Inverse correlation between quasiparticle mass and T c in a cuprate high-T c superconductor

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Superconductivity, particularly high-temperature superconductivity in cuprates, is often linked to quantum phase transitions and competing electronic phases.
• Quantum fluctuations near a zero-temperature transition can enhance electron mass (m*) and drive emergent phenomena like superconductivity.
• In cuprates like YBa2Cu3O7-δ, an increasing m* near optimal doping was observed, suggesting charge order fluctuations might drive high-Tc superconductivity.

Purpose of the Study:

• To investigate the relationship between electron mass (m*) and superconducting transition temperature (Tc) in the cuprate YBa2Cu4O8 under pressure.
• To test the robustness of the correlation observed in YBa2Cu3O7-δ, where increasing m* was linked to higher Tc.
• To determine if quantum fluctuations of charge order enhance superconductivity in YBa2Cu4O8.

Main Methods:

• Quantum oscillation studies were performed on YBa2Cu4O8.
• Hydrostatic pressure was applied to the material to tune its electronic properties.
• The quasiparticle effective mass (m*) and superconducting transition temperature (Tc) were measured under varying pressure conditions.

Main Results:

• In contrast to YBa2Cu3O7-δ, the quasiparticle effective mass (m*) in YBa2Cu4O8 *decreased* as the superconducting transition temperature (Tc) *increased* under pressure.
• This inverse correlation between m* and Tc was observed across a range of applied pressures.
• The findings indicate that while charge order fluctuations might influence electron mass, they do not necessarily enhance the superconducting transition temperature in this material.

Conclusions:

• The observed inverse correlation between electron mass and Tc in YBa2Cu4O8 challenges the proposed mechanism linking enhanced mass due to charge order fluctuations to high-Tc superconductivity in cuprates.
• Quantum fluctuations associated with charge order may not be the universal driver for high-Tc superconductivity.
• Further research is needed to understand the complex interplay between competing phases and superconductivity in cuprates.