Quasiparticle Scattering off Defects and Possible Bound States in Charge-Ordered YBa_{2}Cu_{3}O_{y}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

• Superconductivity and charge-density-wave (CDW) order are competing electronic phases in many materials.
• Understanding the interplay between these phases and the role of defects is crucial for materials design.

Purpose of the Study:

• To investigate the microscopic nature of the charge-density-wave (CDW) state in YBa_{2}Cu_{3}O_{y}.
• To explore the impact of magnetic fields on superconductivity and CDW order.
• To elucidate the role of defects and quasiparticle behavior in the CDW state.

Main Methods:

• Utilizing Nuclear Magnetic Resonance (NMR) spectroscopy to probe the electronic environment.
• Observing ^{17}O Knight shifts under applied magnetic fields.
• Analyzing the distribution of Knight shifts to infer local electronic properties.

Main Results:

• A skewed distribution of ^{17}O Knight shifts was observed when a magnetic field suppressed superconductivity and induced CDW order.
• This skewness indicates an inhomogeneous local density of states N(E_{F}) within the CDW state.
• The findings suggest the formation of quasiparticle bound states due to scattering from unidentified defects.

Conclusions:

• The observed Knight shift distribution provides insight into the microscopic mechanisms of CDW formation and its sensitivity to disorder.
• The results highlight the potential for quasiparticle bound states in the CDW state of YBa_{2}Cu_{3}O_{y}.
• Further investigation into the nature of defects is warranted to fully understand the reconstructed band structure.