Quantum phase transitions in cuprates: stripes and antiferromagnetic supersolids

It is believed that the magnetic fluctuations in cuprate superconductors reflect the proximity to a quantum phase transition. It will be argued that this notion acquires further credibility if combined with the idea that the superconducting state is in a tight competition with the stripe phase over a large range of hole concentrations. On basis of existing data and some simple considerations, a zero-temperature phase diagram will be proposed with an unusual topology which is unique to the competition stripe phase superconductivity. It is argued that the existence of a state which is at the same time stripe ordered and superconducting (antiferromagnetic supersolid) is a prerequisite for quantum critical behavior in the magnetic sector. Various predictions follow which can be tested experimentally. (C) 1999 Elsevier Science B.V. All rights reserved.