Electronic correlations and spin frustration in the molecular conductors $\kappa$-(BEDT-TTF)${}_2$X probed by magnetic quantum oscillations

Abstract

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 $t^{\prime }/t$ 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 $t^{\prime }/t$, leaving the correlation strength essentially unchanged.

13 pages,including 7 Figures. Supplemental Material is available upon request

References in corpus (15)

• Quantum frustration in organic Mott insulators: from spin liquids to unconventional superconductors
• Strong electronic correlations in superconducting organic charge transfer salts
• Quantum Oscillations in Hole-Doped Cuprates
• Finite temperature Mott transition in Hubbard model on anisotropic triangular lattice
• Superconductivity and a Mott Transition in a Hubbard Model on an Anisotropic Triangular Lattice
• Gapped magnetic ground state in quantum-spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$-Cu${}_2$(CN)${}_3$
• Mott Transition in a Valence Bond Solid Insulator with a Triangular Lattice
• Importance of Spin-Orbit Coupling in Organic BEDT-TTF and BEDT-TSF Salts
• Quasi-2D Fermi surface in the anomalous superconductor UTe2
• Mott transition and magnetism of the triangular-lattice Hubbard model with next-nearest-neighbor hopping
• Boson-assisted tunneling in layered metals
• Spin Vortex Crystal Order in Organic Triangular Lattice Compound
• Coherent heavy charge carriers in an organic conductor near the bandwidth-controlled Mott transition
• Truncated mass divergence in a Mott metal
• Anomalously field-susceptible spin soft-matter emerging in an electric-dipole liquid candidate