利用光阱不对称顶分子探测P、T对称性破缺
Probing $P,T$-Symmetry Violation with Optically Trapped Asymmetric Top Molecules
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中文总结 AI 辅助
本研究以类碱土金属单酰胺等不对称顶分子为对象，通过从头计算与有效哈密顿量建模，识别出工程化时钟跃迁和魔术阱条件，可实现远超当前极限的电子电偶极矩灵敏度，为对称性破缺测量提供了可调平台。
中文摘要 AI 辅助
对P、T对称性破缺电磁矩的搜寻是超出标准模型物理最灵敏的探针之一。突破现有极限将得益于在低电场下具有完全可控取向、长相干时间和可激光冷却的分子——不对称顶分子（ATM）。利用ATM中固有的转动K双重态以及由C2v对称性和核自旋统计所带来的长寿命（T1≳10秒）宇称双重态，这类物种在适度实验室场中兼具大电极化率和长相干时间。我们研究类碱土金属单酰胺M-NH2（M=Ca、Sr、Ba、Yb、Ra），其具有适合激光冷却的电子结构。我们对精细和超精细常数进行从头计算，明确相对论效应在自旋-转动张量中的重要性。随后，有效哈密顿量对振转基态的转动和超精细结构进行建模，量化电子电偶极矩（EDM）灵敏度并确定可行的测量方案。我们计算外场的影响，识别出可抑制对外场扰动的灵敏度同时保留强EDM灵敏度的工程化时钟跃迁，并表征光阱中消除差分光移的魔术阱条件。在这些条件下，我们预计统计电子EDM灵敏度将比当前最佳实验极限高出一个数量级以上，且通过增加分子数和相干时间可进一步提升。我们的结果确立了不对称顶分子作为具有长相干时间的可调平台，用于灵敏的对称性破缺测量。
英文摘要
Searches for $P,T$-violating electromagnetic moments are among the most sensitive probes of physics beyond the Standard Model. Extending beyond current limits will benefit from molecules with fully controllable orientation at low electric fields, long coherence times, and laser coolability---all offered by asymmetric top molecules (ATMs). Exploiting the intrinsic rotational $K$-doubling in ATMs and the associated long-lived ($T_1 \gtrsim 10$ s) parity doublets afforded by $C_{2v}$ symmetry and nuclear-spin statistics, these species combine large electric polarizability with long coherence times in modest laboratory fields. We study alkaline-earth(-like) monoamides, $\mathcal{M}$--NH$_2$ ($\mathcal{M}$ = Ca, Sr, Ba, Yb, Ra), which possess favorable electronic structure for laser cooling. We perform \textit{ab initio} calculations of fine and hyperfine constants, identifying the importance of relativistic effects in the spin-rotation tensor. An effective Hamiltonian then models the rotational and hyperfine structure of the vibronic ground state, quantifying electron electric dipole moment (EDM) sensitivities and identifying feasible measurement schemes. We compute the effect of external fields and identify engineered clock transitions that suppress sensitivity to external perturbations while retaining strong EDM sensitivity, and characterize the magic trapping conditions that null differential light shifts in an optical trap. Under these conditions we project a statistical electron-EDM sensitivity over an order of magnitude beyond current best experimental limits, with further gains available from increased molecule number and coherence time. Our results establish asymmetric top molecules as a tunable platform for sensitive symmetry-violation measurements with long coherence times.
