Direct Observation of the Coexistence of the Pseudogap and Superconducting Quasiparticles inBi2Sr2CaCu2O8+yby Time-Resolved Optica

Abstract

We report the ultrafast optical response of quasiparticles (QPs) in both the pseudogap (PG) and superconducting (SC) states of an underdoped Bi2Sr2CaCu2O8 + y (Bi2212) single crystal measured with the time-resolved pump-probe technique. At a probe energy variant planck's over omegapr = 1.55 eV, it is found that the reflectivity change DeltaR/R changes its sign at exactly Tc, which allows the direct separation of the charge dynamics of PG and SC QPs. Further systematic investigations indicate that the transient signals associated with PG and SC QPs depend on the probe beam energy and polarization. By tuning them below Tc, two distinct components can be detected simultaneously, providing evidence for the coexistence of PG and SC QPs.

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

“…They then reach equilibrium by high-frequency phonon decay. 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. 17,22 In our previous paper, we selectively isolated the transient dynamics associated with SC and PG QPs in UD-Bi2212 by changing the probe beam energy and polarization. 22 We also showed that two distinct components can be detected simultaneously below T c .…”

“…17,22 In our previous paper, we selectively isolated the transient dynamics associated with SC and PG QPs in UD-Bi2212 by changing the probe beam energy and polarization. 22 We also showed that two distinct components can be detected simultaneously below T c . However, the paper lacked quantitative details.…”

Ultrafast pump-probe spectroscopic signatures of superconducting and pseudogap phases in YBa2Cu3O7−δ films

“…9,11,25,26 This fundamental discrepancy was attributed to the dependence of ΔR/R on several factors including laser power, 15,23 wavelength, 25,27 polarization, 25,28 and repetition rate 24,29 . Furthermore, in a recent effort to uncover the transient optical signatures of the pseudogap (PG) phase, [11][12][13][14]28,[30][31][32] and elucidate a possible relationship between the PG state and SC state in OD YBCO [31][32] , the PG phase was either identified as a weak transient feature 11,30 or found to be completely absent from the spectra. 9,19,25,26 Here, we report on a new procedure to obtain the definitive ultrafast optical RT model.…”

Pump- and Probe-polarization Analyses of Ultrafast Carrier Dynamics in Organic Superconductors

“…them [1][2][3][4][5][6]. Recently, in the cuprate superconductor Bi 2 Sr 2 CaCu 2 O 8+δ the detailed research on the probe-polarization dependence of the carrier dynamics has revealed that the observed polarization anisotropy arises from spontaneous symmetry breaking (SB) in the superconducting and pseudogap phases [7].…”