Competing charge density wave orders in quasi-1D RNiC2 compounds (R = rare earth metal)

Abstract

Ternary rare-earth nickel dicarbides RNiC2 (R = rare-earth metal) crystallize in the orthorhombic CeNiC2-type crystal structure with broken inversion symmetry. Since decades, these compounds attract much attention due to the presence of large variety of ground states, such as: unconventional superconductivity, magnetism, multiple charge density wave (CDW) transitions, as well as complex interplay between CDW and rare-earth magnetism, and then finally, recently reported topological features of their quasi-1D electronic structure [1-5]. Due to the interconnected degrees of freedom (lattice, electronic, magnetic), RNiC2 family serves as a platform to study the interplay between various types of ordering. The main focus in this presentation will be put on the CDW phases which have been previously found to form in RNiC2 (R = Pr - Lu, Y) compounds with the ordering temperature scaling linearly with the unit-cell volume [2]. We will discuss the difference between two competing types of CDW order adapted in the RNiC2 family: the incommensurate q1-CDW preferred by the early-lanthanide-based RNiC2 (R = Pr - Sm) compounds and the commensurate q2-CDW state formed in the late-lanthanide-based RNiC2 (R = Ho - Lu) representatives. We will also refer to the CDWs interplay with the magnetic order as well as the topology of the electronic structure. Our discussion will be provided based on the comprehensive studies of RNiC2 single crystals grown by the floating zone method. We will present crystallographic characteristics explored via single-crystal XRD, as well as electronic, thermodynamic, and magnetic properties studied by a variety of techniques revealing anisotropic features of the selected RNiC2 single crystals [6, 7]. Our experimental results are complemented with additional insight obtained from the DFT calculations of the electronic structure.Acknowledgement: Financial support for M.R. by grant BPN/BEK/2021/1/00245/DEC/1 of The Polish National Agency for Academic Exchange (NAWA) is gratefully acknowledged. References [1] V. Babizhetskyy et al., Handbook on the Physics and Chemistry of Rare Earths, Vol. 52, North-Holland, Amsterdam, pp. 1-263. (2017) [2] M. Roman et al., Phys. Rev. B 99, 035136 (2018) [3] S. Shimomura et al., Phys. Rev. B 93, 165108 (2016) [4] K.K. Kolincio et al., Phys. Rev. Lett. 125, 176601 (2020) [5] R. Ray et al., npj Quantum Materials 7, 1 (2022) [6] M. Roman et al. Phys. Rev. B 107, 125137 (2023) [7] S. Steiner et al, Phys. Rev. B 97, 205115 (2018)