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Rosner, Helge
Helge Rosner

Telefon: +49 351 4646-2233
Fax: +49 351 4646-4902
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Teaser 1523277942

Ein duktiler anorganischer Halbleiter bei Raumtemperatur

9. April 2018
Duktilität ist eine charakteristische Eigenschaft von Metallen und metallischen Materialien, wird aber selten bei Halbleitern und Isolatoren beobachtet. Wissenschaftler des MPI CPfS und des Shanghai Institute of Ceramics der Chinesischen Akademie der Wissenschaften berichten hohe metallartige Duktilität des Halbleiters a-Ag2S. Ein einheitliches Bild wurde durch Kombination verschiedener Präparations- und Charakterisierungs-Techniken mit quantenchemischer Analyse der chemischen Bindung erhalten. [mehr]
Teaser 1522938715

c-axis dimer and its electronic breakup: The insulator-to-metal transition in Ti2O3

5. April 2018
New X-ray spectra of the electronic structure of the transition metal oxide Ti2O3 reveal unprecedented electronic molecular detail about the transition from insulator to metal as temperature increases. [mehr]
Teaser 1522939065

Satya Narayan Guin receives a Humboldt Research Fellowship for Postdoctoral Researchers

3. April 2018
The Alexander von Humboldt foundation, Germany, awarded Satya a Humboldt Research Fellowship for postdoctoral researchers. He is currently working as a postdoc with Prof. Claudia Felser. [mehr]
Teaser 1525783686

Leopoldina: Claudia Felser

23. März 2018
Zu Beginn dieses Jahres wurde Claudia Felser in die Leopoldina aufgenommen. [mehr]
Teaser 1520425779

GDCh: Claudia Felser

16. Februar 2018
In der Gesellschaft Deutscher Chemiker gibt es strukturelle Neuerungen: Seit Beginn des Jahres steht der Forschungsgruppe Festkörperchemie und Materialforschung Professor Felser vor. [mehr]
Teaser 1516367701

Charge Order and Electron Localization in a Molecule-Based Solid 

20. Januar 2018
Charge ordering in cationic mixed-valence compounds is of crucial importance for materials science. The prototypic example for a transition from a charge-disordered  to a charge-ordered state has been magnetite, Fe3O4, where Evert Verwey  observed a sudden jump in resistivity near -150°C. In the journal Science Advances now a research team of scientists from Germany and Slovenia reports a Verwey-type charge-ordering transition in a different class of mixed-valence compounds which is composed of negatively charged dioxygen molecules. [mehr]
Teaser 1516357120

Be21Pt5: eine supraleitende komplexe intermetallische Elektronenmangelverbindung

19. Januar 2018
The crystal structure and chemical bonding scenario of the complex intermetallic compound Be21Pt5 was solved in a joint collaboration spearheaded by scientists from the Max-Planck Institute for Chemical Physics of Solids. Be21Pt5 shows the rare case of superconductivity in a complex intermetallic compound with over 400 atoms per unit cell. Real space analysis of the calculated electron density and the electron localizability indicator (ELI) reveal structural units with collective intra-cluster interactions, termed cluster bonding, which are linked in the structure by strongly polar three-center interactions. [mehr]
Teaser 1515485098

Ground state wave function of the strongly correlated topological insulator SmB6

8. Januar 2018
SmB6 is under focus because it may be the first topological insulator that is also strongly correlated. It is intermediate valent and a gap opens only at low temperatures due to an intricate interplay between correlation effects and hybridization, yet the surface is always conducting. The topological properties of the surface are determined by the bulk so that it is surprising that the bulk crystal-field ground state of Sm3+ was unknown until now despite many attempts by e.g. neutron scattering. Recently, scientists from the Max-Planck Institute for Chemical Physics of Solids and the University of Cologne clarified this issue by applying a new technique, namely core-level non-resonant inelastic x-ray scattering, see Sundermann et al., Phys. Rev. Letter 120, 016402 (2018). The finding that the ground state is the Γ8 quartet and not the Γ7 doublet, contradicts all existing band structure calculations and illustrates in a sobering manner the difficulties in making reliable predictions for the properties of correlated systems. [mehr]
Teaser 1515484115

LaNiO3: a highly metallic strongly correlated oxide with antiferromagnetic correlations

8. Januar 2018
The rare earth nickelates RNiO3 with the high Ni3+ oxidation state have continued to attract enormous interest due to the famous metal-insulator transition and unusual charge and spin-order phenomena together with the prediction for multi-ferroicity and even superconductivity in thin film hetero-structures. One of the long standing puzzles is why LaNiO3 seems to be the only RNiO3 that stays metallic and paramagnetic down to lowest temperatures. Recently, the team around Alexander Komarek was able to grow centimeter-sized and impurity-free single crystals of LaNiO3 and then to unveil its true electrical and magnetic properties. The result is that the phase diagram of the RNiO3 system has to be redrawn and that theoretical concepts have to be reconsidered about how to explain the properties and the electronic structure of these high oxidation state materials. [mehr]
Teaser 1512391613

