Magnetic quantum phase transition at the pseudogap boundary in $La{1.8-x}Eu{0.2}Sr{x}CuO{4}$ in high fields

We have performed NMR measurements in $La_{1.8-x}Eu_{0.2}Sr_{x}CuO_{4}$ for x values close to the critical hole doping p* = 0.24 of the pseudogap phase at T = 0, in high magnetic fields intense enough to quench superconductivity. The data reveal that the non-superconducting ground state changes from an antiferromagnetic order (more precisely an incommensurate antiferromagnet that freezes like a glass and competes with superconductivity) to a fluctuating antiferromagnet. Furthermore, this quantum phase transition appears to coincide with the pseudogap boundary p*. These results raise the question as to whether the sharp changes in electronic properties (electronic specific heat, angle-dependent magnetoresistance and electrical conductivity) observed at p* in this class of cuprates more directly originate from the pseudogap state or from this magnetic quantum phase transition.