Project acronym Com4Com
Project Collective modes in 4d-metal compounds and heterostructures
Researcher (PI) Bernhard Keimer
Host Institution (HI) MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Call Details Advanced Grant (AdG), PE3, ERC-2014-ADG
Summary Compounds of transition metals with 4d valence electrons (“4d metals”) play eminent roles in many areas of condensed matter physics ranging from unconventional superconductivity to oxide electronics, but fundamental questions about the interplay between the spin-orbit coupling and electronic correlations at the atomic scale remain unanswered. Momentum-resolved spectroscopies of collective electronic excitations yield detailed insight into the magnitude and spatial range of the electronic correlations, and have thus decisively shaped the conceptual understanding of quantum many-body phenomena in 3d-electron systems. We will devise and build a novel resonant inelastic x-ray scattering (RIXS) instrument capable of determining the dispersion relations of electronic collective modes in 4d-metal compounds with full momentum-space coverage, high energy resolution, and monolayer sensitivity.
Data from this instrument will yield comprehensive information about the interaction parameters specifying the electronic Hamiltonians of 4d-electron materials, unique insight into the spin-orbital composition of their excited-state wavefunctions, and definitive tests of proposals to realize Kitaev models with spin-liquid states that are potentially relevant in topological quantum computation. The element-specificity of RIXS will also allow us to determine the microscopic exchange interactions in complex materials with both 3d and 4d valence electrons, and its high sensitivity will enable experiments on operational device structures comprising only a few monolayers. We will thus be able to tightly integrate momentum-resolved spectroscopy with state-of-the-art, monolayer-by-monolayer deposition methods of 4d metal-oxide films and heterostructures. The results will fuel a feedback loop comprising synthesis, characterization, and modeling, which will greatly advance our ability to design materials and devices whose functionality derives from the collective organization of electrons.
Summary
Compounds of transition metals with 4d valence electrons (“4d metals”) play eminent roles in many areas of condensed matter physics ranging from unconventional superconductivity to oxide electronics, but fundamental questions about the interplay between the spin-orbit coupling and electronic correlations at the atomic scale remain unanswered. Momentum-resolved spectroscopies of collective electronic excitations yield detailed insight into the magnitude and spatial range of the electronic correlations, and have thus decisively shaped the conceptual understanding of quantum many-body phenomena in 3d-electron systems. We will devise and build a novel resonant inelastic x-ray scattering (RIXS) instrument capable of determining the dispersion relations of electronic collective modes in 4d-metal compounds with full momentum-space coverage, high energy resolution, and monolayer sensitivity.
Data from this instrument will yield comprehensive information about the interaction parameters specifying the electronic Hamiltonians of 4d-electron materials, unique insight into the spin-orbital composition of their excited-state wavefunctions, and definitive tests of proposals to realize Kitaev models with spin-liquid states that are potentially relevant in topological quantum computation. The element-specificity of RIXS will also allow us to determine the microscopic exchange interactions in complex materials with both 3d and 4d valence electrons, and its high sensitivity will enable experiments on operational device structures comprising only a few monolayers. We will thus be able to tightly integrate momentum-resolved spectroscopy with state-of-the-art, monolayer-by-monolayer deposition methods of 4d metal-oxide films and heterostructures. The results will fuel a feedback loop comprising synthesis, characterization, and modeling, which will greatly advance our ability to design materials and devices whose functionality derives from the collective organization of electrons.
Max ERC Funding
3 176 850 €
Duration
Start date: 2016-01-01, End date: 2020-12-31
Project acronym PICOPROP
Project Photo Induced Collective Properties of Hybrid Halide Perovskites
Researcher (PI) Laszlo Forro
Host Institution (HI) ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE
Call Details Advanced Grant (AdG), PE3, ERC-2014-ADG
Summary The recent discovery of the organo-inorganic perovskite CH3NH3PbI3 as very efficient material in photoelectric conversion is multifaceted: it turns out that this compound is promising not only in photovoltaics, but it is lasing, it gives bright light emitting diodes, promising in water splitting and we are persuaded that it can play an important role in basic sciences, as well.
We have recently realized that under white light illumination the photoelectrons, due to their very long recombination time, stay in the conduction band and the resistivity of a single crystal shows a metallic behavior. If the lifetime is sufficiently long and the density of these excited carrier is high enough they could condense into a Fermi sea. The project’s goal is to realize this highly unusual state and to document its properties by magneto-transport and spectroscopic techniques. We will check in our model compound the long-sought superconductivity of photo-excited carriers, extensively searched for in cuprates, if we could stabilize it by fine tuning the interactions by hydrostatic pressure under constant illumination.
