A major challenge in understanding the cuprate superconductors is to clarify the nature of the fundamental electronic correlations that lead to the pseudogap phenomenon. Here we use ultrashort light pulses to prepare a non-thermal distribution of excitations and capture novel properties that are hidden at equilibrium. Using a broadband (0.5–2 eV) probe, we are able to track the dynamics of the dielectric function and unveil an anomalous decrease in the scattering rate of the charge carriers in a pseudogap-like region of the temperature (T) and hole-doping (p) phase diagram. In this region, delimited by a well-defined T*neq(p) line, the photoexcitation process triggers the evolution of antinodal excitations from gapped (localized) to delocalized quasiparticles characterized by a longer lifetime. The novel concept of photo-enhanced antinodal conductivity is naturally explained within the single-band Hubbard model, in which the short-range Coulomb repulsion leads to a >k-space differentiation between nodal quasiparticles and antinodal excitations.
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机译：了解铜酸盐超导体的主要挑战是弄清导致伪间隙现象的基本电子相关性的本质。在这里，我们使用超短光脉冲准备激发的非热分布，并捕获平衡时隐藏的新特性。使用宽带（0.5–2 eV）探针，我们能够跟踪介电函数的动力学，并揭示出在温度（T）和空穴的伪间隙状区域中载流子散射速率的反常下降。掺杂（p）相图。在该区域中，以明确定义的T * neq（p）线为界，光激发过程触发了反节点激发从缺口（局部化）到离域化准粒子的演化，其特征是寿命更长。在单波段Hubbard模型中自然地解释了光增强反节点电导率的新概念，其中短距离库仑排斥导致节点准粒子与反节点激励之间的> k 空间区分。
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