New Ways through the Alps The New Gotthard Base Tunnel - Impact of a Big Construction Site on a Small Mountain Village

For Switzerland as located in the heart of Europe transport policy is a matter of particular importance. Especially transports between Italy and Germany use the Swiss corridors through the Alps. Therefore Switzerland realised a most ambitious construction project called NEAT (Neue Alpen Transversale) to improve the European train connections especially for freight transports. One part of the project is the new Gotthard base tunnel, the longest railway tunnel of the world and the most impressive element of the new transalpine railway line through the Alps. In view of the difficult accessibility and extreme climatic conditions, ensuring the fast and reliable transit of more than 300 trains per day through the two 57 km long single-track galleries represents a considerable technical challenge. The Gotthard base line directly links the northern and southern sides of the Alps and the project of building a new line should achieve the following goals: Massive increase in goods capacity (twice as much as today) Much shorter North-South transit time for passengers and freight Reduced traction power requirements, per weight unit of transported goods, as a result of the elimination of steep slopes. The construction work started in 1996 and will be probably finished by 2013. Because of the length of the tunnel five points were chosen, from which the drilling started. The shortest but technical most challenging phase of construction is located under the small village of “Sedrun” in the canton of “Graubünden”. Sedrun is a tourism destination for skiing, 1335 m above sea level with about 1.500 inhabitants. Here a gallery leads to a mine shaft with a depth of 800 m, ending at 550 m above sea level. At the intermediate access of Sedrun a multifunctional station is located which also is used for crossover, air ventilation, technical infrastructure and in case of emergency. The construction site with its enormous needs on resources, infrastructure, workforces - for example at the beginning a lot of specialists from South African mining branch came to Sedrun – may be a big challenge for the small village. In 2004 during the peak period up to 400 workers have been employed. Also logistical solutions for the transport of machines and material to the construction side and the carrying of stone to the deposits have to be developed. An ongoing long-term accompanying research (2000 – 2013) is analysing the ecological, economic and social impact on the construction site for the village and the region. The research project wants to assess the sustainability of such a long-term construction process. The contracting body is an advisory group of public institutions including the community of Sedrun, the region ‘Obere Surselva’, the canton Graubünden and the Swiss Federal Office of Transport. Within the long-term research a set of indicators will be collected every year furthermore an every third year deep-rooted analysis on different topics will be done. The project also has the function of an early-warning system to anticipate unexpected stresses and strains. The results of the research will be visualised from a documentary film team. Besides the annual research we tried to answer the following question: Which are the economic impacts of the construction site for the region of Sedrun? The decision to choose Sedrun as one of the five construction sites for the Gotthard base tunnel did not only change the ecological and social situation in the region but also has economic effects on the community. Especially the local building sector but also hotels, restaurants and local industry are benefiting from the construction site. To calculate these economic effects for the region of Sedrun we used the method of the incidence analysis. The incidence analysis is a kind of cost-benefit analysis which is especially suited to assess the spatial effects of infrastructural facilities or the service of these facilities. Considering the direct effects we focus on the receipts and expenditures which are directly connected with the realisation of the project. The economic effects could be divided into the so called tangible and intangible effects. Tangible effects are measurable as indirect economic effects (spill-over effects). To measure the indirect economic effects we carry out an interview survey among the workers to calculate the additional economic impacts caused by the expenditures of the workers in the region. The intangible effects could be explained as soft and mostly not quantifiable effects. To acquire the intangible effects we carry out an image analysis based on national newspaper articles about the construction site in Sedrun. In our paper we present the structure and main indicators of the long-term accompanying research and the results of the incidence analysis to calculate the economic effects for the region.

