Strange metallicity in the doped Hubbard model Huang, Edwin W; Sheppard, Ryan; Moritz, Brian ...
Science (American Association for the Advancement of Science),
11/2019, Volume:
366, Issue:
6468
Journal Article
Peer reviewed
Open access
Strange or bad metallic transport, defined by incompatibility with the conventional quasiparticle picture, is a theme common to many strongly correlated materials, including high-temperature ...superconductors. The Hubbard model represents a minimal starting point for modeling strongly correlated systems. Here we demonstrate strange metallic transport in the doped two-dimensional Hubbard model using determinantal quantum Monte Carlo calculations. Over a wide range of doping, we observe resistivities exceeding the Mott-Ioffe-Regel limit with linear temperature dependence. The temperatures of our calculations extend to as low as 1/40 of the noninteracting bandwidth, placing our findings in the degenerate regime relevant to experimental observations of strange metallicity. Our results provide a foundation for connecting theories of strange metals to models of strongly correlated materials.
The search for quantum spin liquids in frustrated quantum magnets recently has enjoyed a surge of interest, with various candidate materials under intense scrutiny. However, an experimental ...confirmation of a gapped topological spin liquid remains an open question. Here, we show that circularly polarized light can provide a knob to drive frustrated Mott insulators into a chiral spin liquid, realizing an elusive quantum spin liquid with topological order. We find that the dynamics of a driven Kagome Mott insulator is well-captured by an effective Floquet spin model, with heating strongly suppressed, inducing a scalar spin chirality S
· (S
× S
) term which dynamically breaks time-reversal while preserving SU(2) spin symmetry. We fingerprint the transient phase diagram and find a stable photo-induced chiral spin liquid near the equilibrium state. The results presented suggest employing dynamical symmetry breaking to engineer quantum spin liquids and access elusive phase transitions that are not readily accessible in equilibrium.
Monolayer transition-metal dichalcogenides are novel materials which at low energies constitute a condensed-matter realization of massive relativistic fermions in two dimensions. Here, we show that ...this picture breaks for optical pumping-instead, the added complexity of a realistic materials description leads to a new mechanism to optically induce topologically protected chiral edge modes, facilitating optically switchable conduction channels that are insensitive to disorder. In contrast to graphene and previously discussed toy models, the underlying mechanism relies on the intrinsic three-band nature of transition-metal dichalcogenide monolayers near the band edges. Photo-induced band inversions scale linearly in applied pump field and exhibit transitions from one to two chiral edge modes on sweeping from red to blue detuning. We develop an ab initio strategy to understand non-equilibrium Floquet-Bloch bands and topological transitions, and illustrate for WS
that control of chiral edge modes can be dictated solely from symmetry principles and is not qualitatively sensitive to microscopic materials details.
The recent discovery of superconductivity in oxygen-reduced monovalent nickelates has raised a new platform for the study of unconventional superconductivity, with similarities to and differences ...from the cuprate high-temperature superconductors. In this paper, we investigate the family of infinite-layer nickelatesRNiO2with rare-earthRspanning across the lanthanide series, introducing a new and nontrivial “knob” with which to tune nickelate superconductivity. When traversing from La to Lu, the out-of-plane lattice constant decreases dramatically with an accompanying increase of Nidx2−y2bandwidth; however, surprisingly, the role of oxygen charge transfer diminishes. In contrast, the magnetic exchange grows across the lanthanides, which may be favorable to superconductivity. Moreover, compensation effects from the itinerant5delectrons present a closer analogy to Kondo lattices, indicating a stronger interplay between charge transfer, bandwidth renormalization, compensation, and magnetic exchange. We also obtain the microscopic Hamiltonian using the Wannier downfolding technique, which will provide the starting point for further many-body theoretical studies.
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Despite significant progress in resonant inelastic x-ray scattering (RIXS) experiments on cuprates at the Cu L -edge, a theoretical understanding of the cross section remains incomplete in terms of ...elementary excitations and the connection to both charge and spin structure factors. Here, we use state-of-the-art, unbiased numerical calculations to study the low-energy excitations probed by RIXS in the Hubbard model, relevant to the cuprates. The results highlight the importance of scattering geometry, in particular, both the incident and scattered x-ray photon polarization, and they demonstrate that on a qualitative level the RIXS spectral shape in the cross-polarized channel approximates that of the spin dynamical structure factor. However, in the parallel-polarized channel, the complexity of the RIXS process beyond a simple two-particle response complicates the analysis and demonstrates that approximations and expansions that attempt to relate RIXS to less complex correlation functions cannot reproduce the full diversity of RIXS spectral features.
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The appearance of certain spectral features in one-dimensional (1D) cuprate materials has been attributed to a strong, extended attractive coupling between electrons. Here, using time-dependent ...density matrix renormalization group methods on a Hubbard-extended Holstein model, we show that extended electron-phonon (e-ph) coupling presents an obvious choice to produce such an attractive interaction that reproduces the observed spectral features and doping dependence seen in angle-resolved photoemission experiments: diminished 3k
spectral weight, prominent spectral intensity of a holon-folding branch, and the correct holon band width. While extended e-ph coupling does not qualitatively alter the ground state of the 1D system compared to the Hubbard model, it quantitatively enhances the long-range superconducting correlations and suppresses spin correlations. Such an extended e-ph interaction may be an important missing ingredient in describing the physics of the structurally similar two-dimensional high-temperature superconducting layered cuprates, which may tip the balance between intertwined orders in favor of uniform d-wave superconductivity.
