Signatures of the attractive interaction in spin spectra of one-dimensional cuprate chains

Identifying the minimal model for cuprates is crucial for explaining the high-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>T</a:mi><a:mi>c</a:mi></a:msub></a:math> pairing mechanism. Recent photoemission experiments have suggested a significant near-neighbor attractive interaction <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mi>V</b:mi></b:math> in cuprate chains, favoring pairing instability. To determine its strength, we systematically investigate the dynamical spin structure factors <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mi>S</c:mi><c:mo>(</c:mo><c:mi>q</c:mi><c:mo>,</c:mo><c:mi>ω</c:mi><c:mo>)</c:mo></c:mrow></c:math> using the density matrix renormalization group. Our analysis quantitatively reveals a notable softening in the two-spinon continuum, particularly evident in the intense spectrum at large momentum. This softening is primarily driven by the renormalization of the superexchange interaction, as determined by a comparison with the slave-boson theory. We also demonstrate the feasibility of detecting this spectral shift in thin-film samples using resonant inelastic x-ray scattering. Therefore, this provides a distinctive fingerprint for the attractive interaction, motivating future experiments to unveil essential ingredients in cuprates. Published by the American Physical Society 2024