Project acronym COSPSENA
Project Coherence of Spins in Semiconductor Nanostructures
Researcher (PI) Dominik Max Zumbühl
Host Institution (HI) UNIVERSITAT BASEL
Call Details Starting Grant (StG), PE3, ERC-2007-StG
Summary Macroscopic control of quantum states is a major theme in much of modern physics because quantum coherence enables study of fundamental physics and has promising applications for quantum information processing. The potential significance of quantum computing is recognized well beyond the physics community. For electron spins in GaAs quantum dots, it has become clear that decoherence caused by interactions with the nuclear spins is a major challenge. We propose to investigate and reduce hyperfine induced decoherence with two complementary approaches: nuclear spin state narrowing and nuclear spin polarization. We propose a new projective state narrowing technique: a large, Coulomb blockaded dot measures the qubit nuclear ensemble, resulting in enhanced spin coherence times. Further, mediated by an interacting 2D electron gas via hyperfine interaction, a low temperature nuclear ferromagnetic spin state was predicted, which we propose to investigate using a quantum point contact as a nuclear polarization detector. Estimates indicate that the nuclear ferromagnetic transition occurs in the sub-Millikelvin range, well below already hard to reach temperatures around 10 mK. However, the exciting combination of interacting electron and nuclear spin physics as well as applications in spin qubits give ample incentive to strive for sub-Millikelvin temperatures in nanostructures. We propose to build a novel type of nuclear demagnetization refrigerator aiming to reach electron temperatures of 0.1 mK in semiconductor nanostructures. This interdisciplinary project combines Microkelvin and nanophysics, going well beyond the status quo. It is a challenging project that could be the beginning of a new era of coherent spin physics with unprecedented quantum control. This project requires a several year commitment and a team of two graduate students plus one postdoctoral fellow.
Summary
Macroscopic control of quantum states is a major theme in much of modern physics because quantum coherence enables study of fundamental physics and has promising applications for quantum information processing. The potential significance of quantum computing is recognized well beyond the physics community. For electron spins in GaAs quantum dots, it has become clear that decoherence caused by interactions with the nuclear spins is a major challenge. We propose to investigate and reduce hyperfine induced decoherence with two complementary approaches: nuclear spin state narrowing and nuclear spin polarization. We propose a new projective state narrowing technique: a large, Coulomb blockaded dot measures the qubit nuclear ensemble, resulting in enhanced spin coherence times. Further, mediated by an interacting 2D electron gas via hyperfine interaction, a low temperature nuclear ferromagnetic spin state was predicted, which we propose to investigate using a quantum point contact as a nuclear polarization detector. Estimates indicate that the nuclear ferromagnetic transition occurs in the sub-Millikelvin range, well below already hard to reach temperatures around 10 mK. However, the exciting combination of interacting electron and nuclear spin physics as well as applications in spin qubits give ample incentive to strive for sub-Millikelvin temperatures in nanostructures. We propose to build a novel type of nuclear demagnetization refrigerator aiming to reach electron temperatures of 0.1 mK in semiconductor nanostructures. This interdisciplinary project combines Microkelvin and nanophysics, going well beyond the status quo. It is a challenging project that could be the beginning of a new era of coherent spin physics with unprecedented quantum control. This project requires a several year commitment and a team of two graduate students plus one postdoctoral fellow.
