Physical properties of semimetallic magnets UOX (X = S, Se, Te)

Opletal, P.  ; 酒井 宏典   ; 芳賀 芳範   ; 常盤 欣文  ; 山本 悦嗣  ; 神戸 振作  ; 徳永 陽  

Opletal, P.; Sakai, Hironori; Haga, Yoshinori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo

Magnetic semimetals are currently focus of research due to possible electronic topological features. Topological features originate from nontrivial band characters. One of the most interesting state is Weyl fermion which originate from band splitting driven by spin-orbit interaction due to the inversion symmetry breaking or time-reversal symmetry breaking. The materials with these properties are called Weyl semimetals. Wey fermions are expected to be robust and have high mobility, which is important for practical application of topological matter. Uranium materials are candidates for Weyl semimetals due to their strong spin-orbit interaction causing band inversion and/or strong electronic correlations, often observed as 5f magnetism. One of the possible candidates are UOX (X = S, Se, Te) compounds. UOX (X = S, Se, Te) crystallizes in tetragonal PbFCl-type structure (P4/nmm space group). Only polycrystalline samples are reported in literature. UOS, UOSe and UOTe were reported to be antiferromagnets with T = 55, 100 and 160 K, respectively. Magnetic structure of UOS and UOSe were reported to have moment along the c-axis with Q = (0,0,1/2). UOS and UOSe were both reported to exhibit semiconducting behavior on polycrystalline samples. UOTe was theoretically predicted to have nontrivial topology. Recently we have prepared first single crystals of UOX (X = S, Se, Te) and shown they exhibit semimetallic conductivity in contrast to published literature. We will present the method of preparation of single crystals, results of magnetic, transport and thermal measurements and discuss these results in connection to Weyl semimetals and results published in literature.