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TT: Fachverband Tiefe Temperaturen

TT 34: Correlated Electrons: f-Electron Systems and Heavy Fermions 1

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 T_c = 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.