Calculations of time-reversal symmetry-violating sensitivity parameters in a relativistic exact two-component coupled-cluster framework

Precision spectroscopy searches of new physics beyond the Standard Model probe time-reversal symmetry in atoms and molecules. The measured energy-splitting is proportional to the atomic or molecular sensitivity parameters. These parameters are inherently electronic-structure properties and are enhanced by relativistic effects. Therefore, precision measurements typically use heavy atoms or molecules containing heavy atoms. Accurate calculations of these parameters in molecules containing heavy atoms require accurate treatments of relativistic effects.



In this presentation, we presented relativistic exact two-component coupled-cluster framework with analytic energy gradients for efficient and accurate calculations of time-reversal symmetry-violating sensitivity parameters in molecules containing heavy atoms. By exploiting analytic relativistic coupled-cluster gradient techniques, the new computational tool offers at least an order of magnitude improvement in efficiency compared to the previous state of the art techniques based on numerical differentiation of energies. This will greatly facilitate the identification of candidate molecules of interest to precision spectroscopy searches of new physics beyond the Standard Model.