Dresden 2020 – wissenschaftliches Programm
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TT 34.4: Vortrag
Mittwoch, 18. März 2020, 10:15–10:30, HSZ 204
Superconductivity and heavy-fermion behavior in locally non-centrosymmetric LnIr2As2 (Ln = La and Ce) — •Seunghyun Khim, Markus König, and Christoph Geibel — Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany
Compounds containing atoms with a large atomic number are considered a candidate for the realization of unconventional phenomena induced by spin-orbit splitting of degenerated bands and orbitals. In combination with a non-centrosymmetric crystal structure, the resulting asymmetric spin-orbit coupling (ASOC) gives rise to spin-momentum coupled electronic structures. Appearance of superconductivity or strong electronic correlations within these electronic structures could lead to nontrivial phases. Accordingly, LnIr2As2 (Ln = La and Ce) in the CaBe2Ge2-type structure are promising systems because of the presence of the 5d-orbital element as well as of the lack of local inversion symmetry on each sublayer in the unit cell. Here, we present studies on single crystals of LaIr2As2 and CeIr2As2. We discover superconductivity in LaIr2As2 with a transition temperature Tc = 1.5 K. The Sommerfeld coefficient is γ0 ∼ 9 mJ/mol-K2, implying weak electronic correlations. CeIr2As2, on the other hand, shows enhanced effective mass due to the Kondo interactions between the Ce3+ magnetic moments and itinerant electrons. Below 5 K, the specific-heat C/T increases with decreasing T to reach ∼ 350 mJ/mol-K2 at 0.5 K, revealing non-Fermi liquid character. We discuss the physical properties of these compounds in detail, in view of the possible ASOC.