Study of pseudogap and superconducting quasiparticle dynamics in $\rm{Bi_2Sr_2CaCu_2O_{8+\delta}}$ by time-resolved optical reflectivity

X. C. Nie; Hai-Ying Song; Xiu Zhang; Shi-Bing Liu; Yang Wang; Qiang Gao; Lin Zhao; X. J. Zhou; Jian-Qiao Meng; Yu-Xia Duan; H. Y. Liu

doi:10.1016/j.physc.2020.1353710

arXiv · 1803.10506

Study of pseudogap and superconducting quasiparticle dynamics in $\rm{Bi_2Sr_2CaCu_2O_{8+\delta}}$ by time-resolved optical reflectivity

X. C. Nie·Hai-Ying Song·Xiu Zhang·Shi-Bing Liu·Yang Wang·Qiang Gao·Lin Zhao·X. J. Zhou·Jian-Qiao Meng·Yu-Xia Duan·H. Y. Liu

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Abstract

The relation between pseudogap (PG) and superconducting (SC) gap, whether PG is a precursor of SC or they coexist or compete, is a long-standing controversy in cuprate high-temperature supercondutors. Here, we report ultrafast time-resolved optical reflectivity investigation of the dynamic densities and relaxations of PG and SC quasiparticles (QPs) in the underdoped $\rm{Bi_2Sr_2CaCu_2O_{8+\delta}}$ ($T_c$ = 82 K) single crystals. We find evidence of two distinct PG components in the positive reflectivity changes in the PG state, characterized by relaxation timescales of $\tau_{fast}$ $\approx$ 0.2 ps and $\tau_{slow}$ $\approx$ 2 ps with abrupt changes in both amplitudes $A_{fast}$ and $A_{slow}$ at the PG-opening temperature $T^*$. The former presents no obvious change at $T_c$ and coexists with the SC QP. The latter's amplitude starts decreasing at the SC phase fluctuation $T_p$ and vanishes at $T_c$ followed by a negative amplitude signifying the emergence of the SC QP, therefore suggesting a competition with superconductivity.

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X. C. Nie, Hai-Ying Song, Xiu Zhang, Shi-Bing Liu, Yang Wang, Qiang Gao, Lin Zhao, X. J. Zhou, Jian-Qiao Meng, Yu-Xia Duan, H. Y. Liu. 2018-03-28. Study of pseudogap and superconducting quasiparticle dynamics in $\rm{Bi_2Sr_2CaCu_2O_{8+\delta}}$ by time-resolved optical reflectivity. https://doi.org/10.1016/j.physc.2020.1353710

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