Transport Properties Of Thin Films With Two Dimension Periodic Structure In Superconducting Critical Region

Superconductors are diamagnetic.The flux will get into the superconductor the at the superconducting transition region and the movement of the magnetic flux will be the main factors affecting its resistance.For a superconducting thin film with a twodimensional periodic structure,the topological structure of the superconducting thin film is the main factor affecting the variation of the magnetoresistance.As a means to study the collective response of the system,the transport measurement can indirectly explain the movement and distribution of the magnetic flux in the superconductor.This paper mainly introduces the preparation methods of micro nano processing with different hole array two-dimensional structure,the effects of different structure for the transition curve of transmission measurement reluctance by electromagnetic transport properties,and the various structures to speculate in superconductor flux.In this paper,the experimental phenomena are divided into two parts.The effect of the oscillation is called the matching effect,that is,in the specific magnetic field conditions,there will be a minimum resistance,which is called the matching field.These specific magnetic fields are generally periodic,and the specific performance is that the matching field is an integer multiple of the minimum matching field(the first matched field).Although the oscillation effect is similar,there are different mechanisms.When the gap between the hole is large,because of the magnetic flux quantization effect,the flux in the superconductor is an integer multiple of the magnetic flux quantum.Mutual exclusion between the flux,with pinning centers(usually in a superconductor impurity or defect)in superconductors is affected by the pinning force.In the case of small magnetic field,magnetic flux are pinned in the pinning center because of the pinning force and potential.When the pinning center is periodic,the magnetic flux bound to each pinning point is an integer multiple of the magnetic flux quanta,and the interaction force between the magnetic flux is counteracted to form a stable structure.When the magnetic field is added,the resistance of the superconductor is due to the reverse voltage caused by the movement of the magnetic flux.When there is transport current in a superconductor with periodic pinning centers,despite the Lorenz force,the pinning potential due to the existence of the pinning force and Lorenz force in the opposite direction,offset each other,in the field,the interaction between the magnetic flux offset,join force is 0,the flux in a stable state.The resistance of the superconductor is minimum.The experimental results verify the matching effect of the magnetoresistance curves.However,with the increase of the magnetic field,the period of the magnetoresistance curve changes,and the overall decline of the magnetoresistance curve,which provides evidence for the entry of the gap flux.The change of the matching field period is due to the entry of the gap flux,which causes the periodic change of the magnetic flux lattice,and the overall decline of the magnetic resistance curve is due to the fact that the flux of the gap is further bound to the flux.The second part is about the fractional matching effect.In the experiment fractional matching field are found in different samples.The ratio of fractional matching field with the first field matching is determined by structure of the arrays,the model of viewing flux as a particle cannot explain the phenomenon.The differences between the circular periodic array with other pinning centers is that the minimum gap between the hole and the superconductor coherent length is similar as the correlation length,superconducting order parameter does not change significantly between the holes,so to use the fluxoid instead of quantized magnetic flux.At the same time,the smaller gap region is regarded as a line,the larger gap region is regarded as a node,and the circular hole array is simplified into a line like network structure.The theoretical calculation results of the line like network are in good agreement with the experimental phenomena.