  Copper oxide superconductors have continually fascinated the communities of
condensed matter physics and material sciences because they host the highest
ambient-pressure superconducting transition temperature (Tc) and mysterious
physics. Searching for the universal correlation between the superconducting
state and its normal state or neighboring ground state is believed to be an
effective way for finding clues to elucidate the underlying mechanism of the
superconductivity. One of the common pictures for the copper oxide
superconductors is that a well-behaved metallic phase will present after the
superconductivity is entirely suppressed by chemical doping or application of
the magnetic field. Here, we report a different observation of universal
quantum transition from superconducting state to insulating-like state under
pressure in the under-, optimally- and over-doped Bi2212 superconductors with
two CuO2 planes in a unit cell. The same phenomenon has been also found in the
Bi2201 superconductor with one CuO2 plane and the Bi2223 superconductor with
three CuO2 planes in a unit cell. These results not only provide fresh
information but also pose a new challenge for achieving a unified understanding
on the underlying physics of the high-Tc superconductivity.
