Investigation of the Charge Density Wave Ordering in Intercalated ZrTe2 materials

Abstract

Superconductivity (SC) and charge-density-wave (CDW) ordering are correlated electronic phases whose coexistence in certain materials has been a subject of significant interest. In general, the suppression of CDW–either through chemical doping or external pressure–can lead to the emergence of SC at low temperatures. The interplay between these phenomena has been debated for decades and is considered highly material-dependent. Transition-metal dichalcogenides (TMDCs), MX2 (where M is a transition metal and X is a chalcogen), often exhibit CDW ordering or are proximate to CDW phases. However, the question of whether SC can be induced in these materials by suppressing CDW ordering has not been thoroughly explored. In this work, we investigate ZrTe2, a member of the TMDC family. While pristine ZrTe2 does not exhibit CDW ordering, Ni-intercalated ZrTe2 has been reported to show CDW ordering at 287 K alongside superconductivity at 4.1 K. To further understand the competing phases in this system, we conducted a systematic study of the transport properties of Cr𝑥ZrTe2 (i.e., Cr-intercalated ZrTe2. Additionally, Ni0.04ZrTe2 was analyzed to gain insights into the nature of CDW ordering and the structural changes induced by Ni intercalation. This study employs a home-built resistivity measurement setup capable of scanning temperatures from 4.3 K to 295 K using the temperature gradient of a helium-storage dewar. The thesis is divided into two parts: the first focuses on the design and validation of the low-temperature resistivity setup, while the second investigates intercalated ZrTe2 systems. We synthesized Cr𝑥ZrTe2 (for 𝑥 = 0.25–0.45), optimizing crystal growth conditions for each composition, and characterized them by measuring their temperature-dependent electrical resistivity (in some cases in-field measurements using a commercial transport measurement system is also carried out). These results provide a foundation for future anisotropic studies of Cr𝑥ZrTe2 to further unravel the complex magnetic interactions and competing electronic phases in these systems.