Electrically controlled quantum transition to an anomalous metal at LaVO₃/SrTiO₃ interfaces

Superconductivity (SC) in low-dimensional, low-carrier density systems is fascinating due to deviation of electron pairing mechanism from conventional BCS-Eliashberg paradigm. Insight can be gained into mechanism of emergence of SC in such systems by studying the destruction of SC through controlled disordering. We have shown that an array of well segregated superconducting islands, embedded in a semiconducting (bad metallic) matrix, can be reproducibly constructed and controllably tuned in-situ by an electric field at LaVO₃/SrTiO₃ interfaces. By controlling an electric field V_G (hence disorder), a quantum phase transition from a superconducting phase to a strange quantum anomalous metallic (QAM) phase is accomplished. In the QAM phase, the resistivity drops below a critical temperature and then saturates, indicating possibility of emergence of a Bose metal like phase. The unprecedented control over the distribution of nanometer-scale superconducting islands is obtained through the control of nanometer-scale ferroelectric domains formed in the SrTiO₃ side of the interface due to a low-temperature structural phase transition. This opens a new avenue to realize novel quantum phases in low-dimensional materials through in-situ domain engineering.