The availability of high quality samples is primordial for this program. It turns out that CH3NH3PbI3 is ideal compound, it seems to be almost free of charged defects (its room temperature resistance is 5 orders of magnitude higher than that of Phosphorus doped Silicon at 1013 cm-3 doping concentration) and we can grow excellent single crystals of it. Furthermore, it has a flexibility in material design: one can vary all the constituents, and even the dimensionality by making layered materials with the main chemical motifs. A special effort will be devoted to tune the spin-orbit coupling by different elements, since this could be at the origin of the long recombination time of the photo-electrons.
We suspect that the highly tunable, clean and disorder-free doping obtained by shining light on these ionic crystals opens a new era in material discovery.
Summary
The recent discovery of the organo-inorganic perovskite CH3NH3PbI3 as very efficient material in photoelectric conversion is multifaceted: it turns out that this compound is promising not only in photovoltaics, but it is lasing, it gives bright light emitting diodes, promising in water splitting and we are persuaded that it can play an important role in basic sciences, as well.
We have recently realized that under white light illumination the photoelectrons, due to their very long recombination time, stay in the conduction band and the resistivity of a single crystal shows a metallic behavior. If the lifetime is sufficiently long and the density of these excited carrier is high enough they could condense into a Fermi sea. The project’s goal is to realize this highly unusual state and to document its properties by magneto-transport and spectroscopic techniques. We will check in our model compound the long-sought superconductivity of photo-excited carriers, extensively searched for in cuprates, if we could stabilize it by fine tuning the interactions by hydrostatic pressure under constant illumination.
The availability of high quality samples is primordial for this program. It turns out that CH3NH3PbI3 is ideal compound, it seems to be almost free of charged defects (its room temperature resistance is 5 orders of magnitude higher than that of Phosphorus doped Silicon at 1013 cm-3 doping concentration) and we can grow excellent single crystals of it. Furthermore, it has a flexibility in material design: one can vary all the constituents, and even the dimensionality by making layered materials with the main chemical motifs. A special effort will be devoted to tune the spin-orbit coupling by different elements, since this could be at the origin of the long recombination time of the photo-electrons.
We suspect that the highly tunable, clean and disorder-free doping obtained by shining light on these ionic crystals opens a new era in material discovery.
Max ERC Funding
2 495 712 €
Duration
Start date: 2015-09-01, End date: 2020-08-31
Project acronym POLTDES
Project Interacting polaritons in two-dimensional electron systems
Researcher (PI) Atac Imamoglu
Host Institution (HI) EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZUERICH
Call Details Advanced Grant (AdG), PE3, ERC-2014-ADG
Summary Reversible coupling of excitons and photons in a microcavity leads to the formation of mixed light-matter quasiparticles, called cavity-polaritons. Weakly interacting polaritons constitute a rich system for studying nonequilibrium condensation and superfluidity. While exciton-polaritons have been studied mostly in intrinsic semiconductors with no free electrons, two-dimensional modulation-doped semiconductors with strong interactions between electrons have played a central role in unravelling many-body physics using transport. In this project, we combine these two fields of research and explore the complex interplay between cavity-polaritons and strongly correlated states of two dimensional electrons embedded inside microcavities. Our principal objective is the realization of polariton mediated superconductivity of electrons in gallium arsenide. Besides demonstrating a new mechanism for Cooper-pair formation, such an observation could revolutionize the search for systems that exhibit topological order. In a reciprocal approach, we will exploit the many-body nature of optical excitations in a two-dimensional electron gas to enhance polariton-polariton interactions. This will allow us to reach the polariton blockade regime, paving the way for realization of nonequilibrium strongly interacting polaritons. In parallel, we will explore cavity-magneto-polariton excitations out of fractional quantum Hall ground states: the objective in this part is to use the strong filling factor dependence of polariton splitting to realize nonlinear optical devices which derive their photon-photon interaction from light-absorption induced transition between compressible and incompressible ground states. Concurrently, we will study charged-exciton-polaritons in monolayer transition metal dichalcogenides positioned inside a microcavity, where a large polariton Berry-curvature allows for the observation of valley Hall effect and could be used to realize topological polaritons.
