Electronic correlations and spin frustration in the molecular conductors κ -(BEDT-TTF) 2X probed by magnetic quantum oscillations

S. Erkenov, S. Fust, S. Oberbauer, W. Biberacher, N. D. Kushch, H. Müller, F. L. Pratt, R. Gross, M. V. Kartsovnik

Research output: Contribution to journalArticlepeer-review

Abstract

The layered molecular conductors κ-(BEDT-TTF)2X 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. To elucidate this issue, we study, in a broad pressure range, magnetic quantum oscillations in two κ salts, the ambient-pressure antiferromagnetic insulator with X=Cu[N(CN)2]Cl and the ambient-pressure superconductor with X=Cu(NCS)2. The data obtained provide quantitative information on important parameters governing the Mott physics, including the electronic correlation strength ratio U/t and the spin frustration ratio t′/t. This allows us to directly evaluate the effects of physical and chemical pressure in the present materials. Our analysis reveals significant weakening of both the electronic correlation strength and the magnetic ordering instability under pressure. On the other hand, the anion replacement is found to considerably change the frustration parameter t′/t while leaving the correlation strength virtually unaffected.

Original languageEnglish
Article number205149
JournalPhysical Review B
Volume110
Issue number20
DOIs
StatePublished - 15 Nov 2024

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