Uniaxial Strain Dependence of Tc in YBa2Cu3O7:

Internal Strain Induced Intralayer Charge Transfer

W. E. Pickett, Phys. Rev. Lett. 78, 1960 (1997)

Results of ab initio calculations on uniaxially strained YBa2Cu3O7 are correlated with known values of the uniaxial strain dependencies dTc/dj (j = x,y,z) of the superconducting critial temperature Tc. Internal strains are found to dominate the strain dependence, with the strong non-tetragonality correlating directly with the measured non-tetragonality of dTc/dj. Charge rearrangements within the CuO2 layers dominate any chain-to-layer charge transfer and strongly suggest that the relative amount of Cu and O character within the layers determines the strain dependence of Tc.

Calculated Fermi surface that contains the charge carriers in YBa2Cu3O7. The barrels are associated with the CuO2 layers, while the nearly flat sheets arise from the CuO chains.

One perspective of the layered structure of YBa2Cu3O7. Pretend you are an electron in this structure, and next pretend that your are being squeezed. What would you do?