TY - GEN A1 - Seibold, Götz A1 - Caprara, Sergio A1 - Grilli, Marco A1 - Raimondi, Roberto T1 - Intrinsic spin Hall effect in systems with striped spin-orbit coupling T2 - epl : a letters journal exploring the frontiers of physics KW - Condensed Matter Y1 - 2015 UR - http://epljournal.edpsciences.org/articles/epl/abs/2015/19/epl17411/epl17411.html U6 - https://doi.org/http://dx.doi.org/10.1209/0295-5075/112/17004 SN - 1286-4854 VL - 112 IS - 1 SP - 17004-p1 EP - 17004-p6 ER - TY - GEN A1 - Bucheli, Daniel A1 - Grilli, Marco A1 - Peronaci, F. A1 - Seibold, Götz A1 - Caprara, Sergio T1 - Phase diagrams of voltage-gated oxide interfaces with strong Rashba coupling T2 - Physical Review B N2 - We propose a model for the two-dimensional electron gas formed at the interface of oxide heterostructures that includes a Rashba spin-orbit coupling proportional to an electric field oriented perpendicularly to the interface. Taking into account the electron density dependence of this electric field confining the electron gas at the interface, we report the occurrence of a phase separation instability (signaled by a negative compressibility) for realistic values of the spin-orbit coupling and of the electronic band-structure parameters at zero temperature. We extend the analysis to finite temperatures and in the presence of an in-plane magnetic field, thereby obtaining two phase diagrams that exhibit a phase separation dome. By varying the gating potential, the phase separation dome may shrink and vanish at zero temperature into a quantum critical point where the charge fluctuates dynamically. Similarly, the phase separation may be spoiled by a planar magnetic field even at zero temperature leading to a line of quantum critical points. Y1 - 2014 UR - https://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.195448 U6 - https://doi.org/10.1103/PhysRevB.89.195448 SN - 2469-9969 VL - 89 ER - TY - GEN A1 - Seibold, Götz A1 - Caprara, Sergio A1 - Grilli, Marco A1 - Raimondi, Roberto T1 - Non-equilibrium Spin Currents in Systems with Striped Rashba Spin-Orbit Coupling T2 - Journal of Superconductivity and Novel Magnetism N2 - It is shown that non-homogeneity in the spin-orbit coupling (SOC) arising from structure inversion asymmetry gives rise to a finite intrinsic spin Hall conductivity in contrast with the corresponding case of a homogeneous SOC in the disordered two-dimensional electron gas. In particular, we examine the inhomogeneity arising from a striped modulation of the Rashba type spin-orbit coupling. A corresponding structure could be realized at oxide interfaces with periodic top gating or in semiconductor heterostructures. Y1 - 2017 UR - http://link.springer.com/article/10.1007/s10948-016-3774-x U6 - https://doi.org/10.1007/s10948-016-3774-x SN - 1557-1939 VL - 30 IS - 1 SP - 123 EP - 128 ER - TY - GEN A1 - Caprara, Sergio A1 - Grilli, Marco A1 - Di Castro, Carlo A1 - Seibold, Götz T1 - Pseudogap and (An)isotropic Scattering in the Fluctuating Charge-Density Wave Phase of Cuprates T2 - Journal of Superconductivity and Novel Magnetism N2 - We present a general scenario for high-temperature superconducting cuprates, based on the presence of dynamical charge density waves (CDWs) and to the occurrence of a CDW quantum critical point, which occurs, e.g., at doping p ≈ 0.16 in YBa2Cu3O6 + δ (YBCO). In this framework, the pseudogap temperature T∗ is interpreted in terms of a reduction of the density of states due to incipient CDW and, at lower temperature to the possible formation of incoherent superconducting pairs. The dynamically fluctuating character of CDW accounts for the different temperatures at which the CDW onset revealed by X-ray scattering (Tons(p)), and the static three-dimensional CDW ordering appear. We also investigate the anisotropic character of the CDW-mediated scattering. We find that this is strongly anisotropic only close to the CDW quantum critical point (QCP) at low temperature and very low energy. It rapidly becomes nearly isotropic and marginal-Fermi-liquid-like away from the CDW QCP and at finite (even rather small) energies. This may reconcile the interpretation of Hall measurements in terms of anisotropic CDW scattering with recent photoemission experiments Bok, J.M., et al. Sci. Adv. 2, e1501329 (2016). KW - Charge-density waves KW - High-Tc superconducting cuprates KW - Anisotropic scattering Y1 - 2017 UR - http://link.springer.com/article/10.1007/s10948-016-3775-9 