Scale-invariant magnetoresistance in a cuprate superconductor

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• High-temperature superconducting cuprates exhibit an anomalous metallic state near a quantum critical point, often masked by superconductivity.
• Investigating this metallic state requires suppressing superconductivity, typically with high magnetic fields, but the field's direct impact remains unclear.

Purpose of the Study:

• To investigate the high-field magnetoresistance of thin-film lanthanum strontium copper oxide (La$_{2-x}$Sr$_{x}$CuO$_{4}$) cuprates.
• To understand the direct effect of strong magnetic fields on the anomalous metallic state near the critical doping.

Main Methods:

• Fabrication of thin-film La$_{2-x}$Sr$_{x}$CuO$_{4}$ samples with critical doping levels (0.161 ≤ p ≤ 0.190).
• Measurement of magnetoresistance in ultra-high magnetic fields up to 80 tesla.

Main Results:

• The metallic state, when superconductivity is suppressed, displays magnetoresistance that is linear with magnetic field strength up to 80 tesla.
• The observed linear-in-field resistivity magnitude and doping dependence closely match the linear-in-temperature resistivity associated with quantum criticality in these materials.

Conclusions:

• High magnetic fields reveal a distinct linear magnetoresistance in the metallic state of cuprates near quantum criticality.
• This finding provides a direct link between magnetic field response and temperature-dependent transport, supporting quantum-critical models for high-temperature superconductivity.