TY - GEN A1 - Seibold, Götz A1 - Caprara, Sergio A1 - Grilli, Marco A1 - Raimondi, Roberto T1 - Theory of the Spin Galvanic Effect at Oxide Interfaces T2 - Physical Review Letters N2 - The spin galvanic effect (SGE) describes the conversion of a nonequilibrium spin polarization into a transverse charge current. Recent experiments have demonstrated a large conversion efficiency for the two-dimensional electron gas formed at the interface between two insulating oxides, LaAlO3 and SrTiO3. Here, we analyze the SGE for oxide interfaces within a three-band model for the Ti t2g orbitals which displays an interesting variety of effective spin-orbit couplings in the individual bands that contribute differently to the spin-charge conversion. Our analytical approach is supplemented by a numerical treatment where we also investigate the influence of disorder and temperature, which turns out to be crucial to providing an appropriate description of the experimental data. KW - Spin polarization KW - Spin-orbit coupling KW - Spintronics KW - Two-dimensional electron gas Y1 - 2017 UR - https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.256801 U6 - https://doi.org/10.1103/PhysRevLett.119.256801 SN - 1092-0145 VL - 119 IS - 25 ER - 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 - Caprara, Sergio A1 - Di Castro, Carlo A1 - Mirarchi, Giovanni A1 - Seibold, Götz A1 - Grilli, Marco T1 - Dissipation-driven strange metal behavior T2 - Communications Physics N2 - Anomalous metallic properties are often observed in the proximity of quantum critical points, with violation of the Fermi Liquid paradigm. We propose a scenario where, near the quantum critical point, dynamical fluctuations of the order parameter with finite correlation length mediate a nearly isotropic scattering among the quasiparticles over the entire Fermi surface. This scattering produces a strange metallic behavior, which is extended to the lowest temperatures by an increase of the damping of the fluctuations. We phenomenologically identify one single parameter ruling this increasing damping when the temperature decreases, accounting for both the linear-in-temperature resistivity and the seemingly divergent specific heat observed, e.g., in high-temperature superconducting cuprates and some heavy-fermion metals. KW - Electronic properties and materials KW - Superconducting properties and materials Y1 - 2022 UR - https://www.nature.com/articles/s42005-021-00786-y U6 - https://doi.org/10.1038/s42005-021-00786-y SN - 2399-3650 IS - 5 SP - 1 EP - 7 ER - TY - GEN A1 - Seibold, Götz A1 - Arpaia, Riccardo A1 - Ying Ying, Peng A1 - Fumagalli, Roberto A1 - Braicovich, Lucio A1 - Di Castro, Carlo A1 - Grilli, Marco A1 - Ghiringhelli, Giacomo Claudio A1 - Caprara, Sergio T1 - Strange metal behaviour from charge density fluctuations in cuprates T2 - Communications Physics N2 - Besides the mechanism responsible for high critical temperature superconductivity, the grand unresolved issue of the cuprates is the occurrence of a strange metallic state above the so-called pseudogap temperature T*. Even though such state has been successfully described within a phenomenological scheme, the so-called Marginal Fermi-Liquid theory, a microscopic explanation is still missing. However, recent resonant X-ray scattering experiments identified a new class of charge density fluctuations characterized by low characteristic energies and short correlation lengths, which are related to the well-known charge density waves. These fluctuations are present over a wide region of the temperature-vs-doping phase diagram and extend well above T*. Here we investigate the consequences of charge density fluctuations on the electron and transport properties and find that they can explain the strange metal phenomenology. Therefore, charge density fluctuations are likely the long-sought microscopic mechanism underlying the peculiarities of the metallic state of cuprates. KW - Electronic properties and materials KW - Superconducting properties and materials Y1 - 2021 UR - https://www.nature.com/articles/s42005-020-00505-z