Max ERC Funding
1 377 000 €
Duration
Start date: 2008-06-01, End date: 2013-05-31
Project acronym ELNOX
Project Elemental nitrogen oxidation – A new bacterial process in the nitrogen cycle
Researcher (PI) Heide Schulz-Vogt
Host Institution (HI) MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Call Details Starting Grant (StG), PE8, ERC-2007-StG
Summary The largest reservoir for nitrogen on earth is the atmosphere that contains 78 percent nitrogen gas. Until now the only known biological process interacting with elemental nitrogen is the bacterial reduction of nitrogen to ammonia for the build up of biomass (nitrogen fixation). This reaction requires energy and is only carried out in the absence of other nitrogen sources, such as ammonia or nitrate. Thermodynamically, the oxidation of nitrogen to nitrate with oxygen releases reasonable amounts of energy, but no bacterium using this redox couple has been known until today. We have isolated a marine bacterium, which is capable of growing in the dark with nitrogen gas as electron donor and oxygen as electron acceptor while forming nitrate. As this microorganism can also use carbondioxide as a carbon source it basically lives of air. While oxidizing atmospheric nitrogen gas the bacterium releases large amounts of nitrate and thereby enhances the amount of fixed nitrogen available for other organisms. At the moment the apparent flux of elemental nitrogen to the ocean by bacterial nitrogen fixation is much smaller than the loss of nitrogen through bacterial denitrification, suggesting that we are missing a major input of nitrogen. This newly discovered physiology of nitrogen oxidation could close this large gap in our understanding of the nitrogen cycle. The amount of biological available nitrogen determines the amount of biomass that can be build up by living organisms. Therefore, it is crucial to know the nitrogen flux into the biosphere, to understand the balances in the carbon cycle. In this project I propose to study this new bacterial physiology in order to understand, which factors control the activity of nitrogen oxidizing bacteria. We need to know how widespread these bacteria are, to estimate their influence on the global nitrogen cycle, and I propose to investigate the interactions between nitrogen oxidizers and other relevant bacteria of the nitrogen cycle.
Summary
The largest reservoir for nitrogen on earth is the atmosphere that contains 78 percent nitrogen gas. Until now the only known biological process interacting with elemental nitrogen is the bacterial reduction of nitrogen to ammonia for the build up of biomass (nitrogen fixation). This reaction requires energy and is only carried out in the absence of other nitrogen sources, such as ammonia or nitrate. Thermodynamically, the oxidation of nitrogen to nitrate with oxygen releases reasonable amounts of energy, but no bacterium using this redox couple has been known until today. We have isolated a marine bacterium, which is capable of growing in the dark with nitrogen gas as electron donor and oxygen as electron acceptor while forming nitrate. As this microorganism can also use carbondioxide as a carbon source it basically lives of air. While oxidizing atmospheric nitrogen gas the bacterium releases large amounts of nitrate and thereby enhances the amount of fixed nitrogen available for other organisms. At the moment the apparent flux of elemental nitrogen to the ocean by bacterial nitrogen fixation is much smaller than the loss of nitrogen through bacterial denitrification, suggesting that we are missing a major input of nitrogen. This newly discovered physiology of nitrogen oxidation could close this large gap in our understanding of the nitrogen cycle. The amount of biological available nitrogen determines the amount of biomass that can be build up by living organisms. Therefore, it is crucial to know the nitrogen flux into the biosphere, to understand the balances in the carbon cycle. In this project I propose to study this new bacterial physiology in order to understand, which factors control the activity of nitrogen oxidizing bacteria. We need to know how widespread these bacteria are, to estimate their influence on the global nitrogen cycle, and I propose to investigate the interactions between nitrogen oxidizers and other relevant bacteria of the nitrogen cycle.
Max ERC Funding
1 450 673 €
Duration
Start date: 2008-07-01, End date: 2013-06-30
Project acronym LASER-ARPES
Project Laser based photoemission: revolutionizing the spectroscopy of correlated electrons
Researcher (PI) Felix Baumberger
Host Institution (HI) UNIVERSITE DE GENEVE
Call Details Starting Grant (StG), PE3, ERC-2007-StG
Summary It is proposed to develop a novel instrument for angular resolved photoelectron spectroscopy (ARPES) by combining a laser based ultraviolet light source with a state-of-the-art electron spectrometer. This combination will be unique in Europe and will push this important technique to an entirely new level of resolution, comparable to the thermal broadening at 1 K and nearly an order of magnitude lower than the resolution achievable in practical ARPES experiments with the latest synchrotron light sources. The low photon energy of this new source will also markedly enhance the bulk sensitivity of ARPES and thus enable the investigation of interesting materials that were not accessible so far. These new capabilities will be used to study the subtle quantum many-body states of correlated electrons in transition metal oxides, a frontier topic in condensed-matter physics. Specifically, we will focus on electronic instabilities in perovskites and elucidate how different degrees of freedom play together to determine the often vastly different properties of chemically closely related materials. Moreover, we will apply modern electron spectroscopy to correlated molecular solids with complex phase diagrams that challenge existing theory for satisfactory explanations. This field is largely unexplored but is fundamental for advances in molecular electronics.
