Electric-field screening

In <a href="/facts/Physics/a7aH2y08">physics</a>, screening is the damping of <a href="/facts/Electric_field/tt4MooBs">electric fields</a> caused by the presence of mobile <a href="/facts/Electric_charge/xxsBfmlB">charge</a> carriers. It is an important part of the behavior of charge-carrying mediums, such as ionized gases (classical <a href="/facts/Plasma_(physics)/1d3btMVU">plasmas</a>), <a href="/facts/Electrolyte/4YE8bIVa">electrolytes</a>, and electronic conductors (<a href="/facts/Semiconductor/zFf3mGTE">semiconductors</a>, <a href="/facts/Metal/PT8hNX6R">metals</a>).
In a fluid, with a given <a href="/facts/Permittivity/Sd3WtgT1">permittivity</a> ε, composed of electrically charged constituent particles, each pair of particles (with charges q1 and q2) interact through the <a href="/facts/Coulomb%27s_law/V0lR5NKv">Coulomb force</a> as

F
        
        =
        
          
            
              
                q
                
                  1
                
              
              
                q
                
                  2
                
              
            
            
              4
              π
              ε
              
                
                  |
                  
                    r
                  
                  |
                
                
                  2
                
              
            
          
        
        
          
            
              
                r
              
              ^
            
          
        
        ,
      
    
    {\displaystyle \mathbf {F} ={\frac {q_{1}q_{2}}{4\pi \varepsilon \left|\mathbf {r} \right|^{2}}}{\hat {\mathbf {r} }},}

where the vector r is the relative position between the charges. This interaction complicates the theoretical treatment of the fluid. For example, a naive quantum mechanical calculation of the ground-state energy density yields infinity, which is unreasonable. The difficulty lies in the fact that even though the Coulomb force diminishes with distance as 1/r2, the average number of particles at each distance r is proportional to r2, assuming the fluid is fairly <a href="/facts/Isotropy/mc3QEY2x">isotropic</a>. As a result, a charge fluctuation at any one point has non-negligible effects at large distances.
In reality, these long-range effects are suppressed by the flow of particles in response to electric fields. This flow reduces the effective interaction between particles to a short-range "screened" Coulomb interaction. This system corresponds to the simplest example of a renormalized interaction.
In <a href="/facts/Solid-state_physics/Cmc6hvyR">solid-state physics</a>, especially for <a href="/facts/Metal/PT8hNX6R">metals</a> and <a href="/facts/Semiconductor/zFf3mGTE">semiconductors</a>, the screening effect describes the <a href="/facts/Electric_field/tt4MooBs">electrostatic field</a> and Coulomb potential of an <a href="/facts/Ion/3bePpDna">ion</a> inside the solid. Like the electric field of the <a href="/facts/Atomic_nucleus/orpIm5Xl">nucleus</a> is reduced inside an atom or ion due to the <a href="/facts/Shielding_effect/PoyU5vNr">shielding effect</a>, the electric fields of ions in conducting solids are further reduced by the cloud of <a href="/facts/Valence_and_conduction_bands/2NUALlHJ">conduction electrons</a>.

Electric-field screening open-in-new

Electric-field screening