New collective mode in YBa_{2}Cu_{3}O_{6+x} observed by time-domain reflectometry (original) (raw)
Related papers
Science
Restoring strangeness Cuprate superconductors host a number of complex phases, and elucidating their relationship to each other may shed light on the nature of cuprate superconductivity. Two of these intriguing phases are the strange metal phase and the charge-density wave (CDW) order, which appear next to each other in the cuprate phase diagram. The hallmark of the strange metal phase, the linear dependence of electrical resistivity on temperature, disappears in the CDW phase. Wahlberg et al . strained thin films of the cuprate YBa 2 Cu 3 O 7–δ to suppress CDW order (see the Perspective by Le Tacon). Using resonant inelastic x-ray scattering and transport measurements, the researchers found that suppressing CDW restored the linear-in-temperature resistivity in the CDW portion of the phase diagram. —JS
X-Ray-Diffraction Study of Charge-Density-Waves and Oxygen-Ordering in YBa2Cu3O6+x Superconductor
We report a temperature-dependent increase below 300 K of diffuse superlattice peaks corresponding to q0= ∼ 2 5 , 0, 0 in an under-doped YBa2Cu3O6+x superconductor (x≈0.63). These peaks reveal strong c-axis correlations involving the CuO2 bilayers, show a non-uniform increase below ∼220 K with a plateau for ∼100-160 K, and appear to saturate in the superconducting phase. We interpret this unconventional T -dependence of the "oxygen-ordering" peaks as a manifestation of a charge density wave in the CuO2 planes coupled to the oxygen-vacancy ordering. 74.72.Bk,61.10.Eq,
Physical Review Letters, 2013
We have used resonant x-ray scattering to determine the momentum dependent charge correlations in YBa2Cu3O6.55 samples with highly ordered chain arrays of oxygen acceptors (ortho-II structure). The results reveal nearly critical, biaxial charge density wave (CDW) correlations at in-plane wave vectors (0.315, 0) and (0, 0.325). The corresponding scattering intensity exhibits a strong uniaxial anisotropy. The CDW amplitude and correlation length are enhanced as superconductivity is weakened by an external magnetic field. Analogous experiments were carried out on a YBa2Cu3O6.6 crystal with a dilute concentration of spinless (Zn) impurities, which had earlier been shown to nucleate incommensurate magnetic order. Compared to pristine crystals with the same doping level, the CDW amplitude and correlation length were found to be strongly reduced.
Physical Review Letters, 2010
We measure the anisotropic mid-infrared response of electrons and phonons in bulk YBa 2Cu3O7−δ after femtosecond photoexcitation. A line shape analysis of specific lattice modes reveals their transient occupation and coupling to the superconducting condensate. The apex oxygen vibration is strongly excited within 150 fs demonstrating that the lattice absorbs a major portion of the pump energy before the quasiparticles are thermalized. Our results attest to substantial electron-phonon scattering and introduce a powerful concept probing electron-lattice interactions in a variety of complex materials. 74.25.Kc, 78.47.jg The interaction of electrons with the crystal lattice represents one of the most elusive, yet pivotal aspects of high-temperature superconductors (HTSCs). Although purely phonon-mediated BCS-type pairing fails to explain essential properties of superconducting (SC) cuprates, convincing evidence of significant electronphonon contributions have been provided by angleresolved photoemission [1-3], inelastic neutron scattering [4], tunneling [5] and Raman [6] spectroscopies. For time-integrated techniques it is difficult, however, to disentangle the interplay between elementary excitations.
Characteristic features of the pseudogap and superconducting states of YBa2Cu3O7−x
Journal of Experimental and Theoretical Physics Letters, 2002
For the past few years, one of the major problems in high-temperature superconductivity (HTSc) has been the study of the physics of the pseudogap state, which exists in the metallic phase at temperatures T * > T c . Today, this problem seems to be among the most topical ones in the physics of high-temperature superconductivity, and its solution will undoubtedly contribute to the elucidation of the microscopic mechanism of HTSc. The width of the pseudogap state region T * -T c in the phase diagram depends on the carrier concentration. It is maximal for underdoped compounds and decreases to zero at a certain critical carrier concentration; the latter is somewhat higher than the concentration at which the critical temperature T c is maximal. Recent theoretical papers suggest an inhomogeneity of the pseudogap phase and the existence of the temperature crossover, which separates the regions of the pseudogap states with different dynamic properties of quasiparticles . Progress in laser technology has made it possible to decrease the laser pulse duration down to a few femtoseconds, and this has opened up new research prospects by making studies of quasiparticle dynamics and lattice vibrations accessible in real time. Such studies, whose typical example is the pumping technique with subsequent probing by two laser pulses separated in time, are actively performed on HTSc systems . The understanding of the mechanism underlying the establishment of equilibrium after its perturbation by a laser pulse gives an insight into the characteristic features of the dynamics of charge carriers and crystal lattice excitations, as well as the dynamics of their interaction. Using the pumping-probing technique, we performed detailed studies of the relaxation dynamics of the lattice and charge carriers in the temperature range covering both superconducting and pseudogap states. The aim of our studies was to determine the degree of homogeneity of the phase diagram region for T > T c and to reveal the characteristic features of the superconducting state.