Summary
It is proposed to develop a novel instrument for angular resolved photoelectron spectroscopy (ARPES) by combining a laser based ultraviolet light source with a state-of-the-art electron spectrometer. This combination will be unique in Europe and will push this important technique to an entirely new level of resolution, comparable to the thermal broadening at 1 K and nearly an order of magnitude lower than the resolution achievable in practical ARPES experiments with the latest synchrotron light sources. The low photon energy of this new source will also markedly enhance the bulk sensitivity of ARPES and thus enable the investigation of interesting materials that were not accessible so far. These new capabilities will be used to study the subtle quantum many-body states of correlated electrons in transition metal oxides, a frontier topic in condensed-matter physics. Specifically, we will focus on electronic instabilities in perovskites and elucidate how different degrees of freedom play together to determine the often vastly different properties of chemically closely related materials. Moreover, we will apply modern electron spectroscopy to correlated molecular solids with complex phase diagrams that challenge existing theory for satisfactory explanations. This field is largely unexplored but is fundamental for advances in molecular electronics.
Max ERC Funding
1 450 825 €
Duration
Start date: 2008-08-01, End date: 2013-07-31
Project acronym MASPIC
Project Spin currents in magnetic nanostructures
Researcher (PI) Mathias Kläui
Host Institution (HI) JOHANNES GUTENBERG-UNIVERSITAT MAINZ
Call Details Starting Grant (StG), PE3, ERC-2007-StG
Summary MaSpic will create an autonomous team at the University of Konstanz to investigate the interaction between magnetization, spin - polarized and pure diffusive spin currents using novel instrumentation and innovative theoretical approaches. A thorough understanding of the fundamental charge and spin transport interaction mechanisms, key to use of the spin degree of freedom for Spintronics, will be developed. To understand the interplay between spin-polarized charge currents and magnetization configurations (adiabatic vs. non-adiabatic electron transport), the reciprocal effects of magnetization on the current (magnetoresistance) and of the current on magnetization (spin transfer torque) will be correlated for the same spin structures. Non-intrusive high resolution imaging at variable temperature will be used to probe the non-adiabaticity and help understand the hotly debated influence of thermal excitations on transport. Pure diffusive spin currents will be efficiently generated and used to manipulate magnetization with ultra-low power dissipation. The poorly understood spin current generation by the Spin Hall Effect and spin current propagation will be probed by direct imaging and the sign of the spin accumulation and influence of scattering determined to separate intrinsic and extrinsic effects. For the measurements a unique variable temperature high resolution SEMPA imaging system will be acquired and further developed including ultra-fast electrical contacts. Theoretical modelling using an atomistic Heisenberg approach will go beyond the conventional micromagnetic calculations that are limited to 0K. To understand thermal transport effects, temperature dependent simulations with adiabatic and non-adiabatic spin torque terms will accompany experiments. Realistic lattice structures and heterostructures will be modelled to simulate the influence of the pure spin currents on the magnetization using spatially varying interface torque terms, not previously possible.
