Signatures of pressure induced superconductivity in insulating Bi2212

We have performed several high pressure electrical resistance experiments on Bi1.98Sr2.06Y0.68Cu2O8, an insulating parent compound of the high-Tc Bi2212 family of copper oxide superconductors. We find a resistive anomaly, a downturn at low temperature, that onsets with applied pressure in the 20-40 kbar range. Through both resistance and magnetoresistance measurements, we identify this anomaly as a signature of induced superconductivity. Resistance to higher pressures decreases Tc, giving a maximum of 10 K. The higher pressure measurements exhibit a strong sensitivity to the hydrostaticity of the pressure environment. We make comparisons to the pressure induced superconductivity now ubiquitous in the iron arsenides.Comment: 5 pages, 4 figures, submitted to Phys. Rev.

A SIMPLE METHOD FOR ASSESSMENT OF MUSCLE MECHANICAL CAPACITIES FROM FUNCTIONAL MOVEMENT TASKS

The aim of the present study was to evaluate the level of agreement between the routinely used multiple-load method and a simple two-load method based on direct assessment of the F-V relationship from only 2 external loads applied. Twelve participants were tested on the maximum performance vertical jumps, cycling, bench press throws, and bench pull performed against a variety of different loads. All four tested tasks revealed both exceptionally strong relationships between the parameters of the 2 methods (median R = 0.98) and a lack of meaningful differences between their magnitudes (fixed bias below 3.4%). Therefore, addition of another load to the standard tests of various functional tasks typically conducted under a single set of mechanical conditions could allow for the assessment of the muscle mechanical properties, such as the muscle F, V, and P producing capacities

Uncovering a pressure-tuned electronic transition in BiSrYCu2O8 using Raman scattering and x-ray diffraction

We report pressure tuned Raman and x-ray diffraction data of Bi1.98Sr2.06Y0.68Cu2O8 revealing a critical pressure at 21 GPa with anomalies in six physical quantities: electronic Raman background, electron-phonon coupling, spectral weight transfer from high to low frequency, density dependent behaviour of phonon and magnon frequencies, and a compressibility change in the c-axis. For the first time in a cuprate, mobile charge carriers, lattice, and magnetism all show anomalies at a distinct critical pressure in the same experimental setting. Furthermore, the Raman spectral changes are similar to that seen traversing the superconducting dome with doping, suggesting that the critical pressure at 21 GPa is related to the much discussed critical point at optimal doping.Comment: 5 pages, 4 figures, submitted to PR

Coupling Of The B1g Phonon To The Anti-Nodal Electronic States of Bi2Sr2Ca0.92Y0.08Cu2O(8+delta)

Angle-resolved photoemission spectroscopy (ARPES) on optimally doped Bi2Sr2Ca0.92Y0.08Cu2O(8+delta) uncovers a coupling of the electronic bands to a 40 meV mode in an extended k-space region away from the nodal direction, leading to a new interpretation of the strong renormalization of the electronic structure seen in Bi2212. Phenomenological agreements with neutron and Raman experiments suggest that this mode is the B1g oxygen bond-buckling phonon. A theoretical calculation based on this assignment reproduces the electronic renormalization seen in the data.Comment: 4 Pages, 4 Figures Updated Figures and Tex

Multiple Bosonic Mode Coupling in Electron Self-Energy of (La_2-xSr_x)CuO_4

High resolution angle-resolved photoemission spectroscopy data along the (0,0)-($\pi$,$\pi$) nodal direction with significantly improved statistics reveal fine structure in the electron self-energy of the underdoped (La$_{2-x}$Sr$_x$)CuO$_4$ samples in the normal state. Fine structure at energies of (40$\sim$46) meV and (58$\sim$63)meV, and possible fine structure at energies of (23$\sim$29)meV and (75$\sim$85)meV, have been identified. These observations indicate that, in LSCO, more than one bosonic modes are involved in the coupling with electrons.Comment: 4 pages, 3 figures, Fig. 2 update

Doping dependence of the coupling of electrons to bosonic modes in the single-layer high-temperature Bi2Sr2CuO6 superconductor

A recent highlight in the study of high-Tc superconductors is the observation of band renormalization / self-energy effects on the quasiparticles. This is seen in the form of kinks in the quasiparticle dispersions as measured by photoemission and interpreted as signatures of collective bosonic modes coupling to the electrons. Here we compare for the first time the self-energies in an optimally doped and strongly overdoped, non-superconducting single-layer Bi-cuprate (Bi2Sr2CuO6). Besides the appearance of a strong overall weakening, we also find that weight of the self-energy in the overdoped system shifts to higher energies. We present evidence that this is related to a change in the coupling to c-axis phonons due to the rapid change of the c-axis screening in this doping range.Comment: 4 pages, 3 figure

Low-Energy Electronic Structure of the High-Tc Cuprates La2-xSrxCuO4 Studied by Angle-resolved Photoemission Spectroscopy

We have performed a systematic angle-resolved photoemission spectroscopy (ARPES) study of the high-Tc cuprates La2-xSrxCuO4, ranging from the underdoped insulator to the superconductor to the overdoped metal. We have revealed a systematic doping evolution of the band dispersions and (underlying) Fermi surfaces, pseudogap and quasi-particle features under the influence of strong electron-electron interaction and electron-phonon interaction. The unusual transport and thermodynamic properties are explained by taking into account the pseudogap opening and the Fermi arc formation, due to which the carrier number decreases as the doped hole concentration decreases.Comment: 27 pages, 17 figures, accepted in Journal of Physics Condensed Matte