Recent experiments on 2H-TaSe(2) contradict the long-held view of the charge density wave arising from a nested band structure. An intrinsically strong coupling view, involving a charge density wave state arising as a Bose condensation of preformed excitons emerges as an attractive, albeit scantily investigated alternative. Using the local density approximation plus multiorbital dynamic mean field theory, we show that this scenario agrees with a variety of normal state data for 2H-TaSe(2). Based thereupon, the ordered states in a subset of dichalcogenides should be viewed as instabilities of a correlated, preformed excitonic liquid.

Traditional routes to Charge-Density-Wave in transition metal dichalcogenides, relying on Fermi surface nesting or Jahn-Teller instabilities have recently been brought into question. While this calls for exploration of alternative views, paucity of theoretical guidance sustains lively controversy on the origin of, and interplay between CDW and superconductive orders in transition metal dichalcogenides. Here, we explore a preformed excitonic liquid route, heavily supplemented by modern correlated electronic structure calculations, to an excitonic-CDW order in 1T-TiSe 2 . We show that orbital-selective dynamical localisation arising from preformed excitonic liquid correlations is somewhat reminiscent to states proposed for d-and f -band quantum criticality at the border of magnetism. Excellent quantitative explication of a wide range of spectral and transport responses in both normal and CDW phases provides strong support for our scenario, and suggests that soft excitonic liquid fluctuations mediate superconductivity in a broad class of transition metal dichalcogenides on the border of CDW. This brings the transition metal dichalcogenides closer to the bad actors in d-and f -band systems, where anomalously soft fluctuations of electronic origin are believed to mediate unconventional superconductivity on the border of magnetism.

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Biocompatible quantum dots (QDs) have attracted a lot of attention due to potential biological applications (drug delivery, sensing and diagnosis). Here, we have synthesized 2-4 nm size biocompatible ZnS QDs...

Charge density wave (CDW) states in solids bear an intimate connection to underlying fermiology. Thus, modification of the latter by suitable perturbations provides an attractive handle to unearth novel CDW states. Here, we combine extensive magnetotransport experiments and first-principles correlated electronic structure calculations on non-magnetic tritelluride LaTe3 to uncover phenomena rare in CDW systems: (i) highly anisotropic large transverse magnetoresistance (MR) upon rotation of magnetic field about current parallel to crystallographic c-axis, (ii) anomalously large positive MR with spike-like peaks at characteristic angles when the angle between current and field is varied in the bc-plane, (iii) extreme sensitivity of the angular variation of MR on field and temperature. These novel observations find a comprehensive explication in theoretical picture that captures field-induced electronic structure modification in LaTe3. We underline a unique possibility of a second, field-induced CDW from the field-reconstructed Fermi surface.