Microwave zero-resistance states in a bilayer electron system

Magnetotransport measurements on a high-mobility electron bilayer system formed in a wide GaAs quantum well reveal vanishing dissipative resistance under continuous microwave irradiation. Profound zero-resistance states (ZRS) appear even in the presence of additional intersubband scattering of electrons. We study the dependence of photoresistance on frequency, microwave power. and temperature. Experimental results are compared with a theory demonstrating that the conditions for absolute negative resistivity correlate with the appearance of ZRS.Comment: 5 pages, 4 figure

Non-linear transport phenomena in a two-subband system

We study non-linear transport phenomena in a high-mobility bilayer system with two closely spaced populated electronic subbands in a perpendicular magnetic field. For a moderate direct current excitation, we observe zero-differential-resistance states with a characteristic 1/B periodicity. We investigate, both experimentally and theoretically, the Hall field-induced resistance oscillations which modulate the high-frequency magneto-intersubband oscillations in our system if we increase the current. We also observe and describe the influence of direct current on the magnetoresistance in the presence of microwave irradiation.Comment: 8 pages, 6 figure

High order fractional microwave induced resistance oscillations in 2D systems

We report on the observation of microwave-induced resistance oscillations associated with the fractional ratio n/m of the microwave irradiation frequency to the cyclotron frequency for m up to 8 in a two-dimensional electron system with high electron density. The features are quenched at high microwave frequencies independent of the fractional order m. We analyze temperature, power, and frequency dependencies of the magnetoresistance oscillations and discuss them in connection with existing theories.Comment: 5 pages, 5 figure

Microwave-induced Hall resistance in bilayer electron systems

The influence of microwave irradiation on dissipative and Hall resistance in high-quality bilayer electron systems is investigated experimentally. We observe a deviation from odd symmetry under magnetic field reversal in the microwave-induced Hall resistance $\Delta R_{xy}$ whereas the dissipative resistance $\Delta R_{xx}$ obeys even symmetry. Studies of $\Delta R_{xy}$ as a function of the microwave electric field and polarization exhibit a strong and non-trivial power and polarization dependence. The obtained results are discussed in connection to existing theoretical models of microwave-induced photoconductivity.Comment: 8 pages, 5 figure

Coexistence of electron and hole transport in graphene

When sweeping the carrier concentration in monolayer graphene through the charge neutrality point, the experimentally measured Hall resistivity shows a smooth zero crossing. Using a two- component model of coexisting electrons and holes around the charge neutrality point, we unambiguously show that both types of carriers are simultaneously present. For high magnetic fields up to 30 T the electron and hole concentrations at the charge neutrality point increase with the degeneracy of the zero-energy Landau level which implies a quantum Hall metal state at \nu=0 made up by both electrons and holes.Comment: 5 pages, 6 figure

Probing the surface states in Bi2Se3 using the Shubnikov-de Haas effect

Shubnikov-de Haas (SdH) oscillations are observed in Bi2Se3 flakes with high carrier concentration and low bulk mobility. These oscillations probe the protected surface states and enable us to extract their carrier concentration, effective mass and Dingle temperature. The Fermi momentum obtained is in agreement with angle resolved photoemission spectroscopy (ARPES) measurements performed on crystals from the same batch. We study the behavior of the Berry phase as a function of magnetic field. The standard theoretical considerations fail to explain the observed behavior.Comment: 6 pages, 8 figures. Accepted to Physical Review

Shedding New Light on Kaon-Nucleon/Nuclei Interaction and Its Astrophysical Implications with the AMADEUS Experiment at DAFNE

