Doping of Ce in T-La2CuO4: Rigorous test for electron-hole symmetry for high-Tc superconductivity

TL;DR

This study successfully doped Ce into T-La2CuO4 using molecular beam epitaxy, revealing that electron doping increases insulating behavior and demonstrating a broken electron-hole symmetry in T-phase high-Tc cuprates.

Contribution

First demonstration of Ce doping in T-La2CuO4 with molecular beam epitaxy, highlighting differences from hole doping and challenging electron-hole symmetry assumptions.

Findings

Ce doping makes T-La2CuO4 more insulating.

Resistivity increases smoothly from hole- to electron-doped regimes.

Electron-hole symmetry is broken in T-phase cuprates.

Abstract

We report that Ce doping was achieved in La2CuO4 with the K2NiF4 (T) structure for the first time by molecular beam epitaxy. A synthesis temperature of as low as ~ 630C and an appropriate substrate choice, i.e., (001)LaSrGaO4 (a \~ 3.843 A), enebled us to incorporate Ce into K2NiF4 lattice and to obtain Ce-doped T-La2-xCexCuO4 up to x ~ 0.06. The doping of Ce makes T-La2CuO4 more insulating, which is in sharp contrast to Sr (or Ba) doping in T-La2CuO4, which make the compound metallic and superconducting. The observed smooth increase in resistivity from the hole-doped side (T-La2-xSrxCuO4) to the electron-doped side (T-La2-xCexCuO4) indicates that the electron-hole symmetry is broken in the T-phase materials.