Mechanism of the Anomalous Superconductivity in Black Phosphorus

在P-T相图中，沿沿着五条不同的路径测量了黑磷的压力诱导超导电性。压力对超导转变温度（Tc）的影响强烈地依赖于相图中的路径。在很高的压力下，黑磷沿着路径（D）的Tc高达10.7 K，转变开始温度超过13 K。当以赤磷为起始原料，沿路径（D）在4.2 K沿着加压时，Tc随压力的增加而急剧增加，在30 GPa时，Tc上升到13 K，转变起始温度达到18 K。在液氮温度下，利用同步辐射X射线研究了压力诱导相变。在77 K时相变压力高于室温。在77 K时，两相或三相在6-14 GPa的宽压力范围内共存。这些结果表明，在液氦温度下，简单立方相必然存在非均匀态，这种非均匀性与反常超导电性密切相关。

The pressure-induced superconductivity in black phosphorus was measured along five different paths in a P-T phase diagram. The effect of pressure on the superconductivity transition temperature(Tc) strongly depends on the path in the phase diagram. The Tc of black phosphorus along the path(D) went up to 10.7 K and onset temperature of transition was beyond 13 K at very high pressures. When the red phosphorus as a starting material was pressurized at 4.2 K along the path(D), the Tc steeply increased with increasing pressure; it raised up to 13 K and onset temperature of transition reached 18 K at 30 GPa. This is the highest temperature in elements.Pressure-induced phase transitions have also studied by X-ray study with synchrotron radiation at liquid nitrogen temperature. The pressure of the transition at 77 K was higher than that at room temperature. Two or three phases coexisted in wide pressure range 6-14 GPa at 77 K. These results suggest that there must be inhomogeneous state in simple cubic phase at liquid helium temperature and the inhomogeneity is closely related to the anomalous superconductivity.