Summary
MaSpic will create an autonomous team at the University of Konstanz to investigate the interaction between magnetization, spin - polarized and pure diffusive spin currents using novel instrumentation and innovative theoretical approaches. A thorough understanding of the fundamental charge and spin transport interaction mechanisms, key to use of the spin degree of freedom for Spintronics, will be developed. To understand the interplay between spin-polarized charge currents and magnetization configurations (adiabatic vs. non-adiabatic electron transport), the reciprocal effects of magnetization on the current (magnetoresistance) and of the current on magnetization (spin transfer torque) will be correlated for the same spin structures. Non-intrusive high resolution imaging at variable temperature will be used to probe the non-adiabaticity and help understand the hotly debated influence of thermal excitations on transport. Pure diffusive spin currents will be efficiently generated and used to manipulate magnetization with ultra-low power dissipation. The poorly understood spin current generation by the Spin Hall Effect and spin current propagation will be probed by direct imaging and the sign of the spin accumulation and influence of scattering determined to separate intrinsic and extrinsic effects. For the measurements a unique variable temperature high resolution SEMPA imaging system will be acquired and further developed including ultra-fast electrical contacts. Theoretical modelling using an atomistic Heisenberg approach will go beyond the conventional micromagnetic calculations that are limited to 0K. To understand thermal transport effects, temperature dependent simulations with adiabatic and non-adiabatic spin torque terms will accompany experiments. Realistic lattice structures and heterostructures will be modelled to simulate the influence of the pure spin currents on the magnetization using spatially varying interface torque terms, not previously possible.
Max ERC Funding
1 610 786 €
Duration
Start date: 2008-08-01, End date: 2014-04-30
Project acronym OPTNANO
Project Quantum optics in nanostructures
Researcher (PI) Stephanie Reich
Host Institution (HI) FREIE UNIVERSITAET BERLIN
Call Details Starting Grant (StG), PE3, ERC-2007-StG
Summary Nanomaterials are intriguing structures for quantum optics. Their color depends on their size and shape; they are very selective in the wavelengths they absorb and emit. Although nanostructures have been used to color windows and surfaces since the Middle Ages, we lack the understanding how size, shape, and microscopic structure control the optical properties of nanomaterials. In this project, we plan to develop a fundamental description of quantum optics in one-dimensional nanosystems. Core concepts will be quantum confinement and electron interactions when carriers are forced into a small space. The proposed work will focus on carbon nanotubes as a model nanosystem. The tubes show pronounced confinement effects; they emit and absorb light in the near infrared and visible. We will measure optical transitions, quantum cross sections, and electron interaction using luminescence, Raman scattering, and photoconductivity. The optical properties will be tailored by selecting specific tube types and changing the tube environment. A description of optical processes is incomplete without considering defects in real nanostructures. We will develop techniques to study and introduce imperfections. Their optical signatures and their effect on light emission will be determined on individual tubes. The experiments will be complemented by materials modeling. We will describe confinement effects and Coulomb interaction in semiempirical calculations of nanotube light absorption. The knowledge gained on carbon nanotubes will be applied to predict and study the optical properties of other one-dimensional systems. The goal is to obtain a robust and transferable model of quantum optics in nanostructures. This project will also advance characterization of nanomaterials by optical spectroscopy and applications of nanotubes as light detectors and emitters. We plan to develop tools for nanotube population analysis (tube type) and to test carbon tubes as wavelength-selective photodetectors
Summary
Nanomaterials are intriguing structures for quantum optics. Their color depends on their size and shape; they are very selective in the wavelengths they absorb and emit. Although nanostructures have been used to color windows and surfaces since the Middle Ages, we lack the understanding how size, shape, and microscopic structure control the optical properties of nanomaterials. In this project, we plan to develop a fundamental description of quantum optics in one-dimensional nanosystems. Core concepts will be quantum confinement and electron interactions when carriers are forced into a small space. The proposed work will focus on carbon nanotubes as a model nanosystem. The tubes show pronounced confinement effects; they emit and absorb light in the near