Origin of the metal-to-insulator crossover in cuprate superconductors

Understand

Superconductivity in cuprates peaks in the doping regime between a metal at high p and an insulator at low p.

• Understanding how the material evolves from metal to insulator is a fundamental and open question.
• Early studies in high magnetic fields revealed that below some critical doping an insulator-like upturn appears in the resistivity of cuprates at low temperature, but its origin has remained a puzzle.
• Here we propose that this 'metal-to-insulator crossover' is due to a drop in carrier density n associated with the onset of the pseudogap phase at a critical doping p*.