Extracting the Transport Channel Transmissions in Scanning Tunneling Microscopy using the Superconducting Excess Current

Transport through quantum coherent conductors, like atomic junctions, is described by the distribution of conduction channels. Information about the number of channels and their transmission can be extracted from various sources, such as multiple Andreev reflections, dynamical Coulomb blockade, or shot noise. We complement this set of methods by introducing the superconducting excess current as a new tool to continuously extract the transport channel transmissions of an atomic scale junction in a scanning tunneling microscope. In conjunction with ab initio simulations, we employ this technique in atomic aluminum junctions to determine the influence of the structure adjacent to the contact atoms on the transport properties.Comment: 8 pages, 9 figures, including supporting informatio

Extracting transport channel transmissions in scanning tunneling microscopy using superconducting excess current

Transport through quantum coherent conductors, such as atomic junctions, is described by conduction channels. Information about the number of channels and their transmissions can be extracted from various sources, such as multiple Andreev reflections, dynamical Coulomb blockade, or shot noise. We complement this set of methods by introducing the superconducting excess current as a new tool to continuously extract the transport channel transmissions of an atomic scale junction in a scanning tunneling microscope. In conjunction with ab initio simulations, we employ this technique in atomic aluminum junctions to determine the influence of the structure adjacent to the contact atoms on the transport propertie

Addressing climate change with behavioral science: a global intervention tournament in 63 countries

Effectively reducing climate change requires marked, global behavior change. However, it is unclear which strategies are most likely to motivate people to change their climate beliefs and behaviors. Here, we tested 11 expert-crowdsourced interventions on four climate mitigation outcomes: beliefs, policy support, information sharing intention, and an effortful tree-planting behavioral task. Across 59,440 participants from 63 countries, the interventions’ effectiveness was small, largely limited to nonclimate skeptics, and differed across outcomes: Beliefs were strengthened mostly by decreasing psychological distance (by 2.3%), policy support by writing a letter to a future-generation member (2.6%), information sharing by negative emotion induction (12.1%), and no intervention increased the more effortful behavior—several interventions even reduced tree planting. Last, the effects of each intervention differed depending on people’s initial climate beliefs. These findings suggest that the impact of behavioral climate interventions varies across audiences and target behaviors

Transmission eigenchannels for coherent phonon transport

We present a procedure to determine transmission eigenchannels for coherent phonon transport in nanoscale devices using the framework of nonequilibrium Green's functions. We illustrate our procedure by analyzing a one-dimensional chain, where all steps can be carried out analytically. More importantly, we show how the procedure can be combined with ab initio calculations to provide a better understanding of phonon heat transport in realistic atomic-scale junctions. In particular, we study the phonon eigenchannels in a gold metallic atomic-size contact and different single-molecule junctions based on molecules such as an alkane chain, a brominated benzene-diamine, where destructive phonon interference effects take place, and a C60 junction.publishe

Tuning the thermal conductance of molecular junctions with interference effects

We present an ab initio study of the role of interference effects in the thermal conductance of single-molecule junctions. To be precise, using a first-principles transport method based on density functional theory, we analyze the coherent phonon transport in single-molecule junctions made of several benzene and oligo(phenylene ethynylene) derivatives. We show that the thermal conductance of these junctions can be tuned via the inclusion of substituents, which induces destructive interference effects and results in a decrease of the thermal conductance with respect to the unmodified molecules. In particular, we demonstrate that these interference effects manifest as antiresonances in the phonon transmission, whose energy positions can be tuned by varying the mass of the substituents. Our work provides clear strategies for the heat management in molecular junctions and, more generally, in nanostructured metal-organic hybrid systems, which are important to determine how these systems can function as efficient energy-conversion devices such as thermoelectric generators and refrigerators.publishe

Length dependence of the thermal conductance of alkane-based single-molecule junctions : an ab-initio study

Motivated by recent experiments, we present here a systematic ab-initio study of the length dependence of the thermal conductance of single-molecule junctions. We make use of a combination of density functional theory with non-equilibrium Green's function techniques to investigate the length dependence of the phonon transport in single alkane chains, contacted with gold electrodes via both thiol and amine anchoring groups. Additionally, we study the effect of the substitution of the hydrogen atoms in the alkane chains by heavier fluorine atoms to form polytetrafluoroethylenes. Our results demonstrate that (i) the room-temperature thermal conductance is fairly length-independent for chains with more than 5 methylene units and (ii) the efficiency of the thermal transport is strongly influenced by the strength of the phononic metal-molecule coupling. Our study sheds new light onto the phonon transport in molecular junctions, and it provides clear guidelines for the design of molecular junctions for thermal management.publishe

How do Swiss medical schools prepare their students to become good communicators in their future professional careers: a questionnaire and interview study involving medical graduates, teachers and curriculum coordinators

BACKGROUND Since 2011, the Swiss Catalogue of Learning Objectives (SCLO) has provided the framework for assessing communication skills in the Swiss Medical Federal Licensing Examination (FLE). This study evaluates how far the communication curricula of five Swiss medical schools match the SCLO and international recommendations. It also explores their strengths, weaknesses, opportunities and threats (SWOT). METHODS A mixed method approach was used. In a first step, curriculum coordinators/key communication skills teachers and medical graduates were asked to fill out a questionnaire based on communication related objectives from the SCLO and a review of European consensus statements on communication training. Second, information was collected from all Swiss medical schools to identify which communication skills were taught in which formats and at what time points within the 6-year curricula. Finally, 3-4 curriculum coordinators/key communication skills teachers from each medical school were interviewed about their communication curriculum, using SWOT analysis. RESULTS Sixteen teachers/coordinators (response rate 100%) and 389 medical graduates (response rate 43%) filled out the questionnaire. Both the teachers/coordinators and the graduates considered that two thirds of the communication items listed in the questionnaire were covered in their curricula. Between sixty and two hundred structured hours were dedicated to communication, predominantly in small group and experiential formats. Assessment relied on both MCQs and OSCEs. Most of the training occurred during the first three years of medical school. Teachers felt that the need for communication skills training was now well-recognized by their institution and was taught with appropriate teaching methods. However, recruitment and training of teachers, continuity of communication skills training during clinical years, and the adoption of a common frame of reference among the five medical schools, remained a challenge. CONCLUSION Although the Swiss medical schools all offered a partly longitudinal communication skills training, with appropriate teaching methods, this study indicates that the communication skills actually taught do not fully match the SCLO or international recommendations. There was less training for complex communication skills training during the clinical years, and ensuring quality and coherence in the teaching remained a challenge

Thermal conductance of single-molecule junctions

Single-molecule junctions have been extensively used to probe properties as diverse as electrical conduction, light emission, thermoelectric energy conversion, quantum interference, heat dissipation and electronic noise at atomic and molecular scales. However, a key quantity of current interest???the thermal conductance of single-molecule junctions???has not yet been directly experimentally determined, owing to the challenge of detecting minute heat currents at the picowatt level. Here we show that picowatt-resolution scanning probes previously developed to study the thermal conductance of single-metal-atom junctions, when used in conjunction with a time-averaging measurement scheme to increase the signal-to-noise ratio, also allow quantification of the much lower thermal conductance of single-molecule junctions. Our experiments on prototypical Au???alkanedithiol???Au junctions containing two to ten carbon atoms confirm that thermal conductance is to a first approximation independent of molecular length, consistent with detailed ab initio simulations. We anticipate that our approach will enable systematic exploration of thermal transport in many other one-dimensional systems, such as short molecules and polymer chains, for which computational predictions of thermal conductance have remained experimentally inaccessible