Spin and charge are inseparable traits of an electron, but in one-dimensional solids, theory predicts their separation into collective modes—as independent excitation quanta (or particles) called spinons and holons. Experimentalists have long sought to verify this effect. Angle-resolved photoemission (ARPES) should provide the most direct evidence of spin–charge separation, as the single quasiparticle peak splits into a spinon–holon two-peak-like structure. Despite extensive ARPES experiments, the unambiguous observation of the two-peak structure has remained elusive. Here we report ARPES data from SrCuO2, made possible by recent technological developments, that unequivocally show the spinon–holon two-peak structure and their distinct dispersions. The spinon and holon branches are found to have energy scales of ∼0.43 and 1.3 eV, respectively, which are in quantitative agreement with the theoretical predictions.
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This work is supported (in part) by the Korea Science and Engineering Foundation through the Center for Strongly Correlated Materials Research. Z.-X.S. acknowledges support from DOE contract DE-FG03-01ER45929-A001. ALS is operated by the DOE's Office of BES, Division of Materials Science, under Contract No. DE-AC03-76SF00098.
The authors declare no competing financial interests.
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Kim, B., Koh, H., Rotenberg, E. et al. Distinct spinon and holon dispersions in photoemission spectral functions from one-dimensional SrCuO2. Nature Phys 2, 397–401 (2006). https://doi.org/10.1038/nphys316
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