Irlandés,
Yes, a phase angle of 0-degree is theoretically possible, and it should prove to be extremely efficient due to faster control response and minimal cross-coupling.
Rotors that are articulated at the center of the mast and teetering rotors (without delta3 - such as the Robinson's have) have a 90-degree phase lag. So called rigid rotors and rotors with offset hinges have a phase lag of less than 90-degrees.
The
Sikorsky ~ XH-59A ABC had a flight adjustable swashplate phase angle with a range from 0 to 70-degrees.
The UniCopter that I am developing has a phase angle of 0-degrees (I.e. no phase lag).
More information on Phase Angle