Partial and macroscopic phase coherences in an underdoped Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} thin film

Abstract

A combined study using the time-resolved pump-probe technique and the time domain terahertz transmission spectroscopy has been carried out to investigate the normal-state anomalies in underdoped Bi2Sr2CaCu2O8 + δ. It was observed that a superconducting gap and a pseudogap coexist in the superconducting state. The pseudogap locally evolves below T* ≃ 210 K simultaneously with the appearance of partial phase coherence with a short lifetime less than 1 ps. With decreasing temperature, the domains with a pseudogap developed and saturated at TS ∼ 95 K, and the frequency-dependent superconductivity fluctuation appeared as cooperative phenomena among the partial phase-coherent domains. These experimental data show that the development of the partial coherent local domains with a pseudogap has an important role to switch from the partial to the macroscopic phase-coherent state.

Quasiparticle relaxation dynamics in underdoped Bi2Sr2CaCu2OToda1, Mertelj2, Kusar3 et al. 2011Phys. Rev. B

“…This featureless T dependence is also consistent with τ PG observed in other cuprates. 7,[13][14][15][16][17][18][19][20][21][22] The decay time of R/R at E pr b (triangles), where we expect the single PG component above T c , is also plotted in Fig. 3(b).…”

“…Let us briefly comment on the selectivity of SC/PG component in the optical pump-probe measurement. In cuprates superconductors, a two-component signal consisting of SC and PG components has been widely observed, [12][13][14][16][17][18][19] where the magnitude of the signal reflects the change of the interband transition probabilities induced by the photoexcited QPs. 17 Since the transition probability depends on the probe energy and polarization, we can enhance/suppress one of the SC/PG components by changing the excitation condition.…”

“…ists with the native SC component, as has been demonstrated in the previous papers. 7,[13][14][15][16][17][18][19][20][21][22]27 In Figs. 4(c) 6 we determine the saturation threshold fluence F th by the value at which R/R reaches 2λ/(1 + 2λ)/(1 + ρ −2 ) of the maximum of R/R, where λ = λ pu /λ pr , with optical penetration depths for pump (λ pu ) and probe (λ pr ), and ρ = ρ pu /ρ pr , with beam radii for pump (ρ pu ) and probe (ρ pr ).…”

“…A theoretical framework for analyzing the transient data has being established on the basis of comprehensive and systematic experiments on various superconductors 5,[8][9][10][11] involving BCS-type, 12 cuprates, 6,7,[13][14][15][16][17][18][19][20][21][22][23][24][25][26] Fe-based superconductors, 27 and other related compounds. 28 In the cuprates, the distinction of the QP dynamics between SC and PG has been realized by the characteristics of each dynamics, such as relaxation time, temperature dependence, [12][13][14][16][17][18][19] or dependence on the external fields. 20 The differences in transition probability and matrix elements for optical probe transitions also provide a possibility to selectively enhance the QP dynamics detection of SC/PG, which allows us to analyze each dynamics individually.…”

Spin Polaron-Bipolaron Scenario of Three Gap-Like Energy Scales in Superconducting Cuprates

“…The term pseudogap has been coined to describe this kind of physics. The presence of pseudogap has been established through the measurements of the nuclear magnetic resonance (NMR) [5], the scanning tunneling spectroscopy [6][7][8][9], the analysis of the electronic Raman scattering [10][11][12], through time-resolved optical spectroscopy [13][14][15][16][17][18], and through the ARPES [19][20][21][22][23][24][25]. The observed strong Nernst effect in cuprates has been also attributed to it [26][27][28].…”