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Description
R$_2$Ir$_3$Si$_5$ (R = Ho, Er, Lu) crystallize in the U$_2$Co$_3$Si$_5$ structure type at room temperature (orthorhombic space group Ibam) [1]. Upon cooling they undergo first-order charge-density-wave (CDW) phase transitions, as evidenced by anomalies with hysteresis in the temperature dependencies of the electrical resistivity ($\rho$), specific heat ($C_p$), magnetic susceptibility ($\chi$), Seebeck coefficient ($S$) and thermal conductivity ($\kappa$) [1-4]. The CDW character of the low-temperature phases is corroborated by the appearance of satellite reflections at q = (0.2495, 0.4973, 0.2483) in diffraction experiments [4,5]. Single-crystal x-ray diffraction has revealed that the incommensurate CDW is accompanied by a strong monoclinic lattice distortion, while the symmetry of the CDW phase is reduced to triclinic. Here, we discuss the microscopic mechanism of CDW formation on the basis of a superspace analysis of single-crystal x-ray diffraction data [4].
Acknowledgement: Single-crystal X-ray diffraction data were collected at Beamline P24 of PETRA-III at DESY, Hamburg, Germany.
References
[1] Y. Singh, D. Pal, S. Ramakrishnan, A. M. Awasthi and S. K. Malik, Phys. Rev. B 71, 045109 (2005).
[2] Y. K. Kuo, K. M. Sivakumar, T. H. Su and C. S. Lue, Phys. Rev. B 74, 045115 (2006).
[3] N. S. Sangeetha, A. Thamizhavel, C. V. Tomy, S. Basu, A. M. Awasthi, P. Rajak, S. Bhattacharyya, S. Ramakrishnan and D. Pal, Phys. Rev. B 91, 205131 (2015).
[4] S. Ramakrishnan, A. Schonleber, T. Rekis, N. van Well, L. Noohinejad, S. van Smaalen, M. Tolkiehn, C. Paulmann, B. Bag, A. Thamizhavel, D. Pal and S. Ramakrishnan, Phys. Rev. B 101, 060101(R) (2020).
[5] M. H. Lee, C. H. Chen, M. -W. Chu, C. S. Lue and Y. K. Kuo, Phys. Rev. B 83, 155121 (2011).