Abstract

In this talk I will describe two examples of application of topology tophysics. The first one refers to attempts to understand the spin-statisticsconnection in the non-relativistic context. This naturally leads to theconsideration of quantum mechanics on topologically non-trivialconfigurations spaces. The second one has to do with the possibility ofrelating certain topological invariants to quantum systems that present aquantum phase transition. In particular I will show how, in the case of theanisotropic XY-model, it is possible to actually compute these invariantsand relate their dependence on the external field to the quantum phasetransition.

Abstract

Abstract

Self-organized growth of surface supported nano-structures like atomic nanowires are likely to play important role in future electronic devices where the confined electrons show quantization phenomena. The formation and growth behavior of epitaxial atomic nanowires of 3d, 4d and 5d elements on a corrugated molecular Cu3N network on a Cu(110) surface have been reported. An element independent growth of nanowires consisting of 5 atomic rows (~ 1 nm in width) running along [1-10] direction on Cu3N-Cu(110) surface was observed [1]. The charge density of Cu(110) surface can be dramatically altered by terminating the surface with a (2×3) copper nitride (Cu3N) layer. A proper understanding of the local electronic properties of the corrugated Cu3N-Cu(110) molecular network and the atomic nanowires grown on this surface would be fundamentally important. We report here the low temperature (4.7 K) scanning tunneling spectroscopy (LT-STS) studies of both the Cu3N layer and the Cu, Fe & Au atomic nanowires grown at room temperature on this surface. Constant height and constant current spectroscopy measurements have been carried out on the Cu3N network and on the atomic nanowires. LT-STS studies on the Cu3N surface show three unoccupied electronic states at 2.0 V, 3.4 V and 4.0 V and two occupied electronic states at -5.6 V and -8.0 V. These results are qualitatively understood as various hybridized N 2p Cu 3d states [2]. Tunneling spectroscopy measurements performed on the atomic nanowires of Cu, Fe & Au show appearance of two pronounced unoccupied electronic states at ~ 1.8 V and ~ 3.8 V. These observations will be discussed in view of the electronic structure of the Cu/Fe/Au-Cu3N-Cu(110) system.[1] X.-D. Ma, D. I. Bazhanov, O. Fruchart, F.Yildiz, T.Yokoyama, M.Przybylski, V.Stepanyuk, W. Hergert and J.Kirschner. PRL 102, 205503 (2009)[2] K. Bhattacharjee, X. –D. Ma, Y. Zhang, M. Przybylski and J. Kirschner, accepted Surf. Sci., doi: 10.1016/j.susc. 2011.12.002

Abstract

Abstract

Green sulfur bacteria are a kind of bacteria that are present in lakes and near deep-sea thermal vents. The Fenna-Matthews-Olson (FMO) complex is a molecular complex that is central to the transfer of light trapped by a light-harvesting antenna to the interior of the cell for photosynthetic activity. There has been some experimental work suggesting that the transfer of excitations across the FMO complex is mediated by quantum correlations. We will investigate quantum correlations in such complexes with a focus on measures of entanglement and other correlations.