Evidence for a photoinduced nonthermal superconducting-to-normal-state phase transition in overdoped Bi2Sr2Ca

Giacomo Coslovich

¹

,

Claudio Giannetti

²

,

Federico Cilento

³

et al.

Abstract

Here we report extensive ultrafast time-resolved reflectivity experiments on overdoped Bi2Sr2Ca1−xYxCu2O 8+δ single crystals (TC =78 K) aimed to clarify the nature of the superconducting-to-normal-state photoinduced phase transition. The experimental data show the lack of the quasiparticles decay time divergence at the fluence required to induce this phase transition, in contrast to the thermally-driven phase transition observed at TC and at variance with recently reported photoinduced charge-density-wave and spin-density-wave to metal phase transitions. Our data demonstrate the non-thermal character of the superconducting-to-normal-state photoinduced phase transition. The data have been analyzed using an ad-hoc developed timedependent Rothwarf-Taylor model, opening the question on the order of this non-equilibrium phase transition.

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

“…The saturation behavior has been observed in various superconductors and ascribed to the destruction of the superconducting condensate. 6,11,24,25 In the present case, the additional positive component appearing at higher F is attributed to the PG that exhibits higher saturation threshold and therefore becomes dominant after the saturation of the SC component. 6 For the comprehensive assignment of coexisting SC and PG components, we show the T dependence of R/R transients at E pu /E pr = 0.95/1.55 eV with F above the saturation condition in Fig.…”

“…24,25 Our data indicate that there is no abrupt changes in the photoinduced reflectivity during the recovery, which would be an indication of the first-order transition. However, the excitation density is, due to the finite penetration depth, highly inhomogeneous and any abrupt changes could be easily smeared out.…”

“…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.…”

Theory of photoexcited carrier relaxation across the energy gap of phase-ordered materials

“…Usually the anomalous T dependence of τ exp is observed in many gapped systems, for example, phaseordered systems showing an energy gap opening in the electron band below the transition temperature T c . It has been found that a wide variety of superconductors [1][2][3][4][5][6][7][8][9][10][11][12][13] and density-wave compounds [14][15][16][17][18][19] show diverging behavior of τ exp near T c , as confirmed by femtosecond time-resolved optical spectroscopy. 1,4,5,[7][8][9][10][11][12][13][14][15][16][17]19 The divergence of τ exp in these gapped systems is believed to result from a recursive energy transfer between electrons and phonons.…”

Superconducting gap inBaFe2(As1−xPx)2from temperature-dependent transient optical reflectivity

“…The saturation behaviour of the transient-reflectivity amplitude with increasing excitation density was observed in a number of gapped systems such as superconductors [8][9][10][11][12][13][14] and charge-density wave compounds 15,16 . The saturation of the transient reflectivity amplitude was associated with a nonthermal destruction of the condensate and complete closure of the gap.…”