Electronic correlations and spin frustration in the molecular conductors $\kappa$-(BEDT-TTF)$_2$X probed by magnetic quantum oscillations
The layered molecular conductors $\kappa$-(BEDT-TTF)$_2$X are a perfect experimental platform for studying the physics of the Mott transition and related exotic electronic states. In these materials, the subtle balance between various instabilities of the normal metallic state can be efficiently cha...
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Main Authors | , , , , , , , , |
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Format | Journal Article |
Language | English |
Published |
04.09.2024
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Subjects | |
Online Access | Get full text |
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Summary: | The layered molecular conductors $\kappa$-(BEDT-TTF)$_2$X are a perfect
experimental platform for studying the physics of the Mott transition and
related exotic electronic states. In these materials, the subtle balance
between various instabilities of the normal metallic state can be efficiently
changed by applying a very moderate external pressure or by subtle chemical
modifications, e.g. by a replacement of the insulating anion X$^{-}$,
frequently referred to as ``chemical pressure''. A crucially important but
still unsettled issue is an exact understanding of the influence of physical
and chemical pressure on the electronic structure. Here, we use magnetic
quantum oscillations to explore in a broad pressure range the behavior of the
key parameters governing the Mott physics, the electronic correlation strength
ratio $U/t$ and the spin frustration ratio $t'/t$ in two $\kappa$ salts, the
ambient-pressure antiferromagnetic insulator with X = Cu[N(CN)$_2$]Cl and the
ambient-pressure superconductor with X = Cu(NCS)$_2$. Our analysis shows that
pressure effectively changes not only the conduction bandwidth but also the
degree of spin frustration, thus weakening both the electronic correlation
strength and the magnetic ordering instability. At the same time, we find that
the replacement of the anion Cu[N(CN)$_2$]Cl$^-$ by Cu(NCS)$_2^-$ results in a
significant increase of the frustration parameter $t'/t$, leaving the
correlation strength essentially unchanged. |
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DOI: | 10.48550/arxiv.2409.02799 |