High-pressure phase diagrams of FeSe1−xTex: correlation between suppressed nematicity and enhanced superconductivity

Abstract

The interplay among magnetism, electronic nematicity, and superconductivity is the key issue in strongly correlated materials including iron-based, cuprate, and heavy-fermion superconductors. Magnetic fluctuations have been widely discussed as a pairing mechanism of unconventional superconductivity, but recent theory predicts that quantum fluctuations of nematic order may also promote high-temperature superconductivity. This has been studied in FeSe1−xSx superconductors exhibiting nonmagnetic nematic and pressure-induced antiferromagnetic orders, but its abrupt suppression of superconductivity at the nematic end point leaves the nematic-fluctuation driven superconductivity unconfirmed. Here we report on systematic studies of high-pressure phase diagrams up to 8 GPa in high-quality single crystals of FeSe1−xTex. When Te composition x(Te) becomes larger than 0.1, the high-pressure magnetic order disappears, whereas the pressure-induced superconducting dome near the nematic end point is continuously found up to x(Te) ≈ 0.5. In contrast to FeSe1−xSx, enhanced superconductivity in FeSe1−xTex does not correlate with magnetism but with the suppression of nematicity, highlighting the paramount role of nonmagnetic nematic fluctuations for high-temperature superconductivity in this system.

Chemical pressure effect of the electron-doped FeSe films with an electric double-layer-transistor structure

“…The Te-and S-content dependence of T c in undoped [32,33] and e-doped FeSe 1−x A x (A=Te, S) films on LAO. Those of undoped FeSe 1−x Te x films on CaF 2 [31,42] and those of bulk undoped [50][51][52] and intercalated samples [24,27,28] are also plotted. The dotted lines are guides for the eye.…”

Induced Superconducting Transition in Ultra-Thin Iron-Selenide Films by a Mg-Coating Process

“…Among the family of electrical materials, high-temperature superconducting material always attracts considerable attention not only considering its huge potential in high-efficiency electric transport and high-field magnets, but also due to the probable complement in condensed matter physics [1]. Iron-based superconductors [2][3][4][5] are considered one of the promising candidates that might unveil the mechanism of high-temperature superconductivity (HTS) since dramatic enhancement in critical temperature (T c ) has been repeatedly achieved in binary iron selenide (FeSe) composite through a variety of strategies, including elemental substitution [6][7][8]/intercalation [9,10], pressurization [11,12], liquidgate [13], and the substrate-induced heavy electron doping into FeSe unit cells [14][15][16]. Apparently, the HTS achieved in FeSe system reflects the exotic and unique properties in the unconventional Fe-based superconductors and is worth further investigation.…”

Fragile pressure-induced magnetism in FeSe superconductors with a thickness reduction

“…Intriguingly, high-T c phases appear at both ends of the SDW dome, suggesting that the enhanced magnetic fluctuations may help to increase T c [46]. A recent result on FeSe 1−x Te x shows that, as Te content increases, the nematic phase can also be suppressed, while the pressure-induced SDW phase disappears gradually against x [55]. At x > 0.10, no magnetic order is observed under pressure [55].…”

“…A recent result on FeSe 1−x Te x shows that, as Te content increases, the nematic phase can also be suppressed, while the pressure-induced SDW phase disappears gradually against x [55]. At x > 0.10, no magnetic order is observed under pressure [55]. However, a superconducting dome still forms near the nematic phase, indicating that at least for the FeSe 1−x Te x series, the nematic fluctuations alone may also help to promote T c [55].…”

“…At x > 0.10, no magnetic order is observed under pressure [55]. However, a superconducting dome still forms near the nematic phase, indicating that at least for the FeSe 1−x Te x series, the nematic fluctuations alone may also help to promote T c [55].…”