Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

Abstract

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 $p\simeq 3.5$~kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at $p\simeq$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 ($3.5\lesssim p\lesssim 7$~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.

9 pages, 8 figures

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• Structural and Magnetic Phase Diagram of CrAs and its Relationship with Pressure-induced Superconductivity
• Pressure dependence of the magnetic ground states in MnP
• A low-background piston-cylinder type hybrid high pressure cell for muon-spin rotation/relaxation experiments
• Perspective on the muon-spin rotation/relaxation under hydrostatic pressure
• First principles study of structural, magnetic and electronic properties of CrAs
• High pressure magnetic state of MnP probed by means of muon-spin rotation
• Superconductivity and quantum criticality in heavy fermions CeIrSi${}_3$ and CeRhSi${}_3$
• Multiple band-crossings and Fermi surface topology: role of double nonsymmorphic symmetries in MnP-type crystal structures
• Spin-orbit coupling effects on the electronic properties of the pressure-induced superconductor CrAs
• Growth of bulk single-crystal MnP helimagnet and its structural and NMR characterization
• Magnetic tricritical point and nematicity in FeSe under pressure
• High-pressure growth and characterization of bulk MnAs single crystals
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• Structural phases of elemental Gallium: universal relations in type-I superconductors
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• Tunable quantum critical point and detached superconductivity in Al-doped CrAs
• Three-wall piston-cylinder type pressure cell for muon-spin rotation/relaxation experiments
• Magnetism and its coexistence with superconductivity in CaK(Fe${}_{0.949}$Ni${}_{0.051}$)${}_4$As${}_4$: muon spin rotation/relaxation studies
• Magnetic correlations in the pressure-induced superconductor CrAs investigated by ${}^{75}$As nuclear magnetic resonance
• Dimensionality of the superconductivity in the transition metal pnictide WP
• Why paramagnetic chiral correlations in the long wavelength limit do not contribute to muon-spin relaxation