Identification of a possible superconducting transition above room temperature in natural graphite crystals
Identification of a possible superconducting transition above room temperature in natural graphite crystals
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DOI：
10.1088/1367-2630/18/11/113041
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发表时间：
2016-11-23
影响因子：
3.3
通讯作者：
Beth, Henning
中科院分区：
文献类型：
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作者：
Precker, Christian E.;Esquinazi, Pablo D.;Beth, Henning
高精度测量来自巴西矿山的高度有序的天然石墨样品的电阻，我们已经确定了一个类似于350的转变。K与at相似于40。K转变宽度。阶梯状的温度变化的电阻，其磁场的不可逆性和时间依赖性后，场的变化，符合捕获的磁通量和磁通蠕变，和部分磁通量驱逐磁化测量得到的，建议存在的颗粒超导低于350。K.零场原始状态只能在零场冷却样品之后再次达到。奇怪的是，我们在这个和其他几个石墨样品中发现的异常高的转变温度是这种转变至今未被检测到的原因。X射线衍射测量结果表明，在所有样品中均存在有序的菱面体石墨相，这表明其与Bernal相的界面可能是高温超导的起源，正如理论研究所预测的那样。在这些二维界面的颗粒超导性的本地化，防止观察到零电阻状态或一个完整的迈斯纳状态。
Measuring with high precision the electrical resistance of highly ordered natural graphite samples from a Brazil mine, we have identified a transition at similar to 350. K with at at similar to 40. K transition width. The step like change in temperature of the resistance, its magnetic irreversibility and time dependence after a field change, consistent with trapped flux and flux creep, and the partial magnetic flux expulsion obtained by magnetization measurements, suggest the existence of granular superconductivity below 350. K. The zero-field virgin state can only be reached again after zero field cooling the sample from above the transition. Paradoxically, the extraordinarily high transition temperature we found for this and several other graphite samples is the reason why this transition remained undetected so far. The existence of well ordered rhombohedral graphite phase in all measured samples has been proved by x-rays diffraction measurements, suggesting its interfaces with the Bernal phase as a possible origin for the high-temperature superconductivity, as theoretical studies predicted. The localization of the granular superconductivity at these two dimensional interfaces prevents the observation of a zero resistance state or of a full Meissner state.