Photostationary Lifshitz transition in High Tc superconductor Bi2Sr2CaCu2O8+δ
To date, controlling the steady-state electronic band structure in high-Tc cuprate superconductors has been achieved primarily through chemical doping or magnetic fields. Here, we present that ultrafast optical excitation can instead drive the electronic band structure of Bi2Sr2CaCu2O8+δ into a photostationary, long-lived excited state. At sufficiently high pump fluences, this state undergoes a Lifshitz transition of the Fermi surface, characterized by a change in topology from hole-like to electron-like. Time- and angle-resolved photoemission spectroscopy, supported by single-band tight-binding calculations, reveals that 1.6 eV photoexcitation induces band-structure evolutions closely analogous to those produced by chemical doping. These results point to an efficient photodoping mechanism involving cooperative effects, including charge transfer, renormalization of effective electronic correlations, and defect-assisted charge trapping. Our findings raise fundamental questions regarding thermalization processes occurring on timescales comparable to the laser repetition period in cuprates. More broadly, ultrafast optical control enables access to otherwise inaccessible regions of the phase diagram by tuning the pump fluence.