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Symmetry-Controlled Thermal Activation in Pyramidal Coulomb Clusters: Testing Kramers-Langer Theory
Akhil Ayyadevara1, Anand Prakash1, Shovan Dutta1
1Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560080, India.
Physical Review Letters
|July 26, 2026
Summary
We demonstrate how symmetry controls the collective dynamics of laser-cooled ions in a Paul trap. Breaking symmetry suppresses low-barrier inversions, analogous to molecular kinetic isotope effects.
Area of Science:
- Atomic, Molecular, and Optical Physics
- Condensed Matter Physics
- Quantum Information Science
Background:
- Laser-cooled ions in electromagnetic traps form tunable mesoscopic systems.
- Collective dynamics arise from trapping potentials, Coulomb interactions, and laser scattering.
- These systems offer insights into fundamental physics and quantum technologies.
Purpose of the Study:
- To engineer and investigate thermally activated switching between ion configurations.
- To explore the role of symmetry in controlling collective dynamics.
- To establish trapped ions as a platform for studying symmetry-controlled phenomena.
Main Methods:
- Confining five laser-cooled calcium ions (Ca+) in a Paul trap.
- Inducing structural inversions via thermal activation.
- Utilizing multidimensional Kramers-Langer theory for rate analysis.
- Comparing experimental results with Langevin dynamics simulations.
Main Results:
- Identical ions (40Ca+) exhibited inversions via Berry pseudorotation, enabled by permutation symmetry.
- Accurate thermometry of the ion cluster at 1.86±0.03 mK was achieved.
- Substituting the apex ion with a heavier isotope (44Ca+) broke symmetry and suppressed inversions.
- Symmetry breaking shifted inversion pathways to higher energy barriers.
Conclusions:
- Thermally activated switching in trapped ions is sensitive to symmetry.
- Trapped ions serve as a structural analog for molecular kinetic isotope effects.
- This work highlights the potential of ion traps for exploring symmetry-controlled dynamics.
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