Physics

 

Dr. Sitaram Ramakrishnan
University of Bayreuth, Germany

R2Ir3Si5 (R = Lu, Er, Ho) at room temperature crystallizes in the orthorhombic Ibam, U2Co3Si5 structure type [1]. Depending on R the compound undergoes a first-order charge density wave transition (CDW) at 200 K for Lu, below 150 K for Er and below 70 K for Ho based on single crystal X-ray diffraction (SXRD). The resistivity (ρ) and magnetic susceptibility (χ) measurements were performed for the compounds Lu2Ir3Si5 and Er2Ir3Si5 agrees with SXRD [2, 3, 4, 5]. Initially Lu2Ir3Si5 was investigated through Xray powder diffraction, stating the symmetry is lowered from orthorhombic Ibam to monoclinic P21/m at 87 K [2]. Lu2Ir3Si5 was also studied through TEM experiments where the wave vector of the CDW phase transition at 95 K was reported to be q = δ(¯121), δ = 0.23 ∼ 0.25 [6]. We have studied both Er2Ir3Si5 and Lu2Ir3Si5 via SXRD down to 20 K where we found the structure is actually is triclinic I¯1 despite the strong monoclinic distortion of the lattice accompanied by similar wavevectors reported for Lu2Ir3Si5 by Lee et.al [6], and that the Ir-Ir band is responsible for the CDW [4, 5]. Here we report the incommensurately modulated crystal structures in relation to the physical properties for all three compounds as a whole detailing the similarities and differences in the CDW between them.