The unusual suppression of superconducting transition temperature in double-doping 2H-NbSe₂

Abstract

2H-NbSe 2 is one of the most widely researched transition metal dichalcogenide (TMD) superconductors, which undergoes charge-density wave (CDW) transition at T CDW about 33 K and superconducting transition at T c of 7.3 K. To explore the relation between its superconductivity and Fermi surface nesting, we combined S substitution with Cu intercalation in 2H-NbSe 2 to make Cu x NbSe 2-y S y (0 ≤ x = y ≤ 0.1).Upon systematic substitution of S and intercalation of Cu ions into 2H-NbSe 2 , we found that when the Cu and S contents (x = y  0.06) increases, the T c decreases in Cu x NbSe 2-y S y . While at higher x and y values, T c keeps a constant value near 2 K, which is not commonly observed for a layered TMD. For comparison, we found the simultaneous substitution of Nb by Cu and Se by S in Cu x Nb 1-x Se 2-y S y (0 ≤ x = y ≤ 0.06) lowered the T c substantially faster. We construct a superconducting phase diagrams for our double-doping compounds in contrast with the related single-ions doping systems.

Superconductivity in CuIr 2–x Al x Te4 telluride chalcogenides

“…Low-dimensional layered transition metal dichalcogenides (TMDs) are other opportune material platforms for the exploration of various quantum instabilities, [12][13][14][15][16][17][18][19][20][21] especially the interplay between SC and CDW, in which the CDW order refers to condensate with periodic modulations of the crystalline lattice and conduction electron density in real space. Typically, the SC can be induced and a dome-shape superconducting phase diagram is formed upon suppressing the CDW order, [22][23][24][25][26][27] which is highly similar to the phase diagrams of unconventional high-T c cuprates and iron-based supercon-ductors.…”

Robust Superconductivity in (ZnxCu1–x)0.5IrTe2

“…In particular, the study on the interaction between the CDW and SC in the low-dimensional transition-metal chalcogenides (TMDs) becomes a hotspot topic. Former research results suggest that most of the interaction between SC and CDW in the TMDs is competitive, while SC and CDW can coexist in some cases (e.g., 2H-TaSe 2 , 2H-NbSe 2 ). − Nevertheless, SC/CDW is usually vulnerable to chemical doping. − 1T-Cu x TiSe 2 is a typical example, where the CDW order can be destroyed and followed by the appearance of SC with the highest T c of 4.2 K, where the intercalation of Cu dedicates the electrons to the 1T-TiSe 2 host. Analogously, other dopants (e.g., Ta, Pd) being electron suppliers also can ruin the CDW order and result in the emergence of SC in the chemical doping 1T-TiSe 2 systems. − …”

NbSeTe—a new layered transition metal dichalcogenide superconductor

“…Up until now, numerous theoretical and experimental works about its physical properties have been reported. The researchers prefer to use the effective and mature methods to regulate and control the CDW and the superconducting behavior, such as chemical doping [12][13][14][15][16][17][18] , adopting high pressure [19][20][21][22] , gating 23 and controlling layers of the nanoscale samples. It has been established previously that the intercalation of 3d transition metals (such as Zn, Al, Co, Ni, Fe) into 2H-NbSe2 quickly destroyed the Tc to < 1 K. [24][25] Recently, Cava group has also reported that the intercalation of Cu into 2H-NbSe2 to obtain CuxNbSe2 (0 ≤ x ≤ 0.09) 4 15 .…”

“…The similar behavior is observed in our recently reported double doping CuxNbSe2-ySy (0 ≤ x = y ≤ 0.09) system. 16 It has also been found that its superconductivity is suppressed by the substitution on Se site by Te atoms into 2H-NbSe2 to form 2H-NbTexSe2-x (x = 0, 0.10, 0.20), where 2H polytype was maintained. 26 These previously reported works all maintained 2H-NbSe2 structure no matter intercalation or substitution.…”