Fermi surface of 3d1 perovskite CaVO3 near the Mott transition

Hidden transport phenomena in an ultraclean correlated metal

Advancements in materials synthesis have been key to unveil the quantum nature of electronic properties in solids by providing experimental reference points for a correct theoretical description. Here, we report hidden transport phenomena emerging in the ultraclean limit of the archetypical correlated electron system SrVO3. The low temperature, low magnetic field transport was found to be dominated by anisotropic scattering, whereas, at high temperature, we find a yet undiscovered phase that exhibits clear deviations from the expected Landau Fermi liquid, which is reminiscent of strange-metal physics in materials on the verge of a Mott transition. Further, the high sample purity enabled accessing the high magnetic field transport regime at low temperature, which revealed an anomalously high Hall coefficient. Taken with the strong anisotropic scattering, this presents a more complex picture of SrVO3 that deviates from a simple Landau Fermi liquid. These hidden transport anomalies observed in the ultraclean limit prompt a theoretical reexamination of this canonical correlated electron system beyond the Landau Fermi liquid paradigm, and more generally serves as an experimental basis to refine theoretical methods to capture such nontrivial experimental consequences emerging in correlated electron systems.

The Influence of Oxygen Activity on Phase Composition, Crystal Structure, and Electrical Conductivity of CaV1–xMoxO3±δ

Perovskite–like vanadate–molybdates are interesting from the point of view of their metal–like conductivity, which combines the correlated and free electron nature. A series of CaV1–xMoxO3–δ solid solutions was considered near the Mo concentration x = 0.4, where a difficult–to–perceive structural transition was previously detected. High-resolution transmission electron microscopy revealed the phase separation of CaV0.6Mo0.4O3–δ into nanoscale regions with different ratios of V and Mo concentrations, despite X–ray diffraction analysis exhibiting a homogeneous perovskite structure. The rest of the compositions from the CaV1–xMoxO3–δ series do not show phase separation. The nonmonotonic behavior of the conductivity and linear expansion of CaV1–xMoxO3±δ was shown when the oxygen activity in the N2-H2-H2O gas mixture was varied, which is mainly determined by the partial decomposition of the perovskite phase. Against this background, the behavior of the electrical properties of the CaV1–xMoxO3±δ individual phase remains unclear.

K2CaV2O7: a pyrovanadate with a new layered type of structure in the A2BV2O7 family

The crystal structure of K(2)CaV(2)O(7) prepared by a conventional solid-state reaction has been solved by a direct method and refined using Rietveld full profile fitting based on X-ray powder diffraction data. This compound crystallises in the triclinic space group (P1, Z = 2) with unit cell constants a = 7.1577(1) Å, b = 10.5104(2) Å, c = 5.8187(1) Å, α = 106.3368(9)°, β = 106.235(1)°, γ = 71.1375(9)°. The structure can be described as infinite undulating CaV(2)O(7)(2-) layers parallel to the ac plane, which consist of pairs of edge-sharing CaO(6) octahedra connected to each other through V(2)O(7) pyrogroups. The potassium atoms are positioned in two sites between the layers, with a distorted IX-fold coordination of oxygen atoms. The chemical composition obtained from the structural solution was confirmed by energy-dispersive X-ray analysis. The stability of compounds in the family of alkali metal calcium pyrovanadates is discussed based on an analysis of the correlation between anion and cation sizes and theoretical first-principles calculations.

Direct observation of the mass renormalization in SrVO3 by angle resolved photoemission spectroscopy

Band dispersions and Fermi surfaces of the three-dimensional Mott-Hubbard system SrVO3 are directly observed by angle-resolved photoemission spectroscopy. An observed spectral weight distribution near the Fermi level (E(F)) shows cylindrical Fermi surfaces as predicted by band-structure calculations. By comparing the experimental results with calculated surface electronic structures, we conclude that the obtained band dispersion reflects the bulk electronic structure. The enhanced effective electron mass obtained from the energy band near E(F) is consistent with the bulk thermodynamic properties and hence with the normal Fermi-liquid behavior of SrVO3.

Mutual experimental and theoretical validation of bulk photoemission spectra of Sr1-xCaxVO3

We report high-resolution high-energy photoemission spectra together with parameter-free LDA + DMFT (local density approximation + dynamical mean-field theory) results for Sr1-xCaxVO3, a prototype 3d(1) system. In contrast to earlier investigations the bulk spectra are found to be insensitive to x. The good agreement between experiment and theory confirms the bulk sensitivity of the high-energy photoemission spectra.

de Haas-van Alphen effect across the metamagnetic transition in Sr3Ru2O7

We report a study of the de Haas-van Alphen (dHvA) effect on the itinerant metamagnet Sr3Ru2O7. Extremely high sample purity allows the observation of dHvA oscillations both above and below the metamagnetic transition field of 7.9 T. The quasiparticle masses are fairly large away from the transition, and are enhanced by up to an extra factor of 3 as the transition is approached, but the Fermi surface topography change is quite small. The results are qualitatively consistent with a field-induced Stoner transition in which the mass enhancement is the result of critical fluctuations.

Surface versus bulk Coulomb correlations in photoemission spectra of SrVO3 and CaVO3

Recent photoemission spectra of the perovskite series CaxSr1-xVO3 revealed strong modifications associated with surface contributions. To study the effect of Coulomb correlations in the bulk and at the surface, the quasiparticle spectra are evaluated using the dynamical mean field theory. It is shown that as a result of the reduced coordination number of surface atoms correlation effects are stronger at the surface than in the bulk, in agreement with experiment.