Crystal field excitations in rattling clathrate CeBa$_7$Au$_6$Si$_{40}$
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| Main Authors: | , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866908340538310656 |
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| author | Tagliavini, Michelangelo Mazza, Federico Yan, Xinlin Sidorenko, Andrey Ackermann, Kevin Prokofiev, Andrey Kummer, Kurt Paschen, Silke Haverkort, Maurits W. |
| author_facet | Tagliavini, Michelangelo Mazza, Federico Yan, Xinlin Sidorenko, Andrey Ackermann, Kevin Prokofiev, Andrey Kummer, Kurt Paschen, Silke Haverkort, Maurits W. |
| contents | We investigate the local crystal-field environment of cerium in the clathrate compound CeBa$_7$Au$_6$Si$_{40}$ (Ce-BAS) using resonant inelastic x-ray scattering (RIXS) and magnetic susceptibility measurements. Ce-BAS is a rare example of a system where heavy-fermion physics coexists with low-energy rattling phonon modes, making it a candidate for enhanced thermoelectric performance. Magnetic susceptibility measurements reveal a temperature-dependent local moment that cannot be explained within a static crystal-field model. A fit to the susceptibility data requires strong mixing between the j = 5/2 and j = 7/2 crystal-field states, which implies large internal splittings inconsistent with RIXS spectra. In contrast, RIXS data are well described by a model with negligible j = 5/2 - j = 7/2 mixing and an energy separation of 12 meV between the ground and first excited crystal-field states. The inability to reconcile these two datasets within a static framework points to a dynamical modification of the crystal-field potential. We attribute this to coupling between the Ce 4f electrons and low-energy phonons associated with the Ce rattling motion. This interpretation is consistent with theoretical predictions of phonon-enhanced Kondo effects and dynamical Jahn-Teller distortions. Our results highlight the need for multi-orbital impurity models that include phonon coupling to fully describe the low-energy physics of Ce-BAS. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_19802 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Crystal field excitations in rattling clathrate CeBa$_7$Au$_6$Si$_{40}$ Tagliavini, Michelangelo Mazza, Federico Yan, Xinlin Sidorenko, Andrey Ackermann, Kevin Prokofiev, Andrey Kummer, Kurt Paschen, Silke Haverkort, Maurits W. Strongly Correlated Electrons We investigate the local crystal-field environment of cerium in the clathrate compound CeBa$_7$Au$_6$Si$_{40}$ (Ce-BAS) using resonant inelastic x-ray scattering (RIXS) and magnetic susceptibility measurements. Ce-BAS is a rare example of a system where heavy-fermion physics coexists with low-energy rattling phonon modes, making it a candidate for enhanced thermoelectric performance. Magnetic susceptibility measurements reveal a temperature-dependent local moment that cannot be explained within a static crystal-field model. A fit to the susceptibility data requires strong mixing between the j = 5/2 and j = 7/2 crystal-field states, which implies large internal splittings inconsistent with RIXS spectra. In contrast, RIXS data are well described by a model with negligible j = 5/2 - j = 7/2 mixing and an energy separation of 12 meV between the ground and first excited crystal-field states. The inability to reconcile these two datasets within a static framework points to a dynamical modification of the crystal-field potential. We attribute this to coupling between the Ce 4f electrons and low-energy phonons associated with the Ce rattling motion. This interpretation is consistent with theoretical predictions of phonon-enhanced Kondo effects and dynamical Jahn-Teller distortions. Our results highlight the need for multi-orbital impurity models that include phonon coupling to fully describe the low-energy physics of Ce-BAS. |
| title | Crystal field excitations in rattling clathrate CeBa$_7$Au$_6$Si$_{40}$ |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2504.19802 |