SmB6 has recently attracted considerable interest as a candidate for the first strongly correlated topological insulator. Such materials promise entirely new properties such as correlation‐enhanced bulk bandgaps or a Fermi surface from spin excitations. Whether SmB6 and its surface states are topological or trivial is still heavily disputed however, and a solution is hindered by major disagreement between angle‐resolved photoemission (ARPES) and scanning tunneling microscopy (STM) results. Here, a combined ARPES and STM experiment is conducted. It is discovered that the STM contrast strongly depends on the bias voltage and reverses its sign beyond 1 V. It is shown that the understanding of this contrast reversal is the clue to resolving the discrepancy between ARPES and STM results. In particular, the scanning tunneling spectra reflect a low‐energy electronic structure at the surface, which supports a trivial origin of the surface states and the surface metallicity of SmB6.
Metalation and self-metalation reactions of porphyrins on oxide surfaces have recently gained interest. The mechanism of porphyrin self-metalation on oxides is, however, far from being understood. Herein, we show by a combination of results obtained with scanning tunneling microscopy, photoemission spectroscopy, and DFT computations, that the self-metalation of 2H-tetraphenylporphyrin on the surface of ultrathin MgO(001) films is promoted by charge transfer. By tuning the work function of the MgO(001)/Ag(001) substrate, we are able to control the charge and the metalation state of the porphyrin molecules on the surface.
The general decline of mountain farming all over Europe suggests encouraging farmers to adapt their farm management and to diversify their activities into tourism. Therefore, this paper aims to investigate the impact of different types of farmer-based provision of accommodation on the preservation of the farm and the identification of farmers with farming activities. For our investigation in the case study area of Ötztal valley, Tyrol, Austria, we applied a mixed method approach. First, we developed a heuristic concept for categorizing the types of farms that offer farmer-based accommodation. The term ‘farmer-based’ refers to entities who are active in accommodation services and farming. We collected quantitative data in an online survey and carried out a qualitative focus group. Results reveal the importance of farmer-based accommodation even if decoupled from farm activities within the case study area. This type also supports, next to the ‘authentic’ form of farm-based tourism, the existing agricultural structure and contributes to the positive impact of mountain farming such as for the maintenance of multifunctional cultural landscapes, the provision of ecosystem services, and the viability of rural communities. Therefore, we suggest considering decoupled forms of farmer-based accommodation as agritourism.
Recently the Many-Interacting-Worlds (MIW) approach to a quantum theory without wave functions was proposed. This approach leads quite naturally to numerical integrators of the Schrödinger equation. It has been suggested that such integrators may feature advantages over fixed-grid methods for higher numbers of degrees of freedom. However, as yet, little is known about concrete MIW models for more than one spatial dimension and/or more than one particle. In this work we develop the MIW approach further to treat arbitrary degrees of freedom, and provide a systematic study of a corresponding numerical implementation for computing one-particle ground and excited states in one dimension, and ground states in two spatial dimensions. With this step towards the treatment of higher degrees of freedom we hope to stimulate their further study.
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