Thermodynamic study of novel strongly correlated electron systems

Surface plot of the specific heat capacity divided by temperature of Ce0.5La0.5B6. The external magnetic field is applied along the [110] direction. Phase I is a paramagnetic phase, phase II is an antiferroquadrupolar phase and the nature of phase IV is still unknown (Figure taken from D. Jang et al., npj Quantum Materials 2, 62 (2017))

The Max Planck Institute for Chemical Physics of Solids (MPI CPfS) is one of the leading research facilities in both characterizing known and discovering new exotic strongly correlated electron systems. Recent work on lanthanide-based materials have resulted in major breakthroughs – the discovery of one of only two existing Ytterbium-based superconductors YbRh2Si2 [1] or the quasi-one-dimensional ferromagnetic quantum critical system YbNi4P2 [2]. When it comes to finding new compounds, significant progress has been made in the field of heavy-fermion and superconducting actinide-based systems [3-5] (see also the PhD project “Solid-state synthesis of correlated electron materials”).

Because of their typically low exchange interactions, both lanthanide- and actinide-based compounds have to be characterized and studied at very low temperatures and in high magnetic fields in order to comprehensively understand their behaviour. Essential are  precise measurements of their thermodynamic properties like specific heat or thermal expansion [6-8]. This work will be carried out at the MPI CPfS, with the help of dilution refrigerators which are able to reach temperatures as low as 20 mK and incorporate magnetic fields as high as 20 T. For even higher magnetic fields up to almost 100 T, measurements will be performed in the Dresden High Magnetic Field Laboratory.

We are looking for a motivated PhD student with background in material science and solid-state physics, who is interested in performing low-temperature and high-field thermodynamic measurements in order to elucidate unconventional behaviour of new strongly correlated electron materials.

[1] E. Schuberth, M. Tippmann, L. Steinke, S. Lausberg, A. Steppke, M. Brando, C. Krellner, C. Geibel, R. Yu, Q. Si, and F. Steglich
Emergence of superconductivity in the canonical heavy-electron metal YbRh2Si2
Science 351, 6272 (2016)
[2] A. Steppke, R. Küchler, S. Lausberg, E. Lengyel, L. Steinke, R. Borth, T. Lühmann, C. Krellner, M. Nicklas, C. Geibel, F. Steglich, M. Brando
Ferromagnetic Quantum Critical Point in the Heavy-Fermion Metal YbNi44(P1-xAsx)2
Science 339, 933 (2013)
[3] A. Amon, I. Zelenina, P. Simon, M. Bobnar, M. Naumann, E. Svanidze, F. Arnold, H. Borrmann, U. Burkhardt, W. Schnelle, E. Hassinger, A. Leithe-Jasper, and Y. Grin
Tracking aluminium impurities in single crystals of the heavy-fermion superconductor UBe13
Sci. Rep. 8, 10654 (2018)
[4] E. Svanidze, A. Amon, R. Gumeniuk, A. Leithe-Jasper
´Intermetallic Compounds with Thorium and Uranium
MPI CPfS Status Report (2018)
[5] E. Svanidze, A. Amon, R. Borth, Y. Prots, M. Schmidt, M. Nicklas, A. Leithe-Jasper, and Yu. Grin
Empirical way for finding new uranium-based heavy-fermion materials
Phys. Rev. B 99, 220403(R) (2019)
[6] H. Wilhelm, T. Lühmann, T. Rus, and F. Steglich
A compensated heat-pulse calorimeter for low temperatures
Rev. Sci. Instrum. 75, 2700 (2004)
[7] M. Brando
Development of a relaxation calorimeter for temperatures between 0.05 and 4 K
Rev. Sci. Instr. 80, 095112 (2009)
[8] R. Küchler, T. Bauer, M. Brando, and F. Steglich
A compact and miniaturized high resolution capacitance dilatometer for measuring thermal expansion and magnetostriction
Rev. Sci. Instr. 83, 095102 (2012)

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