infrared and visible. We will measure optical transitions, quantum cross sections, and electron interaction using luminescence, Raman scattering, and photoconductivity. The optical properties will be tailored by selecting specific tube types and changing the tube environment. A description of optical processes is incomplete without considering defects in real nanostructures. We will develop techniques to study and introduce imperfections. Their optical signatures and their effect on light emission will be determined on individual tubes. The experiments will be complemented by materials modeling. We will describe confinement effects and Coulomb interaction in semiempirical calculations of nanotube light absorption. The knowledge gained on carbon nanotubes will be applied to predict and study the optical properties of other one-dimensional systems. The goal is to obtain a robust and transferable model of quantum optics in nanostructures. This project will also advance characterization of nanomaterials by optical spectroscopy and applications of nanotubes as light detectors and emitters. We plan to develop tools for nanotube population analysis (tube type) and to test carbon tubes as wavelength-selective photodetectors
Max ERC Funding
1 097 820 €
Duration
Start date: 2008-08-01, End date: 2013-07-31
Project acronym PHYTOCHANGE
Project New approaches to assess the responses of phytoplankton to Global Change
Researcher (PI) Bjoern Christian Rost
Host Institution (HI) ALFRED-WEGENER-INSTITUT HELMHOLTZ-ZENTRUM FUR POLAR- UND MEERESFORSCHUNG
Call Details Starting Grant (StG), PE8, ERC-2007-StG
Summary Phytoplankton are responsible for a major part of global primary production due to the immensity of the marine realm and are heavily implicated in global biosphere equilibriums by driving elemental chemistry in surface oceans, exporting massive amounts of C to sediments and influencing ocean-atmosphere gas exchange. Climate change will alter the marine environment within the next 100 years. Increasing atmospheric CO2 has already caused higher aquatic pCO2 levels and lower pH (ocean acidification) and rising temperature will impact ocean stratification, and hence light and nutrient conditions. Phytoplankton will be affected by these Earth system transformations in many ways, altering the complex balance of biogeochemical cycles and climate feedback mechanisms. Prediction of how phytoplankton may respond at the cellular and ecosystem levels is a key challenge in global change research. The proposed project will investigate physiological reactions of 3 important phytoplankton groups (diatoms, coccolithophores, cyanobacteria) to environmental factors which will be affected by global change (pCO2/pH, light, nutrients). Using an innovative combination of cutting-edge mass-spectrometric and fluorometric techniques, a suite of in vivo assays will be applied in lab and field experiments to develop a process-based understanding of cellular responses. Specific biogeochemical issues will be addressed since diatoms are the main drivers of vertical organic C fluxes, coccolithophores regulate ocean alkalinity through calcification, and N2-fixing cyanobacteria control availability of reactive N. These are relevant in different marine zones, from Southern Ocean to equatorial oligotrophic waters. Data will significantly improve understanding of key processes in phytoplankton and will be exploited in multidisciplinary contexts ranging from molecular to ecological processes and, through cellular and ecosystem models, to predictions of marine biosphere responses to future global change
Summary
Phytoplankton are responsible for a major part of global primary production due to the immensity of the marine realm and are heavily implicated in global biosphere equilibriums by driving elemental chemistry in surface oceans, exporting massive amounts of C to sediments and influencing ocean-atmosphere gas exchange. Climate change will alter the marine environment within the next 100 years. Increasing atmospheric CO2 has already caused higher aquatic pCO2 levels and lower pH (ocean acidification) and rising temperature will impact ocean stratification, and hence light and nutrient conditions. Phytoplankton will be affected by these Earth system transformations in many ways, altering the complex balance of biogeochemical cycles and climate feedback mechanisms. Prediction of how phytoplankton may respond at the cellular and ecosystem levels is a key challenge in global change research. The proposed project will investigate physiological reactions of 3 important phytoplankton groups (diatoms, coccolithophores, cyanobacteria) to environmental factors which will be affected by global change (pCO2/pH, light, nutrients). Using an innovative combination of cutting-edge mass-spectrometric and fluorometric techniques, a suite of in vivo assays will be applied in lab and field experiments to develop a process-based understanding of cellular responses. Specific biogeochemical issues will be addressed since diatoms are the main drivers of vertical organic C fluxes, coccolithophores regulate ocean alkalinity through calcification, and N2-fixing cyanobacteria control availability of reactive N. These are relevant in different marine zones, from Southern Ocean to equatorial oligotrophic waters. Data will significantly improve understanding of key processes in phytoplankton and will be exploited in multidisciplinary contexts ranging from molecular to ecological processes and, through cellular and ecosystem models, to predictions of marine biosphere responses to future global change
