, such that the comprehensive analysis of complex quantum dot systems (especially the conductance) is rather difficult for purely numerical methods. Therefore, developing and using semi-analytical techniques is important for description of such systems.…”

Realistic theory of electronic correlations in nanoscopic systems

“…2 Interface of density functional and dynamical mean field theory for the simulation of complex structures Considerable efforts have been focussed on the modelling of correlated nanoscale systems using DMFT techniques, e.g., [5][6][7][8][9][10][11][12][13][14][15][16]. Here, we describe the approach to a material realistic DMFT scheme for nanosystems which has been implemented by the authors during the course of FOR 1346, and which is particularly flexible.…”