Aperiodic conductivity oscillations in quasi-ballistic graphene heterojunctions

We observe conductivity oscillations with aperiodic spacing to only one side of the tunneling current in a dual-gated graphene field effect transistor with an n-p-n type potential barrier. The spacing and width of these oscillatoins were found to be inconsistent with pure Farbry-Perot-type interferences, but are in quantitative agreement with theoretical predictions that attribute them to resonant tunneling through quasi-bound impurity states. This observation may be understood as another signature of Klein tunneling in graphene heterojunctions and is of importance for future development and modeling of graphene based nanoelectronic devices.Comment: 3 pages, 3 figure

Transconductance and Coulomb blockade properties of in-plane grown carbon nanotube field effect transistors

Single electron transistors (SETs) made from single wall carbon nanotubes (SWCNTs) are promising for quantum electronic devices operating with ultra-low power consumption and allow fundamental studies of electron transport. We report on SETs made by registered in-plane growth utilizing tailored nanoscale catalyst patterns and chemical vapor deposition. Metallic SWCNTs have been removed by an electrical burn-in technique and the common gate hysteresis was removed using PMMA and baking, leading to field effect transistors with large on/off ratios up to 10^5. Further segmentation into 200 nm short semiconducting SWCNT devices created quantum dots which display conductance oscillations in the Coulomb blockade regime. The demonstrated utilization of registered in-plane growth opens possibilities to create novel SET device geometries which are more complex, i.e. laterally ordered and scalable, as required for advanced quantum electronic devices.Comment: 15 pages, 4 figure

Localized States and Resultant Band Bending in Graphene Antidot Superlattices

We fabricated dye sensitized graphene antidot superlattices with the purpose of elucidating the role of the localized edge state density. The fluorescence from deposited dye molecules was found to strongly quench as a function of increasing antidot filling fraction, whereas it was enhanced in unpatterned but electrically back-gated samples. This contrasting behavior is strongly indicative of a built-in lateral electric field that accounts for fluorescence quenching as well as p-type doping. These findings are of great interest for light-harvesting applications that require field separation of electron-hole pairs.Comment: NanoLetters, 201

Photon statistics from coupled quantum dots

We present an optical study of closely-spaced self-assembled InAs/GaAs quantum dots. The energy spectrum and correlations between photons subsequently emitted from a single pair provide not only clear evidence of coupling between the quantum dots but also insight into the coupling mechanism. Our results are in agreement with recent theories predicting that tunneling is largely suppressed between nonidentical quantum dots and that the interaction is instead dominated by dipole-dipole coupling and phonon-assisted energy transfer processes.Comment: 4 pages, 4 figures, to appear in Phys. Re

Determination of Edge Purity in Bilayer Graphene Using micro-Raman Spectroscopy

Polarization resolved micro-Raman spectroscopy was carried out at the edges of bilayer graphene. We find strong dependence of the intensity of the G band on the incident laser polarization, with its intensity dependence being 90 degrees out of phase for the armchair and zigzag case, in accordance with theoretical predictions. For the case of mixed-state edges we demonstrate that the polarization contrast reflects the fractional composition of armchair and zigzag edges, providing a monitor of edge purity, which is an important parameter for the development of efficient nanoelectronic devices.Comment: 3 pages, 3 figures, to appear in Applied Physics Letter

Trion Species-Resolved Quantum Beats in MoSe2

Monolayer photonic materials offer a tremendous potential for on-chip optoelectronic devices. Their realization requires knowledge of optical coherence properties of excitons and trions that have so far been limited to nonlinear optical experiments carried out with strongly inhomogenously broadened material. Here we employ h-BN encapsulated and electrically gated MoSe2 to reveal coherence properties of trion-species directly in the linear optical response. Autocorrelation measurements reveal long dephasing times up to T2=1.16+-0.05 ps for positively charged excitons. Gate dependent measurements provide evidence that the positively-charged trion forms via spatially localized hole states making this trion less prone to dephasing in the presence of elevated hole carrier concentrations. Quantum beat signatures demonstrate coherent coupling between excitons and trions that have a dephasing time up to 0.6 ps, a two-fold increase over those in previous reports. A key merit of the prolonged exciton/trion coherences is that they were achieved in a linear optical experiment, and thus are directly relevant to applications in nanolasers, coherent control, and on-chip quantum information processing requiring long photon coherence.Comment: 21 pages, 6 figures, 2 SOI figure