Physical Review Letters, 2009
By improving the experimental conditions and extensive data accumulation, we have achieved very high-precision in the measurements of the de Haas-van Alphen effect in the underdoped hightemperature superconductor YBa2Cu3O6.5. We find that the main oscillation, so far believed to be single-frequency, is composed of three closely spaced frequencies. We attribute this to bilayer splitting and warping of a single quasi-2D Fermi surface, indicating that c-axis coherence is restored at low temperature in underdoped cuprates. Our results do not support the existence of a larger frequency of the order of 1650 T reported recently in the same compound [S.E. Sebastian et al., Nature 454, 200 (2008)].
Physical Review B
The interaction between phonons and high-energy excitations of electronic origin in cuprates and their role in the superconducting mechanisms is still controversial. Here we use coherent vibrational time-domain spectroscopy together with density functional and dynamical mean-field theory calculations to establish a direct link between the c-axis phonon modes and the in-plane electronic charge excitations in optimally doped YBCO. The non-equilibrium Raman tensor is measured by means of the broadband "coherent-phonon" response in pump-probe experiments and is qualitatively described by our model using DFT in frozen phonon approximation plus single band DMFT to account for the electronic correlations. The major outcome of our experimental and theoretical study is to establish the link between out-of-plane copper ions displacements and the inplane electronic correlations, and to estimate at few unit cells the correlation length of the associated phonon mode. The approach introduced here could help revealing the complex interplay between fluctuations of different nature and spatial correlation in several strongly-correlated materials.
X-ray diffraction study of lattice modulations in an underdoped YBa2Cu3O6+x superconductor
Physical Review B, 2002
We report a temperature-dependent increase below 300 K of diffuse superlattice peaks corresponding to q0= ∼ 2 5 , 0, 0 in an under-doped YBa2Cu3O6+x superconductor (x≈0.63). These peaks reveal strong c-axis correlations involving the CuO2 bilayers, show a non-uniform increase below ∼220 K with a plateau for ∼100-160 K, and appear to saturate in the superconducting phase. We interpret this unconventional T -dependence of the "oxygen-ordering" peaks as a manifestation of a charge density wave in the CuO2 planes coupled to the oxygen-vacancy ordering. 74.72.Bk,61.10.Eq,
Physical Review B, 2011
Microwave absorption measurements in magnetic fields from zero up to 16 T were used to determine the temperature range of superconducting fluctuations above the superconducting critical temperature Tc in YBa2Cu3O 7−δ. Measurements were performed on deeply underdoped, slightly underdoped, and overdoped single crystals. The temperature range of the superconducting fluctuations above Tc is determined by an experimental method which is free from arbitrary assumptions about subtracting the nonsuperconducting contributions to the total measured signal, and/or theoretical models to extract the unknown parameters. The superconducting fluctuations are detected in the ab−plane, and c−axis conductivity, by identifying the onset temperature T ′. Within the sensitivity of the method, this fluctuation regime is found only within a fairly narrow region above Tc. Its width increases from 7 K in the overdoped sample (Tc = 89 K), to at most 23 K in the deeply underdoped sample (Tc = 57 K), so that T ′ falls well below the pseudogap temperature T *. Implications of these findings are discussed in the context of other experimental probes of superconducting fluctuations in the cuprates.
Quantum Oscillations in the Underdoped Cuprate YBa2Cu4O8
Physical Review Letters, 2008
We report the observation of quantum oscillations in the underdoped cuprate superconductor YBa2Cu4O8 using a tunnel-diode oscillator technique in pulsed magnetic fields up to 85 T. There is a clear signal, periodic in inverse field, with frequency 660±15 T and possible evidence for the presence of two components of slightly different frequency. The quasiparticle mass is m * = 3.0 ± 0.3me. In conjunction with the results of Doiron-Leyraud et al. for YBa2Cu3O6.5 [1], the present measurements suggest that Fermi surface pockets are a general feature of underdoped copper oxide planes and provide information about the doping dependence of the Fermi surface.