Physical properties studies of the multiple CDW phase transitions in quasi-1D RNiC₂ compounds (R = rare earth metal)

Abstract

Ternary rare-earth nickel dicarbides RNiC2 crystallize in the orthorhombic 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 waves (CDWs), as well as complex interplay between CDW and rare-earth magnetism, and then finally, recently reported topological features of their quasi-1D electronic structure. In this presentation we will discuss multiple CDW phase transitions observed in RNiC2 (R = Pr - Lu, Y) compounds with the ordering temperature scaling linearly with the unit-cell volume. We will focus on 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) and the commensurate q2-CDW state formed in the late lanthanide-based RNiC2 (R = Ho - Lu). We will also refer to the CDWs interplay with the magnetic order as well as topology of the electronic structure. We will present crystallographic characteristics explored via single-crystal XRD, as well as electronic, thermoelectric, thermodynamic and magnetic properties studied by a variety of techniques revealing anisotropic features of selected RNiC2 single crystals. 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.