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The recent discovery of pressure induced superconductivity in the binary helimagnet CrAs has attracted much attention. How superconductivity emerges from the magnetic state and what is the mechanism of the superconducting pairing are two important issues which need to be resolved. In the present work, the suppression of magnetism and the occurrence of superconductivity in CrAs as a function of pressure ($p$) were studied by means of muon spin rotation. The magnetism remains bulk up to $psimeq3.5$~kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at $psimeq$7~kbar. At 3.5 kbar superconductivity abruptly appears with its maximum $T_c simeq 1.2$~K which decreases upon increasing the pressure. In the intermediate pressure region ($3.5lesssim plesssim 7$~kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature ($T_c$) and of the superfluid density ($rho_s$). A scaling of $rho_s$ with $T_c^{3.2}$ as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.
We report resistivity measurements of the helimagnet CrAs under pressures. The helimagnetic transition with T_N ~ 265 K at ambient pressure is completely suppressed above a critical pressure of P_c ~ 0.7 GPa, and superconductivity is observed at ~2.2
We investigate the pressure and temperature dependence of the lattice dynamics of the underdoped, stoichiometric, high temperature superconductor YBa2Cu4O8 by means of Raman spectroscopy and ab initio calculations. This system undergoes a reversible
$^{75}$As, $^{87}$Rb and $^{85}$Rb nuclear quadrupole resonance (NQR) and $^{87}$Rb nuclear magnetic resonance (NMR) measurements in RbFe$_2$As$_2$ iron-based superconductor are presented. We observe a marked broadening of $^{75}$As NQR spectrum belo
We have constructed a pressure$-$temperature ($P-T$) phase diagram of $P$-induced superconductivity in EuFe$_2$As$_2$ single crystals, via resistivity ($rho$) measurements up to 3.2 GPa. As hydrostatic pressure is applied, an antiferromagnetic (AF) t
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 temperatur