[PC1] Cuprates

11:00 AM - 11:15 AM JST(2:00 AM - 2:15 AM UTC)

[PC1-04] Momentum-dependent self-energy revealed by ARPES spectral analysis in La_2-xSr_xCuO₄: mechanism of the universal Fermi velocity

*Teppei Yoshida¹, Daiya Shimonaka¹, Daiki Ootsuki², Atsushi Fujimori³, Hiroshi Kumigashira⁴, Kanta Ono⁵, Seiki Komiya⁶, Yoichi Ando⁷ (1. Kyoto University (Japan), 2. Okayama University (Japan), 3. National Tsing Hua University (Taiwan), 4. Tohoku University (Japan), 5. Osaka University (Japan), 6. Central Research Institute of Electric Power Industry (Japan), 7. University of Cologne (Germany))

Keywords:

ARPES,LSCO,Self-energy,Pseudogap

In high temperature superconductors, it is known that the Fermi velocity along the nodal direction remains independent of doping, a phenomenon referred to as the “universal Fermi velocity” [1]. To elucidate the mechanism of this unusual behavior, we performed a detailed investigation of the self-energy of nodal quasiparticles in La_2-xSr_xCuO₄ using angle-resolved photoemission spectroscopy (ARPES). By applying the Kramers–Kronig(KK) transformation, we precisely analyzed both the energy and momentum dependence of the self-energy. As shown in Figs. 1 (a)(b), we obtained ReG(k, ω) from the KK transformation of ImG(k, ω), where G(k, ω) is a Green’s function. At the same time, the self-energy Σ(k, ω) was obtained as shown in Figs. 1(c)-(e). Particularly, we have experimentally revealed the momentum dependence perpendicular to the Fermi surface, which had previously been overlooked. Our analysis demonstrates that the interplay between the energy and momentum dependences of the self-energy leads to the emergence of the “universal Fermi velocity.” In the underdoped region, a pronounced momentum dependence of the self-energy was observed, which contributes to the reduction of the effective mass. This behavior contrasts with the conventional property of Fermi liquids, where the electron effective mass is typically enhanced. We discuss possible origins of this phenomenon in terms of enhanced antiferromagnetic correlations and/or the exchange term of the Coulomb interaction. These results provide new insights into the electronic states near the Mott insulating regime of high-temperature superconductors.