Xatu: eXcitons from ATomistic calcUlations

Xatu is a computational package and library for solving the Bethe-Salpeter Equation (BSE) in condensed matter systems. It allows efficient and flexible exciton calculations starting from electronic structures obtained via tight-binding or DFT using localized orbitals.

The BSE is constructed from user-defined input and then diagonalized to obtain the excitonic spectrum. The results can be post-processed to extract physical properties such as optical absorption and exciton localization.

Note

📄 Reference Paper: Efficient computation of optical excitations in two-dimensional materials with the Xatu code, Computer Physics Communications, 2024

Documentation Contents

Getting Started

• Installation Guide
• Input File Descriptions
• Command-Line Usage

Outputs

• .eigval — Exciton Energies
• .states — Exciton Eigenstates
• .kwf — Momentum-Space Probability Density
• .rswf — Real-Space Probability Density
• Conductivity Outputs (.dat files)
• Exciton Oscillator Strengths (_osc.dat)
• .spin — Exciton Spin Projection
• Spin Projection Output

Theory and Methods

• Screening Potentials in Xatu
• Bethe-Salpeter Equation in Xatu
• Optical Conductivity from Excitonic States

Miscellaneous & Devs

• Citing Xatu
• License
• Developer and API Guide