AFM probe for the signatures of Wigner correlations in the conductance of a one-dimensional quantum dot

The transport properties of an interacting one-dimensional quantum dot capacitively coupled to an atomic force microscope probe are investigated. The dot is described within a Luttinger liquid framework which captures both Friedel and Wigner oscillations. In the linear regime, we demonstrate that both the conductance peak position and height oscillate as the tip is scanned along the dot. A pronounced beating pattern in the conductance maximum is observed, connected to the oscillations of the electron density. Signatures of the effects induced by a Wigner molecule are clearly identified and their stability against the strength of Coulomb interactions are analyzed. While the oscillations of the peak position due to Wigner get enhanced at strong interactions, the peak height modulations are suppressed as interactions grow. Oscillations due to Friedel, on the other hand, are robust against interaction.Comment: 9 figure

Probing Wigner correlations in a suspended carbon nanotube

The influence of the electron-vibron coupling on the transport properties of a strongly interacting quantum dot built in a suspended carbon nanotube is analyzed. The latter is probed by a charged AFM tip scanned along the axis of the CNT which induces oscillations of the chemical potential and of the linear conductance. These oscillations are due to the competition between finite-size effects and the formation of a Wigner molecule for strong interactions. Such oscillations are shown to be suppressed by the electron-vibron coupling. The suppression is more pronounced in the regime of weak Coulomb interactions, which ensures that probing Wigner correlations in such a system is in principle possible

Theory of the STM detection of Wigner molecules in spin incoherent CNTs

The linear conductance of a carbon nanotube quantum dot in the Wigner molecule regime, coupled to two scanning tunnel microscope tips is inspected. Considering the high temperature regime, the nanotube quantum dot is described by means of the spin-incoherent Luttinger liquid picture. The linear conductance exhibits spatial oscillations induced by the presence of the correlated, molecular electron state. A power-law scaling of the electron density and of the conductance as a function of the interaction parameter are found. They confirm local transport as a sensitive tool to investigate the Wigner molecule. The double-tip setup allows to explore different transport regimes with different shapes of the spatial modulation, all bringing information about the Wigner molecule

Temperature-induced emergence of Wigner correlations in a STM-probed one-dimensional quantum dot

The temperature-induced emergence of Wigner correlations over finite-size effects in a strongly interacting one-dimensional quantum dot are studied in the framework of the spin coherent Luttinger liquid. We demonstrate that, for temperatures comparable with the zero mode spin excitations, Friedel oscillations are suppressed by the thermal fluctuations of higher spin modes. On the other hand, the Wigner oscillations, sensitive to the charge mode only, are stable and become more visible. This behavior is proved to be robust both in the thermal electron density and in the linear conductance in the presence of an STM tip. This latter probe is not directly proportional to the electron density and may confirm the above phenomena with complementary and additional information

Correlation functions for the detection of Wigner molecules in a one-channel Luttinger liquid quantum dot

In one-channel, finite-size Luttinger one-dimensional quantum dots, both Friedel oscillations and Wigner correlations induce oscillations in the electron density with the same wavelength, pinned at the same position. Therefore, observing such a property does not provide any hint about the formation of a Wigner molecule when electrons interact strongly and other tools must be employed to assess the formation of such correlated states. We compare here the behavior of three different correlation functions and demonstrate that the integrated two point correlation function, which represents the probability density of finding two particles at a given distance, is the only faithful estimator for the formation of a correlated Wigner molecule.Comment: 6 pages, 5 figure

Carbon nanotube sensor for vibrating molecules

The transport properties of a CNT capacitively coupled to a molecule vibrating along one of its librational modes are studied and its transport properties analyzed in the presence of an STM tip. We evaluate the linear charge and thermal conductances of the system and its thermopower. They are dominated by position-dependent Franck-Condon factors, governed by a position-dependent effective coupling constant peaked at the molecule position. Both conductance and thermopower allow to extract some information on the position of the molecule along the CNT. Crucially, however, thermopower sheds also light on the vibrational levelspacing, allowing to obtain a more complete characterization of the molecule even in the linear regime

