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arXiv · 2406.19444

Kramers Dichroism in PT Symmetric Magnets

Oles Matsyshyn·Ying Xiong·Justin C. W. Song
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Abstract

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.

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Oles Matsyshyn, Ying Xiong, Justin C. W. Song. 2024-06-27. Kramers Dichroism in PT Symmetric Magnets. https://arxiv.org/abs/2406.19444

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