Significant enhancement of superconductivity in copper-doped 2H-TaSe2

A series of CuxTaSe2 (0 <= x <= 0.12) samples were prepared and characterized via x-ray diffraction, magnetization, resistivity, and heat capacity measurements. We found that the charge density wave phases in 2H-CuxTaSe2 are noticeably suppressed and the superconducting critical temperatures T-c are significantly enhanced from 0.14 K for pure TaSe2 to about 2 K in the Cu-doped samples. The maximum T-c of 2.7 K was obtained in the optimally doped sample with x = 0.07. The crystal structure of the Cu0.07TaSe2 was refined by the Rietveld method. Magnetic measurements revealed that Cu0.07TaSe2 is a bulk superconductor with upper critical field H-c2 (0) of 4.41 T. Analysis of specific heat data shows that the effective electron-phonon coupling and density of states at the Fermi level are enhanced in the Cu-doped samples. We present an electronic phase diagram for the 2H-CuxTaSe2 system.