Life cycle approach to sustainability assessment : a case study of remanufactured alternators

Sustainability is an international issue with increasing concern and becomes a crucial driver for the industry in international competition. Sustainability encompasses the three dimensions: environment, society and economy. This paper presents the results from a sustainability assessment of a product. To prevent burden shifting, the whole life cycle of the products is necessary to be taken into account. For the environmental dimension, life cycle assessment (LCA) has been practiced for nearly 40 years and is the only one standardised by the International Organization for Standardization (ISO) (14040 and 14044). Life cycle approaches for the social and economic dimensions are currently under development. Life cycle sustainability assessment (LCSA) is a complementary implementation of the three techniques: LCA (environmental), life cycle costing (LCC - economic) and social LCA (SLCA - social). This contribution applies the state-of-the-art LCSA on remanufacturing of alternators aiming at supporting managers and product developers in their decision-making to design product and plant. The alternator is the electricity generator in the automobile vehicle which produces the needed electricity. LCA and LCC are used to assess three different alternator design scenarios (namely conventional, lightweight and ultra-lightweight). The LCA and LCC results show that the conventional alternator is the most promising one. LCSA of three different locations (Germany, India and Sierra Leone) for setting the remanufacturing mini-factory, a worldwide applicable container, are investigated on all three different sustainability dimensions: LCA, LCC and SLCA. The location choice is determined by the SLCA and the design alternatives by the LCA and LCC. The case study results show that remanufacturing potentially causes about 12% of the emissions and costs compared to producing new parts. The conventional alternator with housing of iron cast performs better in LCA and LCC than the lightweight alternatives with aluminium housing. The optimal location of remanufacturing is dependent on where the used alternators are sourced and where the remanufactured alternators are going to be used. Important measures to improve the sustainability of the remanufacturing process in life cycle perspective are to confirm if the energy efficiency of the remanufactured part is better than the new part, as the use phase dominates from an environmental and economical point of view. The SLCA should be developed further, focusing on the suitable indicators and conducting further case studies including the whole life cycle

АВТОМАТИЗОВАНА КОМПОЗИЦІЯ СЕМАНТИЧНИХ ВЕБ-СЕРВІСІВ У ВИКОНУВАНІ ПРОЦЕСИ. ПЕРЕКЛАД СТАТТІ «AUTOMATED COMPOSITION OF SEMANTIC WEB SERVICES INTO EXECUTABLE PROCESSES\ud (ПЕРЕКЛАД РЕМАРОВИЧ С.)\ud

Пропонується метод планування для автоматизованої композиції Веб-сервісів, які описані в OWL-S моделях процесу, який може\ud ефективно боротися з недетермінізмом, частковою спостережністю і складними цілями.\ud \ud Abstract\ud Different planning techniques have been applied to the problem of automated composition of web services. However, in realistic cases, this planning problem is far from trivial: the planner needs to deal with the nondeterministic behavior of web services, the partial observability of their internal status, and with complex goals expressing temporal conditions and preference requirements. We propose a planning technique for the automated composition of web services described in OWL-S process models, which can deal effectively with nondeterminism, partial observability, and complex goals. The technique allows for the synthesis of plans that encode compositions of web services with the usual programming constructs, like conditionals and iterations. The generated plans can thus be translated into executable processes, e.g., BPEL4WS programs. We implement our solution in a planner and do some preliminary experimental evaluations that show the potentialities of our approach, and the gain in performance of automating the composition at the semantic level w.r.t. the automated composition at the level of executable processes

Inelastic and elastic collision rates for triplet states of ultracold strontium

We report measurement of the inelastic and elastic collision rates for ^{88}Sr atoms in the (5s5p)^3P_0 state in a crossed-beam optical dipole trap. This is the first measurement of ultracold collision properties of a ^3P_0 level in an alkaline-earth atom or atom with similar electronic structure. Since the (5s5p)^3P_0 state is the lowest level of the triplet manifold, large loss rates indicate the importance of principle-quantum-number-changing collisions at short range. We also provide an estimate of the collisional loss rates for the (5s5p){^3P_2} state.Comment: 4 pages 5 figure