A Comparative Study of 3d-Intercalated Transition Metal Dichalcogenides by Their Transport, Magnetic, and Electronic Properties
Date of Award
Doctor of Philosophy
Norman Mannella, David Mandrus
Cristian Daniel Batista, Haidong Zhou
ntercalation of transition metal dichalcogendies (TMDCs) by 3d-transition metals has been studied systematically. We mainly focus on intercalation into two host TMDCs 2H-NbS2 and 2H-TaS2 which are layered materials where the metal ions are in trigonal prismatic environment of chalcogens, the layers are separated by weak van der Waals force. So, foreign atoms or molecules can be inserted in between the layers of the TMDCs. Theun-intercalated NbS2 shows superconductivity below 6 K whereas TaS2 exhibits coexistence of the superconductivity (Tc=0.8 K) with charge density wave phase (TCDW=75 K). In this research, the NbS2 is intercalated by V atom with formula unit V0.3NbS2, while TaS2byCr with formula unit Cr1/3TaS2. Upon the intercalation, the electronic as well as magnetic structure of host materials are likely to be modified. It is believed that the charge transfer between the 3d-intercalant and host TMDC, specifically the d-band of Nb or Ta, just causes an increase in chemical potential without altering the band structure and shape and size of Fermi surface, also known as rigid band model. And, the local moment in magnetic ion gives rise to magnetism via RKKY interaction. In order to examine the effect of intercalation in V0.3NbS2 and Cr1/3TaS2, we investigated the magnetic, transport, and electronic properties. In V0.3NbS2, which crystallizes in P-31m space group, we observed canted antiferromag-netic (weak ferromagnetic) magnetic ordering with majority of charge carriers as hole type. From ARPES measurements, additional bands are appeared to cross the Fermi level and shape and size of the Fermi surface are modified as compared to NbS2. Also, V-3d states are present near the Fermi level. These findings demonstrate that the simple rigid band picture is not viable in V0.3NbS2 compound. Moreover, from the photon dependent ARPES measurements strong kz dispersion is found in contrast to that of host NbS2. Similarly, intercalated Cr1/3TaS2 crystallizes in P6322 space group orders ferromagnetically. Surface structure is investigated by STM, LEED, and core level photoemmission experiments. The resonant photoemmission and ARPES measurements are performed to examine the effect of charge transfer between Cr and TaS2 layer.
Sapkota, Deepak, "A Comparative Study of 3d-Intercalated Transition Metal Dichalcogenides by Their Transport, Magnetic, and Electronic Properties. " PhD diss., University of Tennessee, 2019.