注氧类金刚石和非晶碳膜及高取向热解石墨中的类超导和磁转变
Superconducting-like and magnetic transitions in oxygen-implanted diamond-like and amorphous carbon films, and in highly oriented pyrolytic graphite
摘要：
在我们以前发表的工作中，我们已经报道了巨大的磁电阻，Andreev振荡，铁磁性和颗粒超导性在氧注入碳纤维，石墨箔，和高度定向热解石墨。在后续的研究中，将对这些注氧石墨样品进行更多的研究。我们展示了氧注入类金刚石碳薄膜，无定形碳膜，和高度取向的热解石墨的传输测量结果。值得注意的是，一个三个数量级的下降，在50 K的温度下，我们以前报道的过渡到超导状态的氧注入类金刚石碳膜的电阻观察。在50 K以下，薄膜电阻在高阻态和低阻态之间振荡，当样品处于横向磁场下时，振荡较小。绝缘态和类超导态之间的亚稳态可能反映了超导序参量（也称为纵向希格斯模）的振幅演化。对于非晶碳膜，也观察到向低阻态和亚稳态的转变。最后，高度取向的热解石墨样品电阻具有热激活项，该热激活项可以基于应用于窄SC通道的LAMH模型来理解，在窄SC通道中，热波动可以引起相位滑移。我们还发现，在氧注入碳材料中，电子电荷和自旋相关不竞争，它们的相互作用，而促进了高温超导性的出现，因此，观察到额外的意想不到的效果，如海森堡自旋波和磁结构转变。
英文摘要：
In our previously published work, we have reported colossal magnetoresistance, Andreev oscillations, ferromagnetism, and granular superconductivity in oxygen-implanted carbon fibers, graphite foils, and highly oriented pyrolytic graphite. In this follow-up research, more results on these oxygen-implanted graphite samples are presented. We show results from transport measurements on oxygen-implanted diamond-like carbon thin coatings, amorphous carbon films, and highly oriented pyrolytic graphite. Significantly, a three-order magnitude drop in the electrical resistance of the oxygen-implanted diamond-like carbon films is observed at the 50 K temperature that we have previously reported for the transition to the superconducting state. Below 50 K, the films resistance oscillates between the high and low resistance states, less when the sample is under a transverse magnetic field. This metastability between the insulating and superconducting-like states possibly reflects the evolution of the amplitude for the superconducting order parameter also known as the longitudinal Higgs mode. Transitions to low resistance state and metastability are also observed for amorphous carbon films. Finally, the highly oriented pyrolytic graphite samples resistance have a thermally activated term that can be understood on the basis of the LAMH model applied to narrow SC channels in which thermal fluctuations can cause phase slips. We also find that in oxygen-implanted carbon materials, the electron charge and spin correlations do not compete and their interplay rather facilitates the emergence of high-temperature superconductivity, and thus, additional unexpected effects like Heisenberg spin waves and magneto-structural transitions are observed.
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