Quantum-limit linkage of 'strange' and conventional metal states of high-Tc superconductors

Highlights: • High magnetic field transport in high-Tc cuprate superconductors. • Field-temperature-doping map of the pseudogap state. • Crossover from non-Fermi-liquid to the conventional Fermi liquid in the overdoped regime. • Strange metal regime and magnetic field dependent quantum critical point. -- Abstract: The key to the nature of superconducting pairing in high-Tc cuprates lies in understanding the transition to a conventional behavior when they are heavily doped. By using high magnetic fields, we show that the pseudogapped Tl2Ba2CuO6+x becomes a conventional metal at heavy doping in a quantum phase transition, where the pseudogap boundary develops a thermodynamic divergence corresponding to a zero entropy jump. The critical doping point downshifts with magnetic field in unison with the suppression of Tc. This implies that quantum critical fluctuations and magnetic degrees that destabilize the pseudogap are linked to the superconductivity with high Tc