The quasiparticle dynamics with different symmetry further investigated in the superconducting (SC) and normal state of the high-temperature superconductor Bi2Sr2CaCu2O8+δ (Bi2212) using optical pump-probe experiments with different light polarizations at different doping levels. The observation of distinct selection rules for SC excitations present in A1g and B1g symmetries, and for the pseudogap (PG) excitations present in A1g and B2g symmetries by the probe, and absence of any dependence on the pump beam polarization leads to the unequivocal conclusion of the existence of a spontaneous spatial symmetry breaking in the PG state not limited to the sample surface.
COBISS.SI-ID: 27968295
A remarkable change of the quasiparticle relaxation dynamics at the antiferromagnetic transition temperature in iron-based superconductors parent spin-density wave compounds AAs2Fe2 , (A=Ba, Sr, and Eu), observed previously by the near infrared probe, was systematically investigated by broad-band visible time resolved spectroscopy. Two different relaxation processes were identified. The behavior of the slower process, which is strongly sensitive to the magnetostructural transition, was analyzed in the framework of the relaxation-bottleneck model involving magnons. The results were also compared to recent time-resolved angular photoemission results and possible alternative assignment of the slower relaxation to the magnetostructural order parameter relaxation was discussed.
COBISS.SI-ID: 27689767
In this article we have studied nonequilibrium phase transition into the pseudogap state. The three-pulse experiments have revealed short correlation range of the dynamical state and individual character of the quasiparticle relaxation. Energy required for nonthermal destruction of the pseudogap scales linearly with the gap. This is explained with the model which accounts for subgap phonons generation.
COBISS.SI-ID: 28758311
Systems which rapidly evolve through symmetry-breaking transitions on timescales comparable to the fluctuation timescale of the single-particle excitations may behave very differently than under controlled near-ergodic conditions. A real-time investigation with high temporal resolution may reveal insights into the ordering through the transition that are not available in static experiments. We present an investigation of the system trajectory through a normal-to-superconductor transition in a prototype high-temperature superconducting cuprate in which such a situation occurs. Using a multiple pulse femtosecond spectroscopy technique we measure the system trajectory and time evolution of the single-particle excitations through the transition in La1.9Sr0.1CuO4 and compare the data to a simulation based on the time-dependent Ginzburg-Landau theory, using the laser excitation fluence as an adjustable parameter controlling the quench conditions in both experiment and theory. The comparison reveals the presence of significant superconducting fluctuations which precede the transition on short timescales. By including superconducting fluctuations as a seed for the growth of the superconducting order we can obtain a satisfactory agreement of the theory with the experiment. Remarkably, the pseudogap excitations apparently play no role in this process.
COBISS.SI-ID: 29645351
The dynamics of quasi-particle (QP) excitations with different symmetry is investigated in the superconducting (SC) and pseudogap (PG) states of the high-temperature superconductor Bi2Sr2CaCu2O8+d(Bi2212) using a polarization-sensitive optical pump-probe measurement. The observation of distinct anisotropies for SC excitations and for PG excitations by the probe beam polarization and absence of any dependence on the pump beam polarization evidence the existence of a spontaneous spatial symmetry breaking in the PG state
COBISS.SI-ID: 29112103