Quasiparticle band structure and excitonic optical response in V 2 O 5 bulk and monolayer
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Garcia, Claudio (ORCID:0009000077503536)↗
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Results for “interlayer”
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Quantum-Well Bound States in Graphene Heterostructure Interfaces
We present experimental evidence of electronic and optical interlayer resonances in graphene van der Waals heterostructure interfaces. Using the spectroscopic mode of a low-energy electron microscope (LEEM), we characterized these interlayer resonant states up to 10 eV above the vacuum level. Compared with nontwisted, AB-stacked bilayer graphene (AB BLG), an ≈ 0.2 Å increase was found in the interlayer spacing of 30° twisted bilayer graphene (30°-tBLG). In addition, we used Raman spectroscopy to probe the inelastic light-matter interactions. A unique type of Fano resonance was found around the D and G modes of the graphene lattice vibrations. This anomalous, robust Fano resonance is a direct result of quantum confinement and the interplay between discrete phonon states and the excitonic continuum.
36 MATERIALS SCIENCE↗
Second-Order Josephson Effect in Excitonic Insulators
We show that in electron-hole bilayers with excitonic orders arising from conduction and valence bands formed by atomic orbitals that have different parities, nonzero interlayer tunneling leads to a second-order Josephson effect. This means the interlayer electrical current is related to the phase of the excitonic order parameter as J = J c sin 2θ instead of J = J c sin θ and that the system has two degenerate ground states at θ = 0, π that can be switched by an interlayer voltage pulse. When generalized to a three dimensional stack of alternating electron-hole planes or a two dimensional stack of chains, the ac Josephson effect implies that electric field pulses perpendicular to the layers and chains can steer the order parameter phase between the two degenerate ground states, making these devices ultrafast memories. Here, the order parameter steