Author Correction: Fermiology and electron dynamics of trilayer nickelate La4Ni3O10.

The original version of this Article contained errors in Fig. 2, Fig. 3a-c and Supplementary Fig. 2. In Fig. 2g and Supplementary Fig. 2, the band structure plot calculated from density function theory (DFT) had a missing band of mainly z2 character that starts at about - 0.25 eV at the Y point and disperses downwards towards the Γ point. This band was inadvertently neglected when transferring the lines from the original band plot to the enhanced version for publication. Also in Fig. 2g, the points labelled M and Y were not exactly at (1/2 1/2 0) and (0 1/2 0), but rather (0.52 0.48 0) and (0 0.48 0) due to a bug in XCrysDen for low-symmetry structures that the authors failed to identify before publication. Thus, the bands presented were slightly off the true M-Y direction and additional splitting incorrectly appeared (in particular for the highly dispersive bands of x2-y2 character). The correct versions of Fig. 2g (cited as Fig. 1) and Supplementary Fig. 2 (cited as Fig. 2) are:which replaces the previous incorrect version, cited here as Fig. 3 and Fig. 4:Neither of these errors in Fig. 2g or Supplementary Fig. 2 affects either the discussion or any of the interpretations of the ARPES data provided in the paper. The authors discussed the multilayer band splitting along the Γ-M direction (δ band and α band as assigned in the paper), and ARPES did not see any split band. The authors did not discuss the further splitting that arises due to back folding along the M-Y direction.In Fig. 3a-c, the errors in the M and Y points in Fig. 2g cause subtle changes to the DFT dispersions. The correct version of Fig. 3a-c is cited here as Fig 5:which replaces the previous incorrect version (Fig. 6):However, the influence on the effective mass results of Fig. 3d is negligible.These errors have now been corrected in both the PDF and HTML versions of the Article. The authors acknowledge James Rondinelli and Danilo Puggioni from Northwestern University for calling our attention to these issues

Local Moment Instability of Os in Honeycomb Li2.15Os0.85O3.

Compounds with honeycomb structures occupied by strong spin orbit coupled (SOC) moments are considered to be candidate Kitaev quantum spin liquids. Here we present the first example of Os on a honeycomb structure, Li2.15(3)Os0.85(3)O3 (C2/c, a = 5.09 Å, b = 8.81 Å, c = 9.83 Å, β = 99.3°). Neutron diffraction shows large site disorder in the honeycomb layer and X-ray absorption spectroscopy indicates a valence state of Os (4.7 ± 0.2), consistent with the nominal concentration. We observe a transport band gap of Δ = 243 ± 23 meV, a large van Vleck susceptibility, and an effective moment of 0.85 μB, much lower than expected from 70% Os(+5). No evidence of long range order is found above 0.10 K but a spin glass-like peak in ac-susceptibility is observed at 0.5 K. The specific heat displays an impurity spin contribution in addition to a power law ∝T(0.63±0.06). Applied density functional theory (DFT) leads to a reduced moment, suggesting incipient itineracy of the valence electrons, and finding evidence that Li over stoichiometry leads to Os(4+)-Os(5+) mixed valence. This local picture is discussed in light of the site disorder and a possible underlying quantum spin liquid state

Polarons and confinement of electronic motion to two dimensions in a layered transition metal oxide

A very remarkable feature of the layered transition metal oxides (TMOs), whose most famous members are the high-temperature superconductors (HTSs), is that even though they are prepared as bulk three-dimensional single crystals, they display hugely anisotropic electrical and optical properties, seeming to be insulating perpendicular to the layers and metallic within them. This is the phenomenon of confinement, a concept at odds with the conventional theory of solids and recognized as due to magnetic and electron-lattice interactions in the layers which must be overcome at a substantial energy cost if electrons are to be transferred between layers. The associated energy gap or 'pseudogap' is particularly obvious in experiments where charge is moved perpendicular to the planes, most notably scanning tunneling microscopy (STM) and polarized infrared spectroscopy. Here, using the same experimental tools, we show that there is a second family of TMOs - the layered manganites La2-2xSr1+2xMn2O7 (LSMO) - with even more extreme confinement and pseudogap effects. The data, which are the first to resolve atoms in any metallic manganite, demonstrate quantitatively that because they are attached to polarons - lattice and spin textures within the planes -, it is equally difficult to remove carriers from the planes via vacuum tunneling into a conventional metallic tip, as it is for them to move between Mn-rich layers within the material itself

The Hubbard model within the equations of motion approach

The Hubbard model has a special role in Condensed Matter Theory as it is considered as the simplest Hamiltonian model one can write in order to describe anomalous physical properties of some class of real materials. Unfortunately, this model is not exactly solved except for some limits and therefore one should resort to analytical methods, like the Equations of Motion Approach, or to numerical techniques in order to attain a description of its relevant features in the whole range of physical parameters (interaction, filling and temperature). In this manuscript, the Composite Operator Method, which exploits the above mentioned analytical technique, is presented and systematically applied in order to get information about the behavior of all relevant properties of the model (local, thermodynamic, single- and two- particle ones) in comparison with many other analytical techniques, the above cited known limits and numerical simulations. Within this approach, the Hubbard model is shown to be also capable to describe some anomalous behaviors of the cuprate superconductors.Comment: 232 pages, more than 300 figures, more than 500 reference

Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites

A characteristic feature of the copper oxide high-temperature superconductors is the dichotomy between the electronic excitations along the nodal (diagonal) and antinodal (parallel to the Cu-O bonds) directions in momentum space, generally assumed to be linked to the "d-wave" symmetry of the superconducting state. Angle-resolved photoemission measurements in the superconducting state have revealed a quasiparticle spectrum with a d-wave gap structure that exhibits a maximum along the antinodal direction and vanishes along the nodal direction. Subsequent measurements have shown that, at low doping levels, this gap structure persists even in the high-temperature metallic state, although the nodal points of the superconducting state spread out in finite "Fermi arcs". This is the so-called pseudogap phase, and it has been assumed that it is closely linked to the superconducting state, either by assigning it to fluctuating superconductivity or by invoking orders which are natural competitors of d-wave superconductors. Here we report experimental evidence that a very similar pseudogap state with a nodal-antinodal dichotomous character exists in a system that is markedly different from a superconductor: the ferromagnetic metallic groundstate of the colossal magnetoresistive bilayer manganite La1.2Sr1.8Mn2O7. Our findings therefore cast doubt on the assumption that the pseudogap state in the copper oxides and the nodal-antinodal dichotomy are hallmarks of the superconductivity state.Comment: To appear in Natur

Dynamics of bi-stripes and a colossal metal-insulator transition in the bi-layer manganite La2−2x_{2-2x}Sr1+2x_{1+2x}Mn2_{2}O7_{7} (x~0.59)

In correlated electron materials, electrons often self-organize and form a variety of patterns with potential ordering of charges, spins, and orbitals, which are believed to be closely connected to many novel properties of these materials including superconductivity, metal-insulator transitions, and the CMR effect. How these real-space patterns affect the conductivity and other properties of materials (which are usually described in momentum space) is one of the major challenges of modern condensed matter physics. Moreover, although the presence of static stripes is indisputable, the existence (and potential impacts) of fluctuating stripes in such compounds is a subject of great debate. Here we present the electronic excitations of La$_{2-2x}$Sr$_{1+2x}$Mn$_{2}$O$_{7}$ (x ~ 0.59) probed by angle-resolved photoemission (ARPES), from which we demonstrate that a novel type of ordering, termed bi-stripes, can exhibit either static or fluctuating order as a function of temperature. We found that the static bi-stripe order is especially damaging to electrical conductivity, completely localizing the electrons in the bi-stripe regions, while the fluctuating stripes can coexist with mobile carriers. This physics drives a novel phase transition with colossal conductivity changes as a function of temperature. Our finding suggests that quantum stripes can give rise to electronic properties significantly different from their static counterparts. Inducing transition between them can turn on remarkable electronic phenomena, enriching our understanding of correlated electron systems as well as opening a window for potential applications in electronic devices

Dynamics of bi-stripes and a colossal metal-insulator transition in the bi-layer manganite La2−2x_{2-2x}Sr1+2x_{1+2x}Mn2_{2}O7_{7} (x~0.59)

In correlated electron materials, electrons often self-organize and form a variety of patterns with potential ordering of charges, spins, and orbitals, which are believed to be closely connected to many novel properties of these materials including superconductivity, metal-insulator transitions, and the CMR effect. How these real-space patterns affect the conductivity and other properties of materials (which are usually described in momentum space) is one of the major challenges of modern condensed matter physics. Moreover, although the presence of static stripes is indisputable, the existence (and potential impacts) of fluctuating stripes in such compounds is a subject of great debate. Here we present the electronic excitations of La$_{2-2x}$Sr$_{1+2x}$Mn$_{2}$O$_{7}$ (x ~ 0.59) probed by angle-resolved photoemission (ARPES), from which we demonstrate that a novel type of ordering, termed bi-stripes, can exhibit either static or fluctuating order as a function of temperature. We found that the static bi-stripe order is especially damaging to electrical conductivity, completely localizing the electrons in the bi-stripe regions, while the fluctuating stripes can coexist with mobile carriers. This physics drives a novel phase transition with colossal conductivity changes as a function of temperature. Our finding suggests that quantum stripes can give rise to electronic properties significantly different from their static counterparts. Inducing transition between them can turn on remarkable electronic phenomena, enriching our understanding of correlated electron systems as well as opening a window for potential applications in electronic devices

Constancy of the bilayer splitting as a function of doping in Bi2Sr2CaCu2O8+δBi_{2}Sr_{2}CaCu_{2}O_{8+δ}

Using high energy resolution angle resolved photoemission spectroscopy, we have resolved the bilayer splitting effect in a wide range of dopings of the bilayer cuprate $Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}$. This bilayer splitting is due to a nonvanishing intracell coupling $t_{\perp}$, and contrary to expectations, it is not reduced in the underdoped materials. This has implications for understanding the increased c-axis confinement in underdoped materials