U6 - https://doi.org/10.1038/s42005-020-00505-z SN - 2399-3650 VL - 4 SP - 1 EP - 6 ER - TY - GEN A1 - Mirarchi, Giovanni A1 - Seibold, Götz A1 - Di Castro, Carlo A1 - Grilli, Marco A1 - Caprara, Sergio T1 - The Strange-Metal Behavior of Cuprates T2 - Condensed Matter N2 - Recent resonant X-ray scattering experiments on cuprates allowed to identify a new kind of collective excitations, known as charge density fluctuations, which have finite characteristic wave vector, short correlation length and small characteristic energy. It was then shown that these fluctuations provide a microscopic scattering mechanism that accounts for the anomalous transport properties of cuprates in the so-called strange-metal phase and are a source of anomalies in the specific heat. In this work, we retrace the main steps that led us to attributing a central role to charge density fluctuations in the strange-metal phase of cuprates, discuss the state of the art on the issue and provide an in-depth analysis of the contribution of charge density fluctuations to the specific heat. KW - high-temperature superconductors KW - cuprates KW - charge density fluctuations KW - strange metal KW - dynamical quantum criticality Y1 - 2022 UR - https://www.mdpi.com/2410-3896/7/1/29/htm U6 - https://doi.org/10.3390/condmat7010029 SN - 2410-3896 VL - 7 IS - 1 SP - 1 EP - 17 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 - 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 - Wahlberg, Eric A1 - Arpaia, Riccardo A1 - Seibold, Götz A1 - Rossi, Matteo A1 - Fumagalli, Roberto A1 - Trabaldo, Edoardo A1 - Brookes, Nicholas B. A1 - Braicovich, Lucio A1 - Caprara, Sergio A1 - Lombardi, Floriana A1 - Gran, Ulf A1 - Ghiringhelli, Giacomo Claudio A1 - Bauch, Thilo T1 - Restored strange metal phase through suppression of charge density waves in underdoped YBa2Cu3O7–δ T2 - Science N2 - The normal state of optimally doped cuprates is dominated by the “strange metal” phase that shows a linear temperature (T) dependence of the resistivity persisting down to the lowest T. For underdoped cuprates, this behavior is lost below the pseudogap temperature T*, where charge density waves (CDWs), together with other intertwined local orders, characterize the ground state. We found that the T-linear resistivity of highly strained, ultrathin, underdoped YBa2Cu3O7–δ films is restored when the CDW amplitude, detected by resonant inelastic x-ray scattering, is suppressed. This observation suggests an intimate connection between the onset of CDWs and the departure from T-linear resistivity in underdoped cuprates. Our results illustrate the potential of using strain control to manipulate the ground state of quantum materials. KW - Cuprate superconductors KW - Charge-Density Wave Y1 - 2021 UR - https://www.science.org/doi/10.1126/science.abc8372 U6 - https://doi.org/10.1126/science.abc8372 VL - 373 IS - 6562 SP - 1506 EP - 1510 ER - TY - GEN A1 - Grilli, Marco A1 - Di Castro, Carlo A1 - Mirarchi, Giovanni A1 - Seibold, Götz A1 - Caprara, Sergio T1 - Dissipative Quantum Criticality as a Source of Strange Metal Behavior T2 - Symmetry N2 - The strange metal behavior, usually characterized by a linear-in-temperature (T) resistivity, is a still unsolved mystery in solid-state physics. It is often associated with the proximity to a quantum critical point (a second order transition at temperature T=0, leading to a broken symmetry phase) focusing on the related divergent order parameter correlation length. Here, we propose a paradigmatic shift, focusing on a divergent characteristic time scale due to a divergent dissipation acting on the fluctuating critical modes while their correlation length stays finite. To achieve a divergent dissipation, we propose a mechanism based on the coupling between a local order parameter fluctuation and electron density diffusive modes that accounts both for the linear-in-T resistivity and for the logarithmic specific heat versus temperature ratio CV/T∼log(1/T), down to low temperatures. KW - strange metal behavior KW - cuprates KW - charge