Optical studies of high-temperature superconducting cuprates

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Physics

Background:

• High-temperature superconducting cuprates (HTSC) exhibit complex electronic behaviors.
• Understanding their transition from insulating to metallic states is crucial.
• Optical spectroscopy is a powerful tool for probing electronic properties.

Purpose of the Study:

• To review optical studies of HTSC.
• To elucidate the electronic state transitions and dimensionality.
• To investigate phenomena related to the pseudogap and superconductivity.

Main Methods:

• Analysis of doping dependence of room temperature optical spectra.
• Examination of temperature dependence of optical spectra.
• Review of experimental discoveries using optical measurements.

Main Results:

• Revealed a dramatic electronic state change from Mott (charge transfer) insulator to Fermi liquid with doping.
• Identified the unusual two-dimensional (2D) nature of the electronic state.
• Provided insights into pseudogap, superconducting gap, Josephson plasmons, and transverse Josephson plasma modes.
• Discovered Josephson plasmons and transverse Josephson plasma modes unique to HTSC via optical methods.
• Highlighted the role of spin/charge stripe order and its anisotropic pair-breaking effect.

Conclusions:

• Optical studies are essential for understanding HTSC electronic properties.
• HTSC exhibit unique electronic states and phenomena, including stripe order.
• Josephson plasmons and transverse Josephson plasma modes are distinct features of HTSC discovered through optical measurements.