News from the Physics of Correlated Department

Teaser 1542015325

Revealing the topological nature of the surface states in SmB6

9. November 2018
The topological nature of the surface states in SmB6 is exposed by means of scanning tunneling spectroscopy on samples with magnetic substituents or by using magnetic tunneling tips. These local measurements are complemented by global transport measurements on identical samples. [mehr]
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A universal strategy to design superior water splitting electrocatalysts with in situ fast surface reconstruction

5. Oktober 2018
A universal strategy based on electrochemically induced fast reconstruction of amorphous nanofilm precursors is proposed for exploring ultrahigh mass activity and extremely stable bifunctional water splitting catalysts. The facile reconstruction strategy is promising for the development of novel efficient catalysts for other advanced energy conversion and storage devices. [mehr]
Teaser 1534757857

From single-ion Kondo effect to Kondo lattice formation

20. August 2018
Scanning tunneling spectroscopy data on the archetypical heavy fermion metal YbRh2Si2 establish a hierarchy of energy scales, with the dominance of the lattice Kondo effect requiring temperatures well (about an order of magnitude) below the single-ion Kondo temperature of about 25 K. Only if the lattice Kondo correlations are sufficiently established, quantum critical fluctuations can evolve. [mehr]
Teaser 1530010457

Visualizing polaron formation in EuB6

26. Juni 2018
A combination of scanning tunneling microscopy and locally resolved magnetic stray field measurements unambiguously revealed the polaron formation in the ferromagnetic semimetal EuB6. These polarons are at the heart of the colossal magnetoresistive effects near the ferromagnetic transition in this material. [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]
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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]
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