Spin gap in TlRuO and the possible formation of Haldane chains in three-dimensional crystals

Lee, S.*; Park, J.-G.*; Adroja, D. T.*; Khomskii, D.*; Streltsov, S.*; McEwen, K. A.*; Sakai, Hironori   ; Yoshimura, Kazuyoshi*; Anisimov, V. I.*; Mori, Daisuke*; Kanno, Ryoji*; Ibberson, R.*

Here we show that the three-dimensional cubic system of TlRuO most probably evolves into a one-dimensional spin-one Haldane system with a spin gap below 120 K, accompanied by anomalies in the structure, resistivity, and susceptibility. We argue that these anomalies are due to an orbital ordering of Ru electrons, with a strong coupling among three degrees of freedom: orbital, spin, and lattice. Our work provides a unique example of the spontaneous formation of Haldane system with an insight into the intriguing interplay of different degrees of freedom.