Max ERC Funding
1 399 984 €
Duration
Start date: 2008-06-01, End date: 2013-05-31
Project acronym QUASOM
Project Quantifying and modelling pathways of soil organic matter as affected by abiotic factors, microbial dynamics, and transport processes
Researcher (PI) Markus Reichstein
Host Institution (HI) MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Call Details Starting Grant (StG), PE8, ERC-2007-StG
Summary Soils play a critical role in the coupled carbon-cycle climate system. However, our scientific understanding of the role of soil biological-physicochemical interactions and of vertical transport for biogeochemical cycles is still limited. Moreover the representation of soil processes in current biosphere models operating at global scale is crude compared to vegetation processes like photosynthesis. Hence, the general aim of this project is to improve our understanding of the key interactions between the biological and the physicochemical components of the soil system that are often not explicitly considered in current experimental and modeling approaches. However, these interactions are likely to influence the biogeochemical cycles for a large part of the terrestrial biosphere and thus have the potential to significantly impact the Earth System as a whole. This will be achieved through an approach that integrates new soil mesocosm experiments, field data from ongoing European projects and soil process modeling. In mesocosm tracer experiments the fate of new and autochthonous soil organic matter will be followed under varying temperature and moisture regimes, explicitly investigating the role of microbiota. This project will test the hypothesis that transfer coefficients between soil organic matter pools, respiration and microbial biomass formation are constant as implemented in current soil organic matter models. Novel soil model structures will be developed that may explicitly account for the role of microbes and transport for soil organic matter dynamics. This will be supported by multiple-constraint model identification techniques, which allows testing and achieving model consistency with several observation types and theory. The soil modules will be incorporated into global terrestrial biosphere models which are coupled and uncoupled to the atmosphere allowing specific model experiments for investigating feedback mechanisms between soil, climate, and vegetation.
Summary
Soils play a critical role in the coupled carbon-cycle climate system. However, our scientific understanding of the role of soil biological-physicochemical interactions and of vertical transport for biogeochemical cycles is still limited. Moreover the representation of soil processes in current biosphere models operating at global scale is crude compared to vegetation processes like photosynthesis. Hence, the general aim of this project is to improve our understanding of the key interactions between the biological and the physicochemical components of the soil system that are often not explicitly considered in current experimental and modeling approaches. However, these interactions are likely to influence the biogeochemical cycles for a large part of the terrestrial biosphere and thus have the potential to significantly impact the Earth System as a whole. This will be achieved through an approach that integrates new soil mesocosm experiments, field data from ongoing European projects and soil process modeling. In mesocosm tracer experiments the fate of new and autochthonous soil organic matter will be followed under varying temperature and moisture regimes, explicitly investigating the role of microbiota. This project will test the hypothesis that transfer coefficients between soil organic matter pools, respiration and microbial biomass formation are constant as implemented in current soil organic matter models. Novel soil model structures will be developed that may explicitly account for the role of microbes and transport for soil organic matter dynamics. This will be supported by multiple-constraint model identification techniques, which allows testing and achieving model consistency with several observation types and theory. The soil modules will be incorporated into global terrestrial biosphere models which are coupled and uncoupled to the atmosphere allowing specific model experiments for investigating feedback mechanisms between soil, climate, and vegetation.
Max ERC Funding
946 800 €
Duration
Start date: 2008-09-01, End date: 2014-02-28
