Pressure-Induced Superconductivity in Iron-Based Spin-Ladder Compound BaFe2+δ(S1−xSex)3

Abstract

The iron-based superconductors had a significant impact on condensed matter physics. They have a common structural motif of a two-dimensional square iron lattice and exhibit fruitful physical properties as a strongly correlated electron system. During the extensive investigations, quasi-one-dimensional iron-based spin-ladder compounds attracted much attention as a platform for studying the interplay between magnetic and orbital ordering. In these compounds, BaFe2S3 and BaFe2Se3 were found to exhibit superconductivity under high pressure, having a different crystal and magnetic structure at low temperature. We report a brief review of the iron-based spin-ladder compound and recent studies for BaFe2+δ(S1−xSex)3. BaFe2(S0.75 Se0.25)3 is in the vicinity of the boundary of two different magnetic phases and it is intriguing to perform high pressure experiments for studying superconductivity, since effects of large magnetic fluctuations on superconductivity are expected. The effect of iron stoichiometry on the interplay between magnetism and superconductivity is also studied by changing the iron concentration in BaFe2+δSe3.

Pressure-induced electronic phase transition and superconductivity in spin-ladder compounds BaFe2(S1−x Se x )3

“…For sample x = 0.37, R 2.5 K goes down again for P > 20.5 GPa. In fact, similar phenomenon was also observed in the previous pressure studies on BaFe 2 (S 1−x Se x ) 3 , but was ignored [6,19,27]. According to this change of the resistance behavior, we suggest that an electronic phase transition takes place around the pressure of 18 GPa.…”

“…For sample x = 0.07, a down-turn behavior, as indicated by the red arrow, is observed on the temperature-dependent resistance curve for P ∼ 8.6 GPa. The temperature of this downturn behavior is around 11 K. Similar behavior has also been reported for BaFe 2 Se 3 and BaFe 2 (S 0.75 Se 0.25 ) 3 in the similar pressure range, which has been ascribed to the onset of superconductivity [6]. For samples x = 0.18 and x = 0.37, pressure over 20 GPa has been achieved, but no superconductivity is observed.…”

“…To date, high pressure study on BaFe 2 (S 1−x Se x ) 3 is still relatively lacking. Previously, pressure studies on samples near the critical doping level (x ∼ 0.23) have revealed clearly different results [6,19]. Investigation of the pressure effects for samples with more doping levels should be helpful to make clear of the superconductivity nature in the present system.…”

“…In the counterpart BaFe 2 Se 3 , a resistivity drop around 11 K is observed for 11 GPa < P < 15 GPa, which has been ascribed to the onset of superconductivity [4]. Since no zeroresistance is noticed in pressurized BaFe 2 Se 3 , the superconductivity nature is debatable [4][5][6]. The crystal structures of BaFe 2 S 3 and BaFe 2 Se 3 are featured by the Q1D Fe 2 X 3 (X = S and Se) ladder formed by edge-shared FeX 4 tetrahedra [1,4].…”

“…It is suggested that the observation of superconductivity is strongly dependent on the T N value, which may be influenced by the starting Fe content during the synthesis of the crystals [1,18]. A slight excess Fe in the starting materials is supposed to optimize the T N value and thus benefits the occurrence of superconductivity [1,6,18]. The hydrostatic pressure environment was also thought to play an important role in the observation of bulk superconductivity.…”