Superconductivity in pressurized Rb_0.8Fe_2−ySe_2−xTe_x

Abstract

We report the finding of pressure-induced elimination and reemergence of superconductivity in Rb 0.8 Fe 2−y Se 2−x Te x (x = 0, 0.19 and 0.28) superconductors that belong to the family of A-245 superconductors (A = K, Rb, TlRb and Cs), characterized by the presence of an antiferromagnetic (AFM) long-ranged order phase with the superlattice structure of Fe-cavacies. In this study, we investigate the connections between superlattice, AFM phase and superconductivity via the combined approaches of Te doping and application of external pressure. Our data reveal that the superconductivity of the ambient-pressure superconducting phase (SC-I) and the AFM long-ranged order as well as the superconductivity of the pressure-induced phase (SC-II) in the host samples can be synchronously tuned by Te doping. At x = 0.4, the SC-I and AFM long-range ordered phases as well as the SC-II phase disappear together, indicating that the two superconducting phases have intrinsic connections with the AFM phase. Furthermore, in-situ synchrotron x-ray diffraction measurements indicate that the superlattice structure in the x = 0.4 sample still exists at ambient pressure, but collapses at the same pressure where the superlattice of the superconducting samples is destructed. These results provide new insight into understanding the physics of this type of superconductors.

Pressure dependence of superconductivity in low- and high- Tc phases of (NH3)yNaxTerao1, Yang2, Xing3 et al. 2018Phys. Rev. B104180View full textAdd to dashboardCite

“…The pressure dependence of superconductivity in various metal-intercalated two-dimensional (2D) layered materials has been extensively studied in past decades [1][2][3][4][5][6][7][8][9][10]. The exciting behavior of a superconducting transition temperature T c that varies with pressure (p) was observed in superconducting K 0.8 Fe 1.7 Se 2 , K 0.8 Fe 1.78 Se 2 and Tl 0.6 Rb 0.4 Fe 1.67 Se 2 crystals, which showed a double-dome superconductivity with pressure [1].…”

Superconducting properties of (NH3)yLixFeSe0.5Te0.5 under pressure

“…Above T c , the R/R(280 K) value for the low-T c phase at 0.49 GPa increases with increasing temperature up to ∼200 K, and it saturates above 200 K, while the R/R(280 K) value for the high-T c phase at 1.00 GPa increases with increasing temperature up to ∼200 K, where it decreases slightly. Such a convex R-T plot is often observed for metal-doped FeSe [4,8]. Namely, the R/R(280 K)-T plots show metallic-like behavior with weak carrier localization.…”

“…Furthermore, it should be noted that the T c -p phase diagram was reported for Rb 0.8 Fe 2−δ Se 2−z′ Te z′ (z′=0.19 and 0.28) by Gu et al [8], indicating that the maximum T c values of SC-I and SC-II decrease with an increase in z′ (i.e. the amount of Te); the sample was prepared by the annealing method, and NH 3 was not included (i.e.…”

“…Actually, the c range of 13.5-16.5 Å is an undecided area, in that the correlation of T c and c is still unclear. Therefore, the behavior of T c (8) against c at 13.5-16.5 Å must be pursued in (NH 3 ) y M x FeSe 0.5 Te 0.5 , which may lead to the hidden relationship between T c and c (or the plain spacing of FeSe 0.5 Te 0.5 ).…”

“…Recently, the pressure dependence of superconductivity in metal-doped two-dimensional (2D) layered materials has attracted much attention [1][2][3][4][5][6][7][8][9][10][11] because of the expectation that a new superconducting pairing mechanism will be developed, as well as the emergence of new superconducting phases exhibiting higher superconducting transition temperatures (T c 's) than those observed at ambient pressure. The pressure-driven high-T c phase has been extensively investigated in metal-doped FeSe [6][7][8][9][10][11]. The first discovery of a pressuredriven high-T c phase was reported for K 0.8 Fe 1.7 Se 2 , K 0.8 Fe 1.78 Se 2 and Tl 0.6 Rb 0.4 Fe 1.67 Se 2 crystals [6], and our group reported a very high value of T c (= 49 K) in (NH 3 ) y Cs x FeSe at 21 GPa [9], showing that the double-dome T c -p phase diagram consisted of two superconducting phases (SC-I and SC-II).…”