%0 Journal Article
%T The Influence of Electron Transfer on <i>T</i><i><sub>c</sub></i> in Superconductors
%A Joachim Sonntag
%J World Journal of Condensed Matter Physics
%P 128-139
%@ 2160-6927
%D 2024
%I Scientific Research Publishing
%R 10.4236/wjcmp.2024.144011
%X <i>Increase</i> of <i>T</i><i><sub>c</sub></i> in Al<sub>1</sub><sub>&#8722;</sub><i><sub>x</sub></i>(SiO<sub>2</sub>)<i><sub>x</sub></i> cermets with increasing <i>x</i> is caused by electron transfer from the Al grains to the SiO<sub>2</sub> phase occupying surface states, expressed by <math xmlns='http://www.w3.org/1998/Math/MathML'>
 <mrow>
  <mrow><mrow>
   <msub>
    <mi>T</mi>
    <mi>c</mi>
   </msub>
   </mrow><mo>/</mo><mrow>
   <msub>
    <mi>T</mi>
    <mrow>
     <mi>c</mi><mo>,</mo><mi>max</mi></mrow>
   </msub>
   </mrow></mrow>
  <mo>=</mo><mn>1</mn><mo>&#x2212;</mo><mi>&#x03B3;</mi><mo>&#x22C5;</mo><msup>
   <mi>n</mi>
   <mn>2</mn>
  </msup>
  </mrow>
</math>

 (*), where <i>n</i> is the electron density in the Al phase and <math xmlns='http://www.w3.org/1998/Math/MathML'>
 <mi>&#x03B3;</mi>
</math>

 a characteristic parameter. <i>Decrease</i> of <i>T</i><i><sub>c</sub></i> in Pb-Cu-sandwiches is attributed to the electron transfer from the Cu film to the Pb film. <math xmlns='http://www.w3.org/1998/Math/MathML'>
 <mi>&#x03B3;</mi>
</math>

 and <math xmlns='http://www.w3.org/1998/Math/MathML'>
 <mrow>
  <msub>
   <mi>T</mi>
   <mrow>
    <mi>c</mi><mo>,</mo><mi>max</mi></mrow>
  </msub>
  </mrow>
</math>

 in equation (*) stands for the influence of the electron-phonon interaction and <math xmlns='http://www.w3.org/1998/Math/MathML'>
 <mrow>
  <msup>
   <mi>n</mi>
   <mn>2</mn>
  </msup>
  </mrow>
</math>

 for the influence of the electron-electron Coulomb repulsion on <i>T</i><i><sub>c</sub></i>. The result that equation (*) holds for both hole-doped cuprate high-temperature superconductivity (HTSC) and Al<sub>1</sub><sub>&#8722;</sub><i><sub>x</sub></i>(SiO<sub>2</sub>)<i><sub>x</sub></i> cermets is an important indication that common mechanisms underlie HTSC and classical superconductors. The difference between the two is that in HTSC, electron transfer occurs between different electronic bands, but in Al<sub>1</sub><sub>&#8722;</sub><i><sub>x</sub></i>(SiO<sub>2</sub>)<i><sub>x</sub></i> cermets between different phases.
%K High-Tc Superconductor
%K Electron Transfer
%K Electron Density
%K Hole Density
%K Cooper Pairs
%K Cermets
%K Granular Metals
%K Metal-Metal Sandwiches
%U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=137761