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Disorder and magnetic field induced Bose-metal state in two-dimensionalTax(SiO2)1−xgranular films
Physical Review B ( IF 3.7 ) Pub Date : 2020-12-02 , DOI: 10.1103/physrevb.102.224502
Zhi-Hao He , Hua-Yao Tu , Kuang-Hong Gao , Guo-Lin Yu , Zhi-Qing Li

The origin of the intermediate anomalous metallic state in two-dimensional superconductor materials remains enigmatic. In the present paper, we observe such a state in a series of 9.0-nm-thick Tax(SiO2)1x (x being the volume fraction of Ta) nanogranular films. At zero field, the x 0.75 films undergo a Berezinskii-Kosterlitz-Thouless transition as transform from normal to superconducing states upon cooling. For the x 0.71 films, the resistance increases with decreasing temperature from 2 K down to 40 mK. A normal state to anomalous metallic state transition is observed in the x0.73 film, i.e., near the transition temperature, the resistance of the film decreases sharply upon cooling as if the system would cross over to superconducting state, but then saturates to a value far less than that in normal state. When a small magnetic field perpendicular to the film plane is applied, the anomalous metallic state occurs in the x0.75 films. It is found that both disorder and magnetic field can induce the transition from superconductor to anomalous metal and their influences on the transition are similar. For the magnetic field induced case, we find the sheet resistance R(T,H) (T and H being the temperature and the magnitude of the magnetic field, respectively) data near the crossover from the anomalous metal to superconductor and in the vicinity of the anomalous metal to insulator transition, respectively, obey unique scaling laws deduced from the Bose-metal model. Our results strongly suggest that the anomalous metallic state in the Tax(SiO2)1x granular films is bosonic and dynamical gauge field fluctuation resulting from superconducting quantum fluctuations plays a key role in its formation.

中文翻译:

二维Tax(SiO2)1-x颗粒薄膜中的无序和磁场诱导的玻色金属态

二维超导材料中的中间异常金属态的起源仍然是个谜。在本文中,我们在一系列9.0-nm厚 X二氧化硅21个-XX是Ta)纳米颗粒薄膜的体积分数。在零场,X0.75薄膜在冷却时经历了从正常状态到超导状态的转变,发生了Berezinskii-Kosterlitz-Thouless转变。为了X0.71薄膜时,电阻会随着温度从2 K降低到40 mK而增加。观察到从正常状态到异常金属状态的转变X0.73薄膜,即在转变温度附近,薄膜的电阻在冷却时急剧下降,好像系统将过渡到超导状态,但随后饱和到远小于正常状态的值。当施加垂直于薄膜平面的小磁场时,金属中会出现异常金属状态。X0.75电影。发现无序和磁场都可以诱导超导体向异常金属的转变,并且它们对转变的影响是相似的。对于磁场感应的情况,我们发现薄层电阻[RŤHŤH分别是从异常金属到超导体的交叉点附近以及在异常金属到绝缘子过渡点附近的数据分别服从Bose-金属模型推导的唯一缩放定律。我们的结果有力地表明,X二氧化硅21个-X 粒状膜是玻色的,超导量子涨落引起的动态规格场涨落在其形成中起关键作用。
更新日期:2020-12-03
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