In this talk I review the recent theoretical approach to the theory of high temperature superconductors, which considers the SU(2) rotation between d-wave pairing and the charge sector as a main player in the physics of these compounds [1-4]. We first discuss the role of this symmetry in the physics of the pG phase, its relation with AFM fluctuations and the recently observed charge orders in the under doped regime. We show recent numerical findings suggesting that the splitting of the SU(2) symmetry is minimal for a wide range of parameters, and gets smaller and smaller as the coupling is increased [4]. We argue that the collective mode associated with this symmetry corresponds to the A1g resonance observed in Raman scattering at 41 meV around optimal doping.

[1] K.B.Efetov, H.Meier & C.Pépin, Nat. Phys. 9, 442 (2013).
[2] H.Meier, M.Einenkel, C.Pépin & K.B.Efetov, PRB 88, 020506; PRB 89,195115 (2014).
[3] C.Pépin, V. S.de Carvalho, T.Kloss & X.Montiel, PRB 90, 195207 (2014).
[4] T.Kloss, X.Montiel & C.Pépin, arXiv:1501.05324