Fe-doping–induced superconductivity in the charge-density-wave system 1T-TaS ₂

Abstract

We report the interplay between charge-density-wave (CDW) and superconductivity of 1T -FexTa1−xS2 (0 x 0.05) single crystals. The CDW order is gradually suppressed by Fe-doping, accompanied by the disappearance of pseudogap/Mott-gap as shown by the density functional theory (DFT) calculations. The superconducting state develops at low temperatures within the CDW state for the samples with the moderate doping levels. The superconductivity strongly depends on x within a narrow range, and the maximum superconducting transition temperature is 2.8 K as x = 0.02. For high doping level (x > 0.04), the Anderson localization (AL) state appears, resulting in a large increase of resistivity. We present a complete electronic phase diagram of the 1T -FexTa1−xS2 system that shows a dome-like Tc(x).

Coexistence of superconductivity and charge-density-wave domain in 1T-FexTa1−xSSe

“…As x ≥ 0.06, the resistivity rapidly increases with decreasing temperature in the low temperature range, which is possibly ascribed to the disorder-induced Anderson localization (AL), [28] as suggested previously in Fe-doped 1T -TaS 2 . [18,29] In Fig. 2(b), an obvious resistivity drop was observed in 1T -TaSSe at T N CCDW = 392 K. As reported in 1T -TaS 2−x Se x (0 ≤ x ≤ 2), [20] the 392 K NCCDW in 1T -TaSSe is enhanced from the 355 K NCCDW in 1T -TaS 2 .…”

“…[11,12,13,14] With increasing temperature, it melts into a nearly-commensurate CDW (NCCDW), which forms roughly hexagonal CDW domains. [15] The electronic phase diagrams in pressurized 1T -TaS 2 , [16,17] 1T -Fe x Ta 1−x S 2 (0 ≤ x ≤ 0.05), [18,19] or 1T -TaS 2−x Se x (0 ≤ x ≤ 2), [20,21] uniformly show the SC coexists with the NC-CDW phase. In 1T -TaS 2 , the Mott CCDW order almost completely gaps the Fermi-surface (FS) due to strong electron-electron interaction so that it probably leaves no states for the superconducting condensate.…”

“…As it melts into the NCCDW phase with the formation of CDW domains, the SC resides in. [18,20] Therefore, we further selected 1T -TaSSe as the parent material, with T onset c = 3.8 K and T N CCDW = 392 K, to establish the relationship of SC and CDW domain. Besides the hydrostatic pressure method, the element doping can be effective to influence the CDW superstructure and the SC state.…”

Manipulating charge density waves in1T−TaS2by charge-carrier doping: A first-principles investigation

“…The CCDW domains shrink upon heating and finally disappear at 355 K, while the system transforms to ICCDW state. The standard metallic 1T structure appears above 535 K. Moreover, when CCDW state is suppressed, superconductivity emerges in this system [18][19][20]. One can expect that the controllable switching between those states will be helpful for figuring out the mechanism of CDW and superconductivity, and realizing the high performance memory and transistor in future technology.…”

“Checkerboard Stripe” Electronic State on Cleaved Surface of NdO0.7F0.3BiS2 Probed by Scanning Tunneling Microscopy

“…An example of these phenomena is chargedensity-wave (CDW) formation in the transition metal dichalcogenides 1-7 and trichalcogenides 8,9 , in which the superconductivity (SC) often coexists with the CDW 1-7 . Because of the coexistence of CDW and SC, these materials are important for understanding the interplay between these phenomena 4,5,7 . Another example is the high-temperature superconductivity in copper oxides 10 and iron-pnictides 11 .…”