High-brilliance synchrotron radiation sources have opened new avenues for x-ray polarization analysis that go far beyond conventional polarimetry in the optical domain. With linear x-ray polarizers in a crossed setting, polarization extinction ratios down to ${{10}^{- 10}}$ can be achieved. This renders the method sensitive to probe the tiniest optical anisotropies that would occur, for example, in strong-field quantum electrodynamics due to vacuum birefringence and dichroism. Here we show that high-purity polarimetry can be employed to reveal electronic anisotropies in condensed matter systems with utmost sensitivity and spectral resolution. Taking CuO and ${{\rm La}_2}{{\rm CuO}_4}$ as benchmark systems, we present a full characterization of the polarization changes across the Cu K-absorption edge and their separation into dichroic and birefringent contributions. At diffraction-limited synchrotron radiation sources and x-ray lasers, where polarization extinction ratios of ${{10}^{- 12}}$ can be achieved, our method has the potential to assess birefringence and dichroism of the quantum vacuum in extreme electromagnetic fields.

中文翻译：

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通过高纯度偏光法解散X射线二色性和双折射

高亮度同步加速器辐射源为x射线偏振分析开辟了新途径，远远超出了光学领域的常规偏振法。使用在交叉设置中的线性X射线偏振器，可以实现低至$ {{10} ^ {-10}} $的偏振消光比。这使得该方法对探测最小的光学各向异性很敏感，例如在由于真空双折射和二色性导致的强场量子电动力学中会出现这种微小的光学各向异性。在这里，我们表明可以使用高纯度极化仪以最大的灵敏度和光谱分辨率揭示凝聚态系统中的电子各向异性。取CuO和$ {{\ rm La} _2} {{\ rm CuO} _4} $作为基准系统，我们全面描述了整个Cu K吸收边缘的偏振变化及其分离为二色性和双折射性的特征。在衍射受限的同步加速器辐射源和X射线激光器中，可以达到$ {{{10} ^ {-12}} $的偏振消光比，我们的方法有可能在极端情况下评估量子真空的双折射和二色性。电磁场。