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Comment on Strain and High Temperature Superconductivity: Unexpected Results from Direct Electronic Structure Measurements in Thin Films

The ARPES measurement on lanthanum system La$_{;2-\delta};$Sr$_\delta$CuO$_4$ (LSCO) \cite{;s, ino}; reveal two important and qualitatively new results: the evolution of the Fermi surface (FS) from hole-like to electron-like, accompanied by the transfer of the spectral weight from the lower to the conducting band upon doping. More specifically, recent ARPES measurements on thin films of LSCO under strain \cite{;s}; show the same topology of the FS as the crystal samples \cite{;ino};, shifted to the smaller values of doping. Quite surprisingly, the change of the topology under strain is accompanied by the drastic change of the bandwidth, deduced from the experimental data. More specifically, at $\delta=0.15$ doping, the bandwidth of the system under strain is almost doubled, compared to the one of the relaxed sample, although the Cu- apex O distance varies by $5 \%$. We argue here that this increase is the artefact of the unappropriate choice of the fitting regime.

effective band-structure; ARPES; LSCO

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