TY - JOUR A1 - Rinaldi, Christian A1 - Varotto, Sara A1 - Asa, Marco A1 - Slawinska, Jagoda A1 - Fujii, Jun A1 - Vinai, Giovanni A1 - Cecchi, Stefano A1 - Di Sante, Domenico A1 - Calarco, Raffaella A1 - Vobornik, Ivana A1 - Panaccione, Giancarlo A1 - Picozzi, Silvia A1 - Bertacco, Riccardo T1 - Ferroelectric Control of the Spin Texture in GeTe JF - Nano Letters N2 - The electric and nonvolatile control of the spin texture in semiconductors would represent a fundamental step toward novel electronic devices combining memory and computing functionalities. Recently, GeTe has been theoretically proposed as the father compound of a new class of materials, namely ferroelectric Rashba semiconductors. They display bulk bands with giant Rashba-like splitting due to the inversion symmetry breaking arising from the ferroelectric polarization, thus allowing for the ferroelectric control of the spin. Here, we provide the experimental demonstration of the correlation between ferroelectricity and spin texture. A surface-engineering strategy is used to set two opposite predefined uniform ferroelectric polarizations, inward and outward, as monitored by piezoresponse force microscopy. Spin and angular resolved photoemission experiments show that these GeTe(111) surfaces display opposite sense of circulation of spin in bulk Rashba bands. Furthermore, we demonstrate the crafting of nonvolatile ferroelectric patterns in GeTe films at the nanoscale by using the conductive tip of an atomic force microscope. Based on the intimate link between ferroelectric polarization and spin in GeTe, ferroelectric patterning paves the way to the investigation of devices with engineered spin configurations. KW - Germanium telluride KW - Rashba effect KW - ferroelectricity KW - spin-orbitronics Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-226294 VL - 18 IS - 5 ER - TY - JOUR A1 - Di Sante, Domenico A1 - Erdmenger, Johanna A1 - Greiter, Martin A1 - Matthaiakakis, Ioannis A1 - Meyer, René A1 - Fernandez, David Rodríguez A1 - Thomale, Ronny A1 - van Loon, Erik A1 - Wehling, Tim T1 - Turbulent hydrodynamics in strongly correlated Kagome metals JF - Nature Communications N2 - A current challenge in condensed matter physics is the realization of strongly correlated, viscous electron fluids. These fluids can be described by holography, that is, by mapping them onto a weakly curved gravitational theory via gauge/gravity duality. The canonical system considered for realizations has been graphene. In this work, we show that Kagome systems with electron fillings adjusted to the Dirac nodes provide a much more compelling platform for realizations of viscous electron fluids, including non-linear effects such as turbulence. In particular, we find that in Scandium Herbertsmithite, the fine-structure constant, which measures the effective Coulomb interaction, is enhanced by a factor of about 3.2 as compared to graphene. We employ holography to estimate the ratio of the shear viscosity over the entropy density in Sc-Herbertsmithite, and find it about three times smaller than in graphene. These findings put the turbulent flow regime described by holography within the reach of experiments. Viscous electron fluids are predicted in strongly correlated systems but remain challenging to realize. Here, the authors predict enhanced effective Coulomb interaction and reduced ratio of the shear viscosity over entropy density in a Kagome metal, inferring turbulent flow of viscous electron fluids. KW - coupling-constant dependence KW - shear viscosity KW - electron KW - resistance Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230380 VL - 11 ER - TY - JOUR A1 - Ciuchi, Sergio A1 - Di Sante, Domenico A1 - Dobrosavljević, Vladimir A1 - Fratini, Simone T1 - The origin of Mooij correlations in disordered metals JF - npj Quantum Materials N2 - Sufficiently disordered metals display systematic deviations from the behavior predicted by semi-classical Boltzmann transport theory. Here the scattering events from impurities or thermal excitations can no longer be considered as additive-independent processes, as asserted by Matthiessen’s rule following from this picture. In the intermediate region between the regime of good conduction and that of insulation, one typically finds a change of sign of the temperature coefficient of resistivity, even at elevated temperature spanning ambient conditions, a phenomenology that was first identified by Mooij in 1973. Traditional weak coupling approaches to identify relevant corrections to the Boltzmann picture focused on long-distance interference effects such as “weak localization”, which are especially important in low dimensions (1D and 2D) and close to the zero-temperature limit. Here we formulate a strong-coupling approach to tackle the interplay of strong disorder and lattice deformations (phonons) in bulk three-dimensional metals at high temperatures. We identify a polaronic mechanism of strong disorder renormalization, which describes how a lattice locally responds to the relevant impurity potential. This mechanism, which quantitatively captures the Mooij regime, is physically distinct and unrelated to Anderson localization, but realizes early seminal ideas of Anderson himself, concerning the interplay of disorder and lattice deformations. KW - electronic properties and materials KW - phase transitions and critical phenomena KW - theory and computation Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-223148 VL - 3 ER -