2016/03/18 by Bhoi, D., Khim, S., Nam, W. +6 · 1 citation
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Superconductivity (cond-mat.supr-con)
paper · doi:10.48550/arxiv.1603.05769
2H-TaSe2 has been one of unique transition metal dichalcogenides exhibiting several phase transitions due to a delicate balance among competing electronic ground states. An unusual metallic state at high-T is sequentially followed by an incommensurate charge density wave (ICDW) state at ≈ 122 K and a commensurate charge density wave (CCDW) state at ≈ 90 K, and superconductivity at T_\rmC∼0.14 K. Upon systematic intercalation of Pd ions into TaSe2, we find that CCDW order is destabilized more rapidly than ICDW to indicate a hidden quantum phase transition point at x∼0.09-0.10. Moreover, T_\rmC shows a dramatic enhancement up to 3.3 K at x = 0.08, ∼24 times of T_\rmC in 2H-TaSe2, in proportional to the density of states N(EF). Investigations of upper critical fields Hc2 in single crystals reveal evidences of multiband superconductivity as temperature-dependent anisotropy factor γH = Hc2ab/Hc2c, quasi-linear increase of Hc2c(T), and an upward, positive-curvature in Hc2ab(T) near T_\rmC. Furthermore, analysis of temperature-dependent electronic specific heat corroborates the presence of multiple superconducting gaps. Based on above findings and electronic phase diagram vs x, we propose that the increase of N(EF) and effective electron-phonon coupling in the vicinity of CDW quantum phase transition should be a key to the large enhancement of T_\rmC in PdxTaSe2.