Pressure-induced Ferromagnetism in FeTe

4. Dezember 2017
The high-temperature superconductivity in iron-pnictides and –chalcogenides is based on the intricate interplay of crystal structure, electronic and magnetic states. The concerted study by scientists from different departments of the Max Planck Institute for Chemical Physics of Solids and from the Leibniz Institute for Solid State and Materials Research found for iron-telluride the remarkable result that hydrostatic pressure leads to the emergence of ferromagnetic order in a peculiar way. [mehr]
Teaser 1511777964

Ultraclean metal-like conductivity in semimetallic WP2

27. November 2017
Ultraclean metals show high conductivity with a high number of charge carriers, whereas semiconductors and semimetals with low charge carriers normally show a low conductivity. This scenario in semimetals can be changed if one can protect the carriers from scattering.  [mehr]
Teaser 1511528185

The Iron Age: about the understanding of the new iron-based high-temperature superconductors and related compounds

24. November 2017
In the new iron-based superconductors (FeSC), superconductivity occurs close to an antiferromagnetic phase. This indicates that correlation effects may be important in these materials. Theoretical calculations predict that different from cuprates, besides the on-site Coulomb interaction also the on-site Hund exchange interaction plays an important role in the correlation effects of FeSCs. This would mean that a completely new state of correlated matter has appeared which has been termed “Hund’s metal”. [mehr]
Teaser 1510315415

Thermodynamic signatures of field-induced phase transitions in graphite

10. November 2017
Graphite is a model system for the study of electrons in the so-called magnetic quantum limit. This quantum limit is attained when the magnetic field is strong enough to confine the charge carriers to their lowest Landau levels. It is expected that the model of the free electron gas fails beyond this limit since here electron interactions may play a significant role in determining the electronic ground state. Indeed, our thermodynamic studies in high magnetic field revealed that even electron-lattice interaction has to be taken into account in addition to electron-electron interaction.    [mehr]
Teaser 1510308460

New features in multipolar heavy-fermion materials

10. November 2017
The simple cubic structure of CeB6 does not change while intricate multipolar phenomena are developed upon a non-magnetic La substitution. However, phase diagrams of Ce1-xLaxB6 have been elusive for the last decades. Recently, detailed phase transitions in Ce1-xLaxB6 have been revealed by scientists of MPI-CPfS, TU-Dresden, and I. M. Frantsevich Institute. In addition, a simple feature which is likely to be observed in a multipolar heavy-fermion system has been found.  [mehr]
Teaser 1509706697

Robust Bain distortion in the premartensite phase of a platinum-substituted Ni2MnGa magnetic shape memory alloy

23. Oktober 2017
The premartensite phase of shape memory and magnetic shape memory alloys is believed to be a precursor state of the martensite phase with preserved austenite phase symmetry. The thermodynamic stability of the premartensite phase and its relation to the martensitic phase is still an unresolved issue, even though it is critical to the understanding of the functional properties of magnetic shape memory alloys. [mehr]
Teaser 1508741737

Dr. Steffen Wirth zum Fellow der American Physical Society (APS) gewählt

20. Oktober 2017
Steffen Wirth erhält die Fellowship für „seine grundlegenden Beiträge zu unserem Verständnis von stark korrelierten Elektronensystemen, insbesondere bei reduzierten Längenskalen, einschließlich des Kondo-Effekts und magnetischer Wechselwirkungen", wie es in der Ernennungsurkunde heißt.  [mehr]
Teaser 1506601098

Elektronen mit maximaler Spinaufspaltung

28. September 2017
Die Oberflächen von Materialien können einzigartige elektronische Eigenschaften aufweisen, weil sich die Elektronen dort manchmal sehr verschieden vom Inneren der Verbindungen verhalten. Insbesondere die intrinsisch gebrochenen Symmetrien an der Oberfläche im Vergleich zum Inneren der Probe erlauben eine Unterscheidung von Energiezuständen nach ihrem Spin. Dieser Effekt könnte in neuartigen elektronischen Geräten verwendet werden, die sowohl mit der Ladung als auch mit dem Spin von Elektronen arbeiten. [mehr]
Teaser 1505894760

Quantum Tricritical Points

20. September 2017
The concept of 'quantum critical point', the zero temperature point of a line of 2nd order phase transitions, is rather modern: It is nowadays strongly investigated mainly in connection with unconventional superconductivity. Recent experimental and theoretical works have shown that some metals show competing ferro- and antiferromagnetic order at very low temperature. This allows for the possibility of multiple critical points and thus, at T=0, for quantum tricritical points. [mehr]
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