density fluctuations KW - diffusive modes Y1 - 2023 U6 - https://doi.org/10.3390/sym15030569 SN - 2073-8994 VL - 15 IS - 3 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 - Mirarchi, Giovanni A1 - Grilli, Marco A1 - Seibold, Götz A1 - Caprara, Sergio T1 - The Shrinking Fermi Liquid Scenario for Strange-Metal Behavior from Overdamped Optical Phonons T2 - Condensed Matter N2 - We discuss how the interaction of electrons with an overdamped optical phonon can give rise to a strange-metal behavior over extended temperature and frequency ranges. Although the mode has a finite frequency, an increasing damping shifts spectral weight to progressively lower energies so that despite the ultimate Fermi liquid character of the system at the lowest temperatures and frequencies, the transport and optical properties of the electron system mimic a marginal Fermi liquid behavior. Within this shrinking Fermi liquid scenario, we extensively investigate the electron self-energy in all frequency and temperature ranges, emphasizing similarities and differences with respect to the marginal Fermi liquid scenario. KW - strange-metal behavior KW - marginal Fermi liquid KW - high-temperature cuprate superconductors Y1 - 2024 UR - https://www.mdpi.com/2410-3896/9/1/14 U6 - https://doi.org/10.3390/condmat9010014 SN - 2410-3896 VL - 9 IS - 1 SP - 1 EP - 13 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 - 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 - 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 - 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 - TY - CHAP A1 - Seibold, Götz A1 - Caprara, Sergio A1 - Raimondi, Roberto ED - Drouhin, Henri-Jean ED - Wegrowe, Jean-Eric ED - Razeghi, Manijeh ED - Jaffrès, Henri T1 - Theory of charge-spin conversion at oxide interfaces: the inverse spin-galvanic effect T2 - Spintronics XI, SPIE Nanoscience + Engineering, 19-23 August 2018, San Diego, California, United States N2 - We evaluate the non-equilibrium spin polarization induced by an applied electric field for a tight-binding model of electron states at oxides interfaces in LAO/STO heterostructures. By a combination of analytic and numerical approaches we investigate how the spin texture of the electron eigenstates due to the interplay of spin-orbit coupling and inversion asymmetry determines the sign of the induced spin polarization as a function of the chemical potential or band filling, both in the absence and presence of local disorder. With the latter, we find that the induced spin polarization evolves from a non monotonous behavior at zero temperature to a monotonous one at higher temperature. Our results may provide a sound framework for the interpretation of recent experiments. Y1 - 2018 UR - https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10732/107322P/Theory-of-charge-spin-conversion-at-oxide-interfaces--the/10.1117/12.2319592.short U6 - https://doi.org/10.1117/12.2319592 PB - Spie CY - Bellingham, USA 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 - Caprara, Sergio A1 - Grilli, Marco A1 - Raimondi, Roberto T1 - On the Evaluation of the Spin Galvanic Effect in Lattice Models with Rashba Spin-Orbit Coupling T2 - Condensed matter N2 - The spin galvanic effect (SGE) describes the conversion of a non-equilibrium spin polarization into a charge current and has recently attracted renewed interest due to the large conversion efficiency observed in oxide interfaces. An important factor in the SGE theory is disorder which ensures the stationarity of the conversion. Through this paper, we propose a procedure for the evaluation of the SGE on disordered lattices which can also be readily implemented for multiband systems. We demonstrate the performance of the method for a single-band Rashba model and compare our results with those obtained within the self-consistent Born approximation for a continuum model. KW - spintronics KW - spin-galvanic effect KW - lattice models Y1 - 2018 UR - http://www.mdpi.com/2410-3896/3/3/22 U6 - https://doi.org/10.3390/condmat3030022 SN - 2410-3896 VL - 3 IS - 33 SP - 1 EP - 10 ER -