Structural, magnetic, and electrical characterizations reveal that SnP with an unusual valence state (nominally ${\mathrm{Sn}}^{3+}$) undergoes a ferroelectriclike structural transition from a simple NaCl-type structure to a polar tetragonal structure at approximately 250 K at ambient pressure. First-principles calculations indicate that the experimentally observed tetragonal distortion enhances the charge transfer from Sn to P, thereby making the polar tetragonal phase energetically more stable than the nonpolar cubic phase. Hydrostatic pressure is found to promptly suppress the structural phase transition in SnP, leading to the emergence of bulk superconductivity in a phase-competitive manner. These findings suggest that control of ferroelectriclike instability in a metal can be a promising way for creating novel superconductors.

中文翻译：

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具有异常价态的SnP的极性-非极性相界处的超导

结构，磁性和电学特征表明SnP具有异常的价态（名义上 ${锡}^{3+}$）在环境压力下约250 K处经历了从简单的NaCl型结构到极性四方结构的铁电结构转变。第一性原理计算表明，实验观察到的四方畸变增强了从Sn到P的电荷转移，从而使极性四方相在能量上比非极性立方相更加稳定。发现静水压力可迅速抑制SnP中的结构相变，从而以相竞争的方式出现体超导性。这些发现表明，控制金属中类似铁电体的不稳定性可能是产生新型超导体的有前途的方法。