A remarkable match of optical response in the amorphous-crystalline and zinc blende-rock salt phase pairs of GeTe.

Despite a large amount of theoretical and experimental work performed so far, the search of phase change materials (PCMs) is done with use of numerical modeling. However, it is not fully clear how and why the phase change translates into the optical contrast. In this work, we argue that a key prerequisite for a material to have a pronounced difference in optical properties between crystalline and glassy phases of PCM is the similar contrast between the observed crystalline and (may be experimentally inaccessible) parent crystalline polymorph of the glassy phase.

Solid-state quantum chemistry with ΘΦ (ThetaPhi): Spin-liquids, superconductors, and magnetic superstructures made computationally available.

We present a standalone ΘΦ (ThetaPhi) package capable to read the results of ab initio DFT/PAW quantum-chemical solid-state calculations processed through various tools projecting them to the atomic basis states as an input and to perform on top of this an analysis of so derived electronic structure which includes (among other options) the possibility to obtain a superconducting (Bardeen-Cooper-Schrieffer, BCS), spin-liquid (resonating valence bond, RVB) states/phases as solutions of the electronic structure problem along with the magnetically ordered phases with an arbitrary pitch (magnetic superstructure) vector. Remarkably, different solutions of electronic-structure problems come out as temperature-dependent (exemplified by various superconducting and spin-liquid phases) which feature is as well implemented. All that is exemplified by model calculations on 1D chain, 2D square lattice as well as on more realistic superconducting doped graphene, magnetic phases of iron, and spin-liquid and magnetically ordered states of a simplest nitrogen-based copper pseudo-oxide, CuNCN, resembling socalled metal-oxide framework (MOF) phases by the atomic interlinkage.

Robustness of Rashba and Dirac Fermions against Strong Disorder.

By addressing the interplay between substitutional disorder and spin-orbit-coupling in chalcogenide alloys, we predict a strong robustness of spectral features at the Fermi energy. Indeed, supplementing our state of the art first-principles calculations with modeling analysis, we show that the disorder self-energy is vanishingly small close to the band gap, thus i) allowing for bulk Rashba-like spin splitting to be observed in ferroelectric alloys by means of Angle Resolved PhotoEmission Spectroscopy, and ii) protecting the band-character inversion related to the topological transition in recently discovered Topological Crystalline Insulators. Such a protection against strong disorder, which we demonstrate to be general for three dimensional Dirac systems, has potential and valuable implications for novel technologies, as spintronics and/or spinorbitronics.

Electric control of magnetism at the Fe/BaTiO₃ interface.

Interfacial magnetoelectric coupling is a viable path to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO₃ system, only tiny changes of the interfacial Fe magnetic moment upon reversal of the BaTiO₃ dielectric polarization have been predicted so far. Here, by using X-ray magnetic circular dichroism in combination with high-resolution electron microscopy and first principles calculations, we report on an undisclosed physical mechanism for interfacial magnetoelectric coupling in the Fe/BaTiO₃ system.

Increasing d-wave superconductivity by on-site repulsion.

We study, through the variational Monte Carlo technique, an extended Hubbard model away from half filled band density which contains two competing nearest-neighbor interactions: a superexchange J favoring d-wave superconductivity and a repulsion V opposing it. We find that the on-site repulsion U effectively enhances the strength of J while suppressing that of V, thus favoring superconductivity. This result shows that attractions which do not involve charge fluctuations are very well equipped against strong electron-electron repulsion so much to get advantage from it.