We investigate the high-pressure phase of the iron-based superconductor FeSe_0.89S_0.11 using transport and tunnel diode oscillator studies using diamond anvil cells. We construct detailed pressure-temperature phase diagrams that indicate that the superconducting critical temperature is strongly enhanced by more than a factor of four towards 40 K above 4 GPa. The resistivity data reveal signatures of a fan-like structure of non-Fermi liquid behaviour which could indicate the existence of a putative quantum critical point buried underneath the superconducting dome around 4.3 GPa. With further increasing the pressure, the zero-field electrical resistivity develops a non-metallic temperature dependence and the superconducting transition broadens significantly. Eventually, the system fails to reach a fully zero-resistance state, and the finite resistance at low temperatures becomes strongly current-dependent. Our results suggest that the high-pressure, high-T_c phase of iron chalcogenides is very fragile and sensitive to uniaxial effects of the pressure medium, cell design and sample thickness. This high-pressure region could be understood assuming a real-space phase separation caused by nearly concomitant electronic and structural instabilities.

我们利用金刚石砧池进行传输和隧道二极管振荡器研究，研究了铁基超导体 FeSe _0.89 S _0.11的高压相。我们构建了详细的压力-温度相图，表明超导临界温度在 4 GPa 以上时强烈提高了四倍以上，达到 40 K。电阻率数据揭示了非费米液体行为的扇状结构的特征，这可能表明埋藏在 4.3 GPa 左右的超导穹顶下方的假定量子临界点的存在。随着压力的进一步增加，零场电阻率呈现出非金属温度依赖性，超导转变显着展宽。最终，系统无法达到完全零电阻状态，并且低温下的有限电阻变得强烈依赖于电流。我们的结果表明，铁硫族化物的高压、高温_c相非常脆弱，并且对压力介质、单元设计和样品厚度的单轴效应敏感。假设由几乎同时存在的电子和结构不稳定性引起的实空间相分离，可以理解该高压区域。