The AMADEUS experiment deals with the investigation of the low-energy kaon-nuclei hadronic interaction at the DA{\Phi}NE collider at LNF-INFN, which is fundamental to respond longstanding questions in the non-perturbative QCD strangeness sector. The antikaon-nucleon potential is investigated searching for signals from possible bound kaonic clusters, which would open the possibility for the formation of cold dense baryonic matter. The confirmation of this scenario may imply a fundamental role of strangeness in astrophysics. AMADEUS step 0 consisted in the reanalysis of 2004/2005 KLOE dataset, exploiting K- absorptions in H, 4He, 9Be and 12C in the setup materials. In this paper, together with a review on the multi-nucleon K- absorption and the particle identification procedure, the first results on the {\Sigma}0-p channel will be presented including a statistical analysis on the possible accomodation of a deeply bound stateComment: 6 pages, 2 figure, 1 table, HADRON 2015 conferenc

A Self-administered version of the functioning assessment short test for use in population-based studies: A pilot study

Background: The Functioning Assessment Short Test (FAST) is an interviewer-administered scale assessing functional impairment originally developed for psychiatric patients. Objectives: To adapt the FAST for the general population, we developed a self-administered version of the scale and assessed its properties in a pilot study. Methods: The original FAST scale was translated into German via forward and backward translation. Afterwards, we adjusted the scale for self-administered application and inquired participants from two ongoing studies in Germany, 'STAAB' (Würzburg) and 'BiDirect' (Münster), both recruiting subjects from the general population across a wide age range (STAAB: 30-79 years, BiDirect: 35-65 years). To assess reliability, agreement of self-assessment with proxy-assessment by partners was measured via intraclass correlation coefficient (ICC) over the FAST score. Construct validity was estimated by conducting correlations with validated scales of depression (PHQ-9), anxiety (GAD-7), and health-related quality of life (SF-12) and regression analyses using these scales besides potentially disabling comorbidities (e.g. Chronic Back Pain (CBP)). Results: Participants (n=54) had a median age of 57.0 years (quartiles: 49.8, 65.3), 46.3% were female. Reliability was moderate: ICC 0.50 (95% CI 0.46-0.54). The FAST score significantly correlated with PHQ-9, GAD-7, and the mental sub-scale of SF-12. In univariable linear regression, all three scales and chronic back pain explained variance of the FAST score. In multivariable analysis, only CBP and the SF-12 remained significant predictors. Conclusion: The German self-administered version of the FAST yielded moderate psychometric properties in this pilot study, indicating its applicability to assess functional impairment in the general population

A new integrated power plant with a small scale turbine for the Organic Rankine Cycle

Combined heat and power (CHP or cogeneration) describes the simultaneous generation of electrical power and heat. CHP has been well established for medium and high power ranges (> 100 kW el. power). The Kompakte Dampf Turbine (KDT, meaning compact steam turbine) addresses the low-end of power generation (~2 kW el. power). The KDT is a highly integrated power plant of small dimensions able to use various heat sources. Its simple design promises a low-cost CHP for residential homes

Implementing the material footprint to measure progress towards Sustainable Development Goals 8 and 12

Sustainable development depends on decoupling economic growth from resource use. The material footprint indicator accounts for environmental pressure related to a country’s final demand. It measures material use across global supply-chain networks linking production and consumption. For this reason, it has been used as an indicator for two Sustainable Development Goals: 8.4 ‘resource efficiency improvements’ and 12.2 ‘sustainable management of natural resources’. Currently, no reporting facility exists that provides global, detailed and timely information on countries’ material footprints. We present a new collaborative research platform, based on multiregional input–output analysis, that enables countries to regularly produce, update and report detailed global material footprint accounts and monitor progress towards Sustainable Development Goals 8.4 and 12.2. We show that the global material footprint has quadrupled since 1970, driven mainly by emerging economies in the Asia-Pacific region, but with an indication of plateauing since 2014. Capital investments increasingly dominate over household consumption as the main driver. At current trends, absolute decoupling is unlikely to occur over the next few decades. The new collaborative research platform allows to elevate the material footprint to Tier I status in the SDG indicator framework and paves the way to broaden application of the platform to other environmental footprint indicators