Correlation between scale-invariant normal-state resistivity and superconductivity in an electron-doped cuprate

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Critical Phenomena

Background:

• Understanding the normal state of high-temperature superconducting cuprates is key to explaining superconductivity's origin.
• The "strange metal" state, linked to a hidden quantum critical point (QCP), is a focus of research.
• Electron-doped cuprates offer a unique opportunity to study the QCP and the T → 0 K state at low temperatures and fields.

Purpose of the Study:

• To investigate the low-temperature normal-state magnetoresistance (MR) in the electron-doped cuprate system La2-xCexCuO4.
• To probe the quantum critical point (QCP) and its relationship with high-temperature superconductivity.
• To characterize the "strange metal" state in relation to magnetic field and temperature.

Main Methods:

• Measurements of low-temperature normal-state magnetoresistance (MR) were performed on La2-xCexCuO4.
• The study focused on samples with doping (x) above the putative QCP (x = 0.14).
• Analysis involved examining the field and temperature dependence of the magnetoresistance.

Main Results:

• A linear-in-field magnetoresistance behavior was observed for doping above the QCP (x = 0.14).
• This linear MR follows a scaling relation with applied field and temperature.
• The magnitude of the linear MR decreases with decreasing critical temperature (Tc) and vanishes at the end of the superconducting dome (x ~ 0.175), where conventional quadratic MR appears.

Conclusions:

• A strong correlation exists between quantum critical excitations in the strange metal state and high-temperature superconductivity.
• The observed linear magnetoresistance is a signature of the quantum critical point in electron-doped cuprates.
• These findings provide crucial insights into the mechanism of high-temperature superconductivity in cuprates.