TY - JOUR A1 - Thierschmann, H A1 - Arnold, F A1 - Mittermüller, M A1 - Maier, L A1 - Heyn, C A1 - Hansen, W A1 - Buhmann, H A1 - Molenkamp, L W T1 - Thermal gating of charge currents with Coulomb coupled quantum dots JF - New Journal of Physics N2 - We have observed thermal gating, i.e. electrostatic gating induced by hot electrons. The effect occurs in a device consisting of two capacitively coupled quantum dots. The double dot system is coupled to a hot electron reservoir on one side (QD1), while the conductance of the second dot (QD2) is monitored. When a bias across QD2 is applied we observe a current which is strongly dependent on the temperature of the heat reservoir. This current can be either enhanced or suppressed, depending on the relative energetic alignment of the QD levels. Thus, the system can be used to control a charge current by hot electrons. KW - oscillations KW - physics KW - quantum dot systems KW - Coulomb interaction KW - thermal gating KW - three terminal device KW - thermoelectrics KW - energy KW - thermopower Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-145196 VL - 17 IS - 113003 ER - TY - JOUR A1 - Sauer, C A1 - Wießner, M A1 - Schöll, A A1 - Reinert, F T1 - Observation of a molecule-metal interface charge transfer related feature by resonant photoelectron spectroscopy JF - New Journal of Physics N2 - We report the discovery of a charge transfer (CT) related low binding energy feature at a molecule-metal interface by the application of resonant photoelectron spectroscopy (RPES). This interface feature is neither present for molecular bulk samples nor for the clean substrate. A detailed analysis of the spectroscopic signature of the low binding energy feature shows characteristics of electronic interaction not found in other electron spectroscopic techniques. Within a cluster model description this feature is assigned to a particular eigenstate of the photoionized system that is invisible in direct photoelectron spectroscopy but revealed in RPES through a relative resonant enhancement. Interpretations based on considering only the predominant character of the eigenstates explain the low binding energy feature by an occupied lowest unoccupied molecular orbital, which is either realized through CT in the ground or in the intermediate state. This reveals that molecule-metal CT is responsible for this feature. Consequently, our study demonstrates the sensitivity of RPES to electronic interactions and constitutes a new way to investigate CT at molecule-metal interfaces. KW - transfer dynamics KW - photoemission KW - states KW - interface KW - charge transfer KW - organic thin films KW - resonant photoelectron spectroscopy KW - energy KW - model calculation KW - NEXAFS spectroscopy KW - ce compounds KW - absorption Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148672 VL - 17 IS - 043016 ER - TY - JOUR A1 - Kümmel, Reiner A1 - Lindenberger, Dietmar T1 - How energy conversion drives economic growth far from the equilibrium of neoclassical economics JF - New Journal of Physics N2 - Energy conversion in the machines and information processors of the capital stock drives the growth of modern economies. This is exemplified for Germany, Japan, and the USA during the second half of the 20th century: econometric analyses reveal that the output elasticity, i.e. the economic weight, of energy is much larger than energyʼs share in total factor cost, while for labor just the opposite is true. This is at variance with mainstream economic theory according to which an economy should operate in the neoclassical equilibrium, where output elasticities equal factor cost shares. The standard derivation of the neoclassical equilibrium from the maximization of profit or of time-integrated utility disregards technological constraints. We show that the inclusion of these constraints in our nonlinear-optimization calculus results in equilibrium conditions, where generalized shadow prices destroy the equality of output elasticities and cost shares. Consequently, at the prices of capital, labor, and energy we have known so far, industrial economies have evolved far from the neoclassical equilibrium. This is illustrated by the example of the German industrial sector evolving on the mountain of factor costs before and during the first and the second oil price explosion. It indicates the influence of the 'virtually binding' technological constraints on entrepreneurial decisions, and the existence of 'soft constraints' as well. Implications for employment and future economic growth are discussed. KW - economic growth KW - technological constraints KW - output elasticities KW - energy Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-118102 SN - 1367-2630 VL - 16 IS - 125008 ER - TY - JOUR A1 - Shukla, A. A1 - Mannheim, K. T1 - Gamma-ray flares from relativistic magnetic reconnection in the jet of the quasar 3C 279 JF - Nature Communications N2 - Spinning black holes in the centres of galaxies can release powerful magnetised jets. When the jets are observed at angles of less than a few degrees to the line-of-sight, they are called blazars, showing variable non-thermal emission across the electromagnetic spectrum from radio waves to gamma rays. It is commonly believed that shock waves are responsible for this dissipation of jet energy. Here we show that gamma-ray observations of the blazar 3C 279 with the space-borne telescope Fermi-LAT reveal a characteristic peak-in-peak variability pattern on time scales of minutes expected if the particle acceleration is instead due to relativistic magnetic reconnection. The absence of gamma-ray pair attenuation shows that particle acceleration takes place at a distance of ten thousand gravitational radii from the black hole where the fluid dynamical kink instability drives plasma turbulence. KW - kink instability KW - energy KW - radiation KW - blazars KW - variability KW - absorption KW - telescope KW - shocks Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-231328 VL - 11 ER - TY - JOUR A1 - Wiessner, M. A1 - Rodriguez Lastra, N. S. A1 - Ziroff, J. A1 - Forster, F. A1 - Puschnig, P. A1 - Dössel, L. A1 - Müllen, K. A1 - Schöll, A. A1 - Reinert, F. T1 - Different views on the electronic structure of nanoscale graphene: aromatic molecule versus quantum dot JF - New Journal of Physics N2 - Graphene's peculiar electronic band structure makes it of interest for new electronic and spintronic approaches. However, potential applications suffer from quantization effects when the spatial extension reaches the nanoscale. We show by photoelectron spectroscopy on nanoscaled model systems (disc-shaped, planar polyacenes) that the two-dimensional band structure is transformed into discrete states which follow the momentum dependence of the graphene Bloch states. Based on a simple model of quantum wells, we show how the band structure of graphene emerges from localized states, and we compare this result with ab initio calculations which describe the orbital structure. KW - well KW - confinement KW - states KW - Ag(111) KW - photoemission KW - vicinal surfaces KW - coronene KW - energy KW - films KW - nanographenes Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-130184 VL - 14 IS - 113008 ER -