Three energy scales in the superconducting state of hole-doped cuprates detected by electronic Raman scattering

摘要

We explore by electronic Raman scattering the superconducting state of the Bi_2Sr_2CaCu_2O_(8+δ) (Bi-2212) crystal by performing a fine-tuned doping study. We find three distinct energy scales in A_(1g), B_(1g), and B_(2g) symmetries which show three distinct doping dependencies. Above p = 0.22, the three energies merge; below p = 0.12, the A_(1g) scale is no longer detectable, while the B_(1g) and B_(2g) scales become constant in energy. In between, the A_(1g) and B_(1g) scales increase monotonically with underdoping, while the B_(2g) one exhibits a maximum at p = 0.16. The three superconducting energy scales appear to be a universal feature of hole-doped cuprates. We propose that the nontrivial doping dependencies of the three scales originate from the Fermi-surface changes and reveal competing orders inside the superconducting dome.