  In-situ hydrostatic and uniaxial high pressure studies were performed on
recently discovered CrAs-based qausi-one-dimensional superconductors A2Cr3As3
(A=K and Rb). The established Pressure-Temperature phase diagram in this study
clearly demonstrates that either hydrostatic pressure or uniaxial pressure
globally suppresses the superconducting transition temperature (Tc), and the
latter is more effective than the former. Interestingly, in the same
hydrostatic pressure environment, the suppressing rate of Tc in Rb2Cr3As3 is
nearly twice as that of K2Cr3As3. Significantly, the reduced Tc in these
superconductors can fully recover to its ambient-pressure value after the
applied pressure is entirely released. Our results suggest that the bonding
distance and angle between Cr-Cr in the Cr3As3 chains are the key factor in
determining Tc and that the optimal lattice for superconductivity is hosted in
the pristine K2Cr3As3.
