Spinfinity

Python package for simulating quantum spin systems in tunnel junction experiments.

Available at: GitHub - WillkeLab/Spinfinity

Intended Use

Spinfinity is intended for researchers working on quantum spin systems in scanning probe microscopy. The package is designed for modeling spin structures in double-barrier tunnel junctions, solving their spin Hamiltonians, and simulating observables that can be compared to experimental spectroscopy data.

Typical use cases include:

• modeling single-spin and multi-spin systems
• calculating eigenenergies and eigenstates of custom spin Hamiltonians
• simulating tunneling-induced transition rates and steady-state populations
• computing differential conductance spectra for comparison with experiment
• computing Electron Spin Resonance spectra and related driven dynamics
• simulating the time evolution of spin systems in the tunneling junction
• simulating pulsed ESR experiments such as Rabi oscillations

Getting started

Read the User guide for the code structure and typical workflows. Follow the tutorials for worked examples.

References

• Ternes, M., Spin excitations and correlations in scanning tunneling spectroscopy. New J. Phys. 17, 063016 (2015). https://dx.doi.org/10.1088/1367-2630/17/6/063016
• Loth, S., von Bergmann, K., Ternes, M. et al. Controlling the state of quantum spins with electric currents. Nature Phys 6, 340–344 (2010). https://doi.org/10.1038/nphys1616
• Yang, K., Willke, P., Bae, Y. et al. Electrically controlled nuclear polarization of individual atoms. Nature Nanotech 13, 1120–1125 (2018). https://doi.org/10.1038/s41565-018-0296-7
• Yang, K., Phark, SH., Bae, Y. et al. Probing resonating valence bond states in artificial quantum magnets. Nat Commun 12, 993 (2021). https://doi.org/10.1038/s41467-021-21274-5

Citation

If you use Spinfinity in scientific work, please cite the software together with the relevant methodological references listed above.

Suggested citation text:

@software{Spinfinity,
  title   = {Spinfinity: A Python package for simulating quantum spin systems in tunnel junction experiments},
  author  = {Greule, Paul and Arnold, Jonas and Renz, Luise and Hardeweg, Lovis and Matusche, Johanna and Huang, Wantong and Au-Yeung, Kwan Ho and Ascheraden, Hannah and Schwenk, Johannes and Willke, Philip},
  year    = {2026},
  url     = {https://github.com/WillkeLab/Spinfinity}
}

Support

For support please contact: paul.greule@kit.edu

Contributing

We welcome everyone to contribute to this project. Please contact: paul.greule@kit.edu

License

Spinfinity is licensed under the GNU General Public License (GPL). See the repository for the full license text.