Strongly correlated electron systems

HZB studies of superconductors and related transition metal oxides have produced important results in the past years. The study of charge order in La1.8xEu0.2SrxCuO4 (J Fink el al., Phys. Rev. B 83, 092503 (2011)) revealed a first example of  static charge order independent of a structural phase transition and in the absence of long-range magnetic order. While charge order is not very well developed in this material, resonant soft x-ray diffraction provided the required sensitivity to observe the subtle ordering phenomenon. Similar is true for the recent observation of doping dependent charge order correlations in electron-doped cuprates proving the concept that superconductivity competes with other orders not only in almost all known classes of hole-doped cuprate superconductors. The main goal in this field is to achieve a final general understanding of the interplay of charge ordering and high-Tc superconductivity with a present focus on manipulating charge order in thin film heterostructures and by external stimulus.

HZB studies on 5f-electron based magnetism focused on the determination of magnetic-field driven phase transitions in uranium compounds such as U(Ru0.92Rh0.08)2Si2 and U2Pd2In, mainly using neutron scattering in extremeley high magnetic fields at the unique High-Field-Magnet at BER II.

In the following we present a few examples of research carried out in the field of strongly correlated electron systems within the last few years.

For a full list of publications of our institute click here.


GraphikProkes

Above the phase transition at 25.8 Tesla U2Pd2In  exhibis a complex magnetic ordering pattern © HZB


Reciprocal space mapping of three YBCO films grown on STO (001)


URuSi high field

Starting at a magnetic field strength of 23 Tesla, additional spots appear on the neutron detector that reveal the new magnetic order in the crystal. © HZB


Bluschke

Angular dependence within the a-b plane of the macroscopic saturation magnetization in bulk DyScO3. © APS


NCCO

Phase diagram of the electron-doped cuprate superconductor compound Nd2-xCexCuO4 as a function of doping and temperature. The blue and red data points indicate the boundaries for the occurrence of charge order. © APS


Scanning electron microscopy in combination with EELS electron spectroscopy permits to visualise atomic positions of the individual atoms in the heterostructure: Superconducting regions of YBaCuO are identified by yttrium (blue) and copper (pink), the ferromagnetic layers by manganese (green) and lanthanum (red). Courtesy MPI Stuttgart.