We have developed a consistent theory for the SU(2) emergent symmetry in the under-doped region of the cuprates. We have tested it through various experiments, investigating Inelastic Neutron Scattering, evolution of the pseudo-gap with doping, and most interestingly we made predictions concerning the presence of collective modes of spin zero and charge 2 which would be the signature of the emergent symmetry. The idea of emergent symmetry is interesting and produces strong phenomenology, but to go further we need to strengthen its microscopic basis. That is why we introduced a new concept of two kinds of preformed pairs, in the particle-particle and particle-hole channels, which gets entangled at T*. This is a very new direction for the physics of cuprates, motivated by the very recent observation of a precursor gap in the charge channel ( Raman Scattering on Hg1223) of the same size and variation with doping of the long observed precursor gap in the Cooper pairing channel. The idea of entangled preformed pairs will maybe be able to capture this fascinating competition between the two pairings. The new theory doesn't require an exact SU(2) symmetric ground state, but still is described in terms of a similar O(3) non linear sigma model. The introduction of a new concept, of fractionalized Pair Density Wave in order to explain the formation of a pseudo-gap gives a new viewpoint to this very old mystery of condensed matter physics. This new viewpoint led to the idea that preformed charge two bosons might be present in the strange metal phase, giving rise to anomalous transport and in particular to a linear in T resistivity.
This work has led to 19 publications in peer reviewed scientific journals and one preprint, to three papers disseminating to a general audience, and to an intense dissemination through participation as an invited speaker to 25 international workshops and conferences, four talks to general audiences and the organisation of two workshops.