To shed light on the formation process and structure of the solid electrolyte interphase (SEI) layer on native oxide-terminated silicon wafer anodes from a carbonate-based electrolyte (LP30), we ...combined in situ synchrotron X-ray reflectivity, linear sweep voltammetry, ex situ X-ray photoelectron spectroscopy, and first principles calculations from the Materials Project. We present in situ sub-nanometer resolution structural insights and compositional information of the SEI, as well as predicted equilibrium phase stability. Combining these findings, we observe two well-defined inorganic SEI layers next to the Si anode—a bottom-SEI layer (adjacent to the electrode) formed via the lithiation of the native oxide, and a top-SEI layer mainly consisting of the electrolyte decomposition product LiF. Our study provides novel mechanistic insights into the SEI growth process on Si, and we discuss several important implications regarding ion and electron transport through the SEI layer.
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•Multi-property study of the structure and composition of the SEI•Potential-dependent growth of two well-defined inorganic SEI layers on Si/SiO2 anode•Unraveling of Li+ and e− transport properties through the SEI
Despite the electronic revolution initiated by lithium-ion batteries (LIBs) three decades ago, one aspect of these energy storage devices still puzzles researchers. This is the solid electrolyte interphase (SEI) that forms on electrodes because LIBs operate outside the electrolyte stability window and can effectively passivate the electrode. Experimentally, the SEI is challenging to study with the desired atomic resolution as it is buried at the electrolyte-electrode interface.
In this article, we provide fresh insights into the nature and transport properties of the SEI, via a multi-property combined experimental and simulation approach utilizing well-defined model systems. We unraveled the structure and composition, as well as the formation mechanism of the SEI on silicon anodes. Our findings are discussed with regard to understanding possible SEI-induced bottlenecks in LIBs and the relevance for their optimization.
The solid electrolyte interphase (SEI) is a passivation layer naturally formed on battery electrodes. It protects electrodes and electrolytes from degradation and dictates charging time capabilities and lifetime. Despite its importance, it remains a poorly understood battery component. This study provides novel insights into the formation, morphology, and composition of the SEI on Si anodes through a multi-modal approach. The findings show a layered SEI and the ion and electron conductivities, as well as their relation to performance, are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Nematicity, defined as broken rotational symmetry, has recently been observed in competing phases proximate to the superconducting phase in the cuprate high-temperature superconductors. Similarly, ...the new iron-based high-temperature superconductors exhibit a tetragonal-to-orthorhombic structural transition (i.e., a broken C₄ symmetry) that either precedes or is coincident with a collinear spin density wave (SDW) transition in undoped parent compounds, and superconductivity arises when both transitions are suppressed via doping. Evidence for strong in-plane anisotropy in the SDW state in this family of compounds has been reported by neutron scattering, scanning tunneling microscopy, and transport measurements. Here, we present an angle-resolved photoemission spectroscopy study of detwinned single crystals of a representative family of electron-doped iron-arsenide superconductors, Ba(Fe1-xCox)₂As₂ in the underdoped region. The crystals were detwinned via application of in-plane uniaxial stress, enabling measurements of single domain electronic structure in the orthorhombic state. At low temperatures, our results clearly demonstrate an in-plane electronic anisotropy characterized by a large energy splitting of two orthogonal bands with dominant dxz and dyz character, which is consistent with anisotropy observed by other probes. For compositions x > 0, for which the structural transition (Ts) precedes the magnetic transition (TSDW), an anisotropic splitting is observed to develop above TSDW, indicating that it is specifically associated with TS. For unstressed crystals, the band splitting is observed close to Ts. whereas for stressed crystals, the splitting is observed to considerably higher temperatures, revealing the presence of a surprisingly large in-plane nematic susceptibility in the electronic structure.
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Recent debates on the oxygen redox behaviors in battery electrodes have triggered a pressing demand for the reliable detection and understanding of nondivalent oxygen states beyond conventional ...absorption spectroscopy. Here, enabled by high-efficiency mapping of resonant inelastic X-ray scattering (mRIXS) coupled with first-principles calculations, we report distinct mRIXS features of the oxygen states in Li2O, Li2CO3, and especially, Li2O2, which are successfully reproduced and interpreted theoretically. mRIXS signals are dominated by valence-band decays in Li2O and Li2CO3. However, the oxidized oxygen in Li2O2 leads to partially unoccupied O-2p states that yield a specific intraband excitonic feature in mRIXS. Such a feature displays a specific emission energy in mRIXS, which disentangles the oxidized oxygen states from the dominating transition-metal/oxygen hybridization features in absorption spectroscopy, thus providing critical hints for both detecting and understanding the oxygen redox reactions in transition-metal oxide based battery materials.
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