2024/06/27 by Oles Matsyshyn, Ying Xiong, Matsyshyn, Oles +3 · 1 citation
Physics and Astronomy · #FOS: Physical sciences #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Quantum Mechanics and Non-Hermitian Physics #Quantum Physics (quant-ph)
paper · pdf · doi:10.48550/arxiv.2406.19444
openalex publication_date 2024/06/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Superpositions between states in doubly degenerate Kramers pairs can act as an internal degree of freedom. Here we uncover a Kramers dichroism in PT symmetric magnets: interband transitions induced by circularly polarized light irradiation produce a coherent superposition between Kramers partnered states. This allows to optically control the Kramers degree of freedom. In contrast, Kramers pairs optically excited by linearly polarized light remain in a completely mixed state. Strikingly, we find a class of second-order nonlinear responses that directly track the coherence between Kramers partnered states. Such Kramers nonlinearities can be pronounced producing large second-order nonlinear layer polarization responses activated by Kramers degeneracy in layered antiferromagnets. Together with Kramers dichroism, these render optical responses a novel means for accessing the Kramers degree of freedom and diagnosing their quantum coherent state.