Tuning Incommensurate Charge Order in Ba$_{1-x}$Sr$_x$Al$_4$ and Ba$_{1-y}$Eu$_y$Al$_4$
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arXiv
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| Natura: | Preprint |
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2025
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| author | Saraf, Prathum Clements, Eleanor M. Sokratov, Danila Saha, Shanta Zavalij, Peter Heitmann, Thomas W. Lynn, Jeffrey W. Bernal-Choban, Camille Chaudhuri, Dipanjan Kengle, Caitlin Su, Yue Bettler, Simon Manning, Nathan Abbamonte, Peter Biswas, Sananda Valentí, Roser Paglione, Johnpierre |
| author_facet | Saraf, Prathum Clements, Eleanor M. Sokratov, Danila Saha, Shanta Zavalij, Peter Heitmann, Thomas W. Lynn, Jeffrey W. Bernal-Choban, Camille Chaudhuri, Dipanjan Kengle, Caitlin Su, Yue Bettler, Simon Manning, Nathan Abbamonte, Peter Biswas, Sananda Valentí, Roser Paglione, Johnpierre |
| contents | The BaAl$_4$-type structure family is home to a vast landscape of interesting and exotic properties, with descendant crystal structures hosting a variety of electronic ground states including magnetic, superconducting and strongly correlated electron phenomena. BaAl$_4$ itself hosts a non-trivial topological band structure, but is otherwise a paramagnetic metal. However, the other members of the $A$Al$_4$ family ($A$= alkali earth), including SrAl$_4$ and EuAl$_4$, exhibit symmetry-breaking ground states including charge density wave (CDW) and magnetic orders. Here we investigate the properties of the solid solution series Ba$_{1-x}$Sr$_x$Al$_4$ and Ba$_{1-y}$Eu$_y$Al$_4$ using transport, thermodynamic and scattering experiments to study the evolution of the charge-ordered state as it is suppressed with Ba substitution to zero near 50% substitution in both systems. Neutron and x-ray diffraction measurements reveal an incommensurate CDW state in SrAl$_4$ with $c$-axis-oriented ordering vector (0, 0, 0.097) that evolves with Ba substitution toward a shorter wavelength. A similar progression is observed in the Ba$_{1-y}$Eu$_y$Al$_4$ series that also scales with the ordering temperature, revealing a universal correlation between charge-order transition temperature and ordering vector that points to a critical wavevector that stabilizes CDW order in both systems. We study the evolution of the phonon band structure in the Ba$_{1-x}$Sr$_x$Al$_4$ system, revealing the suppression of the CDW phase matches the suppression of a phonon instability at precisely the same momentum as observed in experiments, confirming the electron-phonon origin of charge order in this system. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_02140 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Tuning Incommensurate Charge Order in Ba$_{1-x}$Sr$_x$Al$_4$ and Ba$_{1-y}$Eu$_y$Al$_4$ Saraf, Prathum Clements, Eleanor M. Sokratov, Danila Saha, Shanta Zavalij, Peter Heitmann, Thomas W. Lynn, Jeffrey W. Bernal-Choban, Camille Chaudhuri, Dipanjan Kengle, Caitlin Su, Yue Bettler, Simon Manning, Nathan Abbamonte, Peter Biswas, Sananda Valentí, Roser Paglione, Johnpierre Strongly Correlated Electrons The BaAl$_4$-type structure family is home to a vast landscape of interesting and exotic properties, with descendant crystal structures hosting a variety of electronic ground states including magnetic, superconducting and strongly correlated electron phenomena. BaAl$_4$ itself hosts a non-trivial topological band structure, but is otherwise a paramagnetic metal. However, the other members of the $A$Al$_4$ family ($A$= alkali earth), including SrAl$_4$ and EuAl$_4$, exhibit symmetry-breaking ground states including charge density wave (CDW) and magnetic orders. Here we investigate the properties of the solid solution series Ba$_{1-x}$Sr$_x$Al$_4$ and Ba$_{1-y}$Eu$_y$Al$_4$ using transport, thermodynamic and scattering experiments to study the evolution of the charge-ordered state as it is suppressed with Ba substitution to zero near 50% substitution in both systems. Neutron and x-ray diffraction measurements reveal an incommensurate CDW state in SrAl$_4$ with $c$-axis-oriented ordering vector (0, 0, 0.097) that evolves with Ba substitution toward a shorter wavelength. A similar progression is observed in the Ba$_{1-y}$Eu$_y$Al$_4$ series that also scales with the ordering temperature, revealing a universal correlation between charge-order transition temperature and ordering vector that points to a critical wavevector that stabilizes CDW order in both systems. We study the evolution of the phonon band structure in the Ba$_{1-x}$Sr$_x$Al$_4$ system, revealing the suppression of the CDW phase matches the suppression of a phonon instability at precisely the same momentum as observed in experiments, confirming the electron-phonon origin of charge order in this system. |
| title | Tuning Incommensurate Charge Order in Ba$_{1-x}$Sr$_x$Al$_4$ and Ba$_{1-y}$Eu$_y$Al$_4$ |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2507.02140 |