Superconducting junction element and superconducting junction circuit

Abstract

A superconducting junction element has a lower electrode formed by a superconductor layer, a barrier layer provided on a portion of a surface of the lower electrode, an upper electrode formed by a superconductor and covering the barrier layer, and a superconducting junction formed by the lower electrode, the barrier layer and the upper electrode. A critical current density of the superconducting junction is controlled based on an area of the lower electrode.

1 . A superconducting junction element comprising: 
 a lower electrode formed by a superconductor layer;    a barrier layer provided on a portion of a surface of the lower electrode;    an upper electrode formed by a superconductor and covering the barrier layer; and    a superconducting junction formed by the lower electrode, the barrier layer and the upper electrode,    wherein a critical current density of the superconducting junction is controlled based on an area of the lower electrode.    
   
   
       2 . The superconducting junction element as claimed in  claim 1 , wherein the lower electrode has a rectangular shape.  
   
   
       3 . The superconducting junction element as claimed in  claim 2 , wherein the critical current density of the superconducting junction is controlled based on a width and/or a depth of the lower electrode.  
   
   
       4 . The superconducting junction element as claimed in  claim 1 , further comprising: 
 a superconducting magnetic shielding layer that is grounded; and    an insulator layer provided on the superconducting magnetic shielding layer,    wherein the superconducting magnetic shielding layer is electrically connected to the lower electrode via a contact hole provided in the insulator layer.    
   
   
       5 . The superconducting junction element as claimed in  claim 4 , wherein the critical current density of the superconducting junction is further controlled based on an area of the contact hole.  
   
   
       6 . The superconducting junction element as claimed in  claim 1 , wherein each of the upper and lower electrodes is made of an oxide superconductor material.  
   
   
       7 . A superconducting junction circuit which uses a signal of a flux quantum as a carrier, comprising: 
 a lower electrode formed by a superconductor layer;    a barrier layer provided on a portion of a surface of the lower electrode;    an upper electrode formed by a superconductor and covering the barrier layer; and    a plurality of superconducting junctions each formed by a corresponding lower electrode and barrier layer and the upper electrode,    wherein a critical current density of the superconducting junction is controlled based on an area of the lower electrode.    
   
   
       8 . The superconducting junction circuit as claimed in  claim 7 , wherein areas of the lower electrodes forming the superconducting junctions are substantially the same.  
   
   
       9 . The superconducting junction circuit as claimed in  claim 7 , wherein shapes of the lower electrodes forming the superconducting junctions are substantially the same.  
   
   
       10 . The superconducting junction circuit as claimed in  claim 7 , wherein the lower electrodes forming the superconducting junctions have a rectangular shape.  
   
   
       11 . The superconducting junction circuit as claimed in  claim 10 , wherein the critical current density of each of the superconducting junctions is controlled based on a width and/or a depth of the corresponding lower electrode.  
   
   
       12 . The superconducting junction circuit as claimed in  claim 11 , wherein widths of the lower electrodes of the superconducting junctions have an average value Avg 1  and a standard deviation σ 1 , and a ratio σ 1 /Avg 1  is set in a range of 0 to 23%.  
   
   
       13 . The superconducting junction circuit as claimed in  claim 12 , wherein depths of the lower electrodes of the superconducting junctions have an average value Avg 2  and a standard deviation σ 2 , and a ratio σ 2 /Avg 2  is set in a range of 0 to 23%.  
   
   
       14 . The superconducting junction circuit as claimed in  claim 7 , further comprising: 
 a superconducting magnetic shielding layer that is grounded; and    an insulator layer provided on the superconducting magnetic shielding layer,    wherein the superconducting magnetic shielding layer is electrically connected to the lower electrode via a contact hole provided in the insulator layer.    
   
   
       15 . The superconducting junction circuit as claimed in  claim 14 , wherein the critical current density of each of the superconducting junctions is further controlled based on an area of a corresponding contact hole.  
   
   
       16 . The superconducting junction circuit as claimed in  claim 14 , further comprising: 
 a lower electrode connecting layer formed by a superconductor layer and electrically connecting a plurality of lower electrodes.    
   
   
       17 . The superconducting junction circuit as claimed in  claim 16 , wherein the lower electrode connecting layer is provided on the lower electrodes.  
   
   
       18 . The superconducting junction circuit as claimed in  claim 16 , wherein a plurality of said lower electrode connecting layers are provided with respect to the lower electrodes, and the lower electrode connecting layers electrically connect mutually different lower electrodes.  
   
   
       19 . The superconducting junction circuit as claimed in  claim 14 , wherein an area of the contact hole is 100 μm 2  or less and greater than 0.  
   
   
       20 . The superconducting junction circuit as claimed in  claim 7 , wherein each of the upper and lower electrodes is made of an oxide superconductor material.  
   
   
       21 . The superconducting junction circuit as claimed in  claim 14 , wherein the superconducting magnetic shielding layer is made of an oxide superconductor material.  
   
   
       22 . The superconducting junction circuit as claimed in  claim 16 , wherein the lower electrode connecting layer is made of an oxide superconductor material.  
   
   
       23 . A superconducting junction circuit comprising: 
 a plurality of lower electrodes formed by a superconductor layer;    a barrier layer provided on a portion of a surface of each of the plurality of lower electrodes;    at least one upper electrode formed by a superconductor and covering each barrier layer; and    a plurality of superconducting junctions each formed by a corresponding lower electrode and barrier layer and the upper electrode,    wherein each of the plurality of lower electrodes has an area that controls a critical current density of a corresponding one of the plurality of superconducting junction to a desired value.