@article{RinaldiVarottoAsaetal.2018, author = {Rinaldi, Christian and Varotto, Sara and Asa, Marco and Slawinska, Jagoda and Fujii, Jun and Vinai, Giovanni and Cecchi, Stefano and Di Sante, Domenico and Calarco, Raffaella and Vobornik, Ivana and Panaccione, Giancarlo and Picozzi, Silvia and Bertacco, Riccardo}, title = {Ferroelectric Control of the Spin Texture in GeTe}, series = {Nano Letters}, volume = {18}, journal = {Nano Letters}, number = {5}, doi = {10.1021/acs.nanolett.7b04829}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226294}, pages = {2751-2758}, year = {2018}, abstract = {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.}, language = {en} } @article{CiuchiDiSanteDobrosavljevićetal.2018, author = {Ciuchi, Sergio and Di Sante, Domenico and Dobrosavljević, Vladimir and Fratini, Simone}, title = {The origin of Mooij correlations in disordered metals}, series = {npj Quantum Materials}, volume = {3}, journal = {npj Quantum Materials}, doi = {10.1038/s41535-018-0119-y}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-223148}, year = {2018}, abstract = {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.}, language = {en} }