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

From soft polymeric gels to hardened cement paste, amorphous solids under constant load exhibit a pronounced time-dependent deformation called creep. The microscopic mechanism of such a phenomenon is poorly understood in amorphous materials and constitutes an even greater challenge in densely packed and chemically reactive granular systems. Both features are prominently present in hydrating cement pastes composed of calcium silicate hydrate (C-S-H) nanoparticles, whose packing density increases as a function of time, while cement hydration is taking place. Performing nano-indentation tests and porosity measurements on a large collection of samples at various stages of hydration, we show that the creep response of hydrating cement paste is mainly controlled by the inter-particle distance and results from slippage between (C-S-H) nanoparticles. Our findings provide a unique insight into the microscopic mechanism underpinning the creep response in aging granular materials, thus paving the way for the design of concrete with improved creep resistance., Comment: 14 pages, 8 figures

In spite of extensive experimental studies of the angular dependent magnetoresistance (ADMR) of the low temperature phase (LTP) of alpha-(BEDT-TTF)_2KHg(SCN)_4 about a decade ago, the nature of LTP remains elusive. Here we present a new study of ADMR of LTP in alpha-(ET)_2 salts assuming that LTP is unconventional charge density wave (UCDW). In the presence of magnetic field the quasiparticle spectrum in UCDW is quantized, which gives rise to striking ADMR in UCDW. The present model appears to account for many existing ADMR data of alpha-(BEDT-TTF)_2KHg(SCN)_4 remarkably well., Comment: 6 pages, 4 figures