A new limit on the electron’s electric dipole moment

Physicists have been able to describe our entire universe using just two mathematical models:
General Relativity, for gravity, and the Standard Model, for everything else. While the
Standard Model has been tested to exquisite precision and is generally successful, it has some
serious inconsistencies: it fails, for example, to explain why matter dominates over antimatter in
our universe. New models aiming to eliminate these inconsistencies often introduce additional
symmetry violation, which in turn results in symmetry-violating properties in fundamental particles
like electrons. In particular, many new physics theories predict that the electron will have a
non-zero electric dipole moment (EDM) aligned with the spin axis, which violates time-reversal
symmetry. Placing limits on the magnitude of the electron EDM directly constrains new physics
theories at energies beyond the reach of the Large Hadron Collider. Here we present a new
experimental limit on the electron’s electric dipole moment using trapped HfF⁺ in rotating bias
fields: |de| < 4.4 × 10⁻³⁰ e·cm. Our measurement is a factor of 2.5 better than the previous best
limit.