Electronic structure of pyrochlore Cd(2)Re(2)O(7).

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Materials Science

Background:

• Cd2Re2O7 exhibits distinct high-, middle-, and low-temperature phases.
• Understanding the electronic band structure is crucial for predicting material properties.

Purpose of the Study:

• To perform detailed band structure calculations for Cd2Re2O7 in its different temperature phases.
• To investigate the effects of spin-orbit interaction and on-site Coulomb repulsion (U) on electronic properties.
• To correlate calculated electronic structures with experimental observations like X-ray absorption spectroscopy and Hall coefficient measurements.

Main Methods:

• Density Functional Theory (DFT) calculations using the generalized gradient approximation (GGA) and GGA plus Hubbard U (GGA+U) methods.
• Incorporation of spin-orbit interaction self-consistently.
• Analysis of band structures, Fermi surfaces, and carrier numbers.

Main Results:

• On-site U has minimal impact on Re 5d band structures, aligning well with X-ray absorption spectroscopy (XAS) data.
• GGA+U calculations accurately reproduce Cd 4d band energies, suggesting localized Cd 4d electrons.
• Spin-orbit coupling induces spin and orbital magnetic moments in the middle-temperature phase.
• The low-temperature phase unexpectedly displays quasi-two-dimensional Fermi surfaces.
• Calculated carrier numbers are qualitatively consistent with experimental Hall coefficient measurements.

Conclusions:

• Cd 5d electrons are localized, while Re 5d electrons are relatively itinerant.
• The low-temperature phase of Cd2Re2O7 possesses unique quasi-two-dimensional electronic characteristics.
• The theoretical calculations provide a strong basis for understanding the experimental properties of Cd2Re2O7 across its temperature phases.