  One of the common features of unconventional, magnetically mediated
superconductivity as found in the heavy-fermions, high-transition-temperature
(high-Tc) cuprates, and iron pnictides superconductors is that the
superconductivity emerges in the vicinity of long-range antiferromagnetically
ordered state.[1] In addition to doping charge carriers, the application of
external physical pressure has been taken as an effective and clean approach to
induce the unconventional superconductivity near a magnetic quantum critical
point (QCP).[2,3] Superconductivity has been observed in a majority of 3d
transition-metal compounds,[4-9] except for the Cr- and Mn-based compounds in
the sense that the low-lying states near Fermi level are dominated by their 3d
electrons. Herein, we report on the discovery of superconductivity on the verge
of antiferromagnetic order in CrAs via the application of external high
pressure. Bulk superconductivity with Tc ~ 2 K emerges at the critical pressure
Pc ~ 8 kbar, where the first-order antiferromagnetic transition at TN = 265 K
under ambient pressure is completely suppressed. Abnormal normal-state
properties associated with a magnetic QCP have been observed nearby Pc. The
close proximity of superconductivity to an antiferromagnetic order suggests an
unconventional pairing mechanism for the superconducting state of CrAs. The
present finding opens a new avenue for searching novel superconductors in the
Cr and other transitional-metal based systems.