Summary
Reversible coupling of excitons and photons in a microcavity leads to the formation of mixed light-matter quasiparticles, called cavity-polaritons. Weakly interacting polaritons constitute a rich system for studying nonequilibrium condensation and superfluidity. While exciton-polaritons have been studied mostly in intrinsic semiconductors with no free electrons, two-dimensional modulation-doped semiconductors with strong interactions between electrons have played a central role in unravelling many-body physics using transport. In this project, we combine these two fields of research and explore the complex interplay between cavity-polaritons and strongly correlated states of two dimensional electrons embedded inside microcavities. Our principal objective is the realization of polariton mediated superconductivity of electrons in gallium arsenide. Besides demonstrating a new mechanism for Cooper-pair formation, such an observation could revolutionize the search for systems that exhibit topological order. In a reciprocal approach, we will exploit the many-body nature of optical excitations in a two-dimensional electron gas to enhance polariton-polariton interactions. This will allow us to reach the polariton blockade regime, paving the way for realization of nonequilibrium strongly interacting polaritons. In parallel, we will explore cavity-magneto-polariton excitations out of fractional quantum Hall ground states: the objective in this part is to use the strong filling factor dependence of polariton splitting to realize nonlinear optical devices which derive their photon-photon interaction from light-absorption induced transition between compressible and incompressible ground states. Concurrently, we will study charged-exciton-polaritons in monolayer transition metal dichalcogenides positioned inside a microcavity, where a large polariton Berry-curvature allows for the observation of valley Hall effect and could be used to realize topological polaritons.
Max ERC Funding
2 482 250 €
Duration
Start date: 2015-11-01, End date: 2020-10-31
Project acronym SORBET
Project Spin Orbitronics for Electronic Technologies
Researcher (PI) Stuart Parkin
Host Institution (HI) MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Call Details Advanced Grant (AdG), PE3, ERC-2014-ADG
Summary Spintronics is a vibrant field of research that involves the intimate interaction of magnetic structure on the atomic scale with spin currents and spin-polarized charge currents. SORBET is focussed on an emerging sub-field of spintronics, namely that of spin orbitronics. Recent discoveries in this field concern the interplay of several distinct spin orbit coupling derived phenomena that, together, allow for the highly efficient current
induced motion of domain walls (DWs) in magnetic nanowires. It is proposed to explore two classes of domain-wall device concepts: a novel two terminal single-domain wall device composed of a spin-valve based structure that is deposited on a vertical wall or other 3D structure; and a 3D racetrack memory that involves multiple domain walls. The main objectives of the project involve the exploration of atomically engineered thin film magnetic nano-structures that could enable these revolutionary devices, and to unravel and exploit the new physics of this emerging field of research. To achieve these objectives fundamental breakthroughs are needed both in the thin film materials themselves and in the physics that determines the material properties and controls the motion of the DWs. These devices are innately three-dimensional and thus can overcome challenges that limit the scaling of existing two-dimensional electronic technologies.
Novel methods to fabricate these devices will be explored, especially, the use of atomic layer deposition and 3D printing techniques. An important objective will be to understand the origin of the spin orbit torques that
drive domain walls in nanowires and the detailed relationship of these torques to the DW structure; it is anticipated that this will enable even more complex 3D spin textures to be realized that have, for example, much lower threshold currents for motion than is currently possible, and that exhibit topological transport phenomena that could even be used to generate or detect domain walls.
Summary
Spintronics is a vibrant field of research that involves the intimate interaction of magnetic structure on the atomic scale with spin currents and spin-polarized charge currents. SORBET is focussed on an emerging sub-field of spintronics, namely that of spin orbitronics. Recent discoveries in this field concern the interplay of several distinct spin orbit coupling derived phenomena that, together, allow for the highly efficient current
induced motion of domain walls (DWs) in magnetic nanowires. It is proposed to explore two classes of domain-wall device concepts: a novel two terminal single-domain wall device composed of a spin-valve based structure that is deposited on a vertical wall or other 3D structure; and a 3D racetrack memory that involves multiple domain walls. The main objectives of the project involve the exploration of atomically engineered thin film magnetic nano-structures that could enable these revolutionary devices, and to unravel and exploit the new physics of this emerging field of research. To achieve these objectives fundamental breakthroughs are needed both in the thin film materials themselves and in the physics that determines the material properties and controls the motion of the DWs. These devices are innately three-dimensional and thus can overcome challenges that limit the scaling of existing two-dimensional electronic technologies.
Novel methods to fabricate these devices will be explored, especially, the use of atomic layer deposition and 3D printing techniques. An important objective will be to understand the origin of the spin orbit torques that
drive domain walls in nanowires and the detailed relationship of these torques to the DW structure; it is anticipated that this will enable even more complex 3D spin textures to be realized that have, for example, much lower threshold currents for motion than is currently possible, and that exhibit topological transport phenomena that could even be used to generate or detect domain walls.
Max ERC Funding
2 750 000 €
Duration
Start date: 2015-11-01, End date: 2020-10-31
