Macroscopic evidence for quantum criticality and field-induced quantum fluctuations in cuprate superconductors

Abstract

We present macroscopic experimental evidence for field-induced microscopic quantum fluctuations in different hole- and electron-type cuprate superconductors with varying doping levels and numbers of CuO$_2$ layers per unit cell. The significant suppression of the zero-temperature in-plane magnetic irreversibility field relative to the paramagnetic field in all cuprate superconductors suggests strong quantum fluctuations due to the proximity of the cuprates to quantum criticality.

3 figures. To appear in Phys. Rev. B, Rapid Communications (2007). For correspondence, contact: Nai-Chang Yeh (e-mail: ncyeh@caltech.edu)