U6 - https://doi.org/10.1007/s10948-016-3775-9 SN - 1557-1939 SN - 1557-1947 VL - 30 IS - 1 SP - 25 EP - 30 ER - TY - GEN A1 - Bovenzi, Nicolo A1 - Finocchiaro, Francesca A1 - Scopigno, Nicantro A1 - Bucheli, Daniel A1 - Caprara, Sergio A1 - Seibold, Götz A1 - Grilli, Marco T1 - Possible Mechanisms of Electronic Phase Separation in Oxide Interfaces T2 - Journal of Superconductivity and Novel Magnetism N2 - LaAlO 3/SrTiO 3 and LaTiO 3/SrTiO 3 (LXO / STO) interfaces are known to host a strongly inhomogeneous (nearly) two-dimensional electron gas (2DEG). In this work, we present three unconventional electronic mechanisms of electronic phase separation (EPS) in a 2DEG as a possible source of inhomogeneity in oxide interfaces. Common to all three mechanisms is the dependence of some (interaction) potential on the 2DEGs density. We first consider a mechanism resulting from a sizable density-dependent Rashba spin-orbit coupling. Next, we point out that an EPS may also occur in the case of a density-dependent superconducting pairing interaction. Finally, we show that the confinement of the 2DEG to the interface by a density-dependent, self-consistent electrostatic potential can by itself cause an EPS. KW - Oxide interfaces KW - Superconductivity KW - Electronic phase separation Y1 - 2015 UR - http://link.springer.com/article/10.1007/s10948-014-2903-7 U6 - https://doi.org/10.1007/s10948-014-2903-7 SN - 1557-1939 SN - 1557-1947 VL - 28 IS - 4 SP - 1273 EP - 1277 ER - TY - GEN A1 - Seibold, Götz A1 - Bucheli, Daniel A1 - Caprara, Sergio A1 - Grilli, Marco T1 - Phase separation and long-wavelength charge instabilities in spin-orbit coupled systems T2 - EPL Europhysics Letters N2 - We investigate a two-dimensional electron model with Rashba spin-orbit interaction where the coupling constant $g=g(n)$ depends on the electronic density. It is shown that this dependence may drive the system unstable towards a long-wavelength charge density wave (CDW) where the associated second-order instability occurs in close vicinity to global phase separation. For very low electron densities the CDW instability is nesting-induced and the modulation follows the Fermi momentum kF. At higher density the instability criterion becomes independent of kF and the system may become unstable in a broad momentum range. Finally, upon filling the upper spin-orbit split band, finite momentum instabilities disappear in favor of phase separation alone. We discuss our results with regard to the inhomogeneous phases observed at the LaAlO3/SrTiO3 or LaTiO3/SrTiO3 interfaces. Y1 - 2015 UR - http://iopscience.iop.org/article/10.1209/0295-5075/109/17006;jsessionid=34AAE2057398BD7AE51C0C4719FC29DD.c2.iopscience.cld.iop.org U6 - https://doi.org/10.1209/0295-5075/109/17006 SN - 1286-4854 VL - 109 IS - 1 SP - 17006 ER - TY - GEN A1 - Seibold, Götz A1 - Caprara, Sergio A1 - Grilli, Marco A1 - Raimondi, Roberto T1 - Inhomogeneous Rashba spin–orbit coupling and intrinsic spin-Hall effect T2 - Journal of Magnetism and Magnetic Materials N2 - The spin-Hall effect is the generation of a transverse spin-current induced by a longitudinal electric field. Among the various scattering mechanisms which can induce a finite spin-Hall effect we focus on the intrinsic contribution arising from a Rashba-type spin–orbit (RSO) coupling which for couplings linear in momentum usually vanishes. Here we show that non-homogeneity in the spin–orbit coupling arising from structure inversion asymmetry gives rise to a finite spin-Hall effect which we exemplify for a system with striped Rashba spin–orbit coupling. KW - Spin Hall effect KW - Rashba spin–orbit coupling KW - Inhomogeneity Y1 - 2016 UR - http://www.sciencedirect.com/science/article/pii/S0304885316317772 U6 - https://doi.org/10.1016/j.jmmm.2016.12.066 VL - 440 SP - 63 EP - 65 ER - TY - GEN A1 - Capati, Matteo A1 - Caprara, Sergio A1 - Di Castro, Carlo A1 - Grilli, Marco A1 - Seibold, Götz A1 - Lorenzana, José T1 - Electronic polymers and soft-matter-like broken symmetries in underdoped cuprates T2 - Nature Communications N2 - Empirical evidence in heavy fermion, pnictide and other systems suggests that unconventional superconductivity appears associated to some form of real-space electronic order. For the cuprates, despite several proposals, the emergence of order in the phase diagram between the commensurate antiferromagnetic state and the superconducting