The Subchalcogenides Ir2In8Q (Q = S, Se, Te): Dirac Semimetal Candidates with Re-entrant Structural Modulation

• DOI: 10.1021/jacs.0c00809
• Publication Date: 2020-03-11T22:15:41Z
• Authors: Jason F. Khoury; Alexander J. E. R...; Iñigo Robredo; Matthew J. Krogstad; Christos D. Malli...; Aitor Bergara; Maia G. Vergniory; Raymond Osborn; Stephan Rosenkranz; Duck Young Chung; Mercouri G. Kanat...
• Keywords: Modulation (music)

Subchalcogenides are uncommon compounds where the metal atoms in unusually low formal oxidation states. They bridge gap between intermetallics and semiconductors can have unexpected structures properties because of exotic nature their chemical bonding as they contain both metal–metal metal–main group (e.g., halide, chalcogenide) interactions. Finding new members this class materials presents synthetic challenges attempts to make them often result phase separation into binary compounds. We overcome difficulty by utilizing indium a flux synthesize large (millimeter scale) single crystals novel subchalcogenide materials. Herein, we report two Ir2In8Q (Q = Se, Te) compare structural electrical previously reported Ir2In8S analogue. Ir2In8Se Ir2In8Te crystallize P42/mnm space isostructural Ir2In8S, but also commensurately modulated (with q vectors 1/6a* + 1/6b* 1/10a* 1/10b* for Ir2In8Te, respectively) low-temperature transitions, chalcogenide anions channels experience distortion form In–Q bond alternation along ab plane. Both display re-entrant behavior, supercells appear on cooling revert original subcell below 100 K, suggesting competing electronic interactions dictate overall structure. Notably, these topological semimetal candidates with symmetry-protected Dirac crossings near Fermi level exhibit high electron mobilities (∼1500 cm2 V–1 s–1 at 1.8 K) moderate carrier concentrations (∼1020 cm–3) from charge transport measurements. This work highlights route quality intermetallic subchalcogenides behavior.