state is not well understood. Here we show that in this regime doped holes assemble in ‘electronic polymers’. Within a Monte Carlo study, we find that in clean systems by lowering the temperature the polymer melt condenses first in a smectic state and then in a Wigner crystal both with the addition of inversion symmetry breaking. Disorder blurs the positional order leaving a robust inversion symmetry breaking and a nematic order, accompanied by vector chiral spin order and with the persistence of a thermodynamic transition. Such electronic phases, whose properties are reminiscent of soft-matter physics, produce charge and spin responses in good accord with experiments. KW - Molecular electronics KW - Polymers KW - Superconducting properties and materials Y1 - 2015 UR - http://www.nature.com/articles/ncomms8691 U6 - https://doi.org/doi:10.1038/ncomms8691 SN - 2041-1723 VL - 6 SP - 7691 ER - TY - GEN A1 - Caprara, Sergio A1 - Di Castro, Carlo A1 - Seibold, Götz A1 - Grilli, Marco T1 - Dynamical charge density waves rule the phase diagram of cuprates T2 - Physical Review B N2 - In the last few years, charge density waves (CDWs) have been ubiquitously observed in high-temperature superconducting cuprates and are now the most investigated among the competing orders in the still hot debate on these systems. A wealth of new experimental data raises several fundamental issues that challenge the various theoretical proposals. We here relate our mean-field instability line T0CDW of a strongly correlated Fermi liquid to the pseudogap T∗(p) line, marking in this way the onset of CDW-fluctuations. These fluctuations reduce strongly the mean-field critical line. Controlling this reduction via an infrared frequency cutoff related to the characteristic time of the probes, we account for the complex experimental temperature versus doping phase diagram. We provide a coherent scenario explaining why different CDW onset curves are observed by different experimental probes and seem to extrapolate at zero temperature into seemingly different quantum critical points (QCPs) in the intermediate and overdoped region. The nearly singular anisotropic scattering mediated by these fluctuations also accounts for the rapid changes of the Hall number seen in experiments and provides the first necessary step for a possible Fermi surface reconstruction fully establishing at lower doping. Finally, we show that phase fluctuations of the CDWs, which are enhanced in the presence of strong correlations near the Mott insulating phase, naturally account for the disappearance of the CDWs at low doping with yet another QCP as seen by the experiments. Y1 - 2017 UR - https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.224511 U6 - https://doi.org/https://doi.org/10.1103/PhysRevB.95.224511 SN - 2469-9950 SN - 2469-9969 VL - 95 IS - 22 SP - 224511 ER - TY - GEN A1 - Bovenzi, Nicandro A1 - Caprara, Sergio A1 - Grilli, Marco A1 - Raimondi, Roberto A1 - Scopigno, Niccolò A1 - Seibold, Götz T1 - Density inhomogeneities and Rashba spin-orbit coupling interplay in oxide interfaces T2 - Journal of Physics and Chemistry of Solids N2 - There is steadily increasing evidence that the two-dimensional electron gas (2DEG) formed at the interface of some insulating oxides like LaAlO3/SrTiO3 and LaTiO3/SrTiO3 is strongly inhomogeneous. The inhomogeneous distribution of electron density is accompanied by an inhomogeneous distribution of the (self-consistent) electric field confining the electrons at the interface. In turn this inhomogeneous transverse electric field induces an inhomogeneous Rashba spin-orbit coupling (RSOC). After an introductory summary on two mechanisms possibly giving rise to an electronic phase separation accounting for the above inhomogeneity, we introduce a phenomenological model to describe the density-dependent RSOC and its consequences. Besides being itself a possible source of inhomogeneity or charge-density waves, the density-dependent RSOC gives rise to interesting physical effects like the occurrence of inhomogeneous spin-current distributions and inhomogeneous quantum-Hall states with chiral “edge” states taking place in the bulk of the 2DEG. The inhomogeneous RSOC can also be exploited for spintronic devices since it can be used to produce a disorder-robust spin Hall effect. Y1 - 2017 UR - https://www.sciencedirect.com/science/article/pii/S0022369717305991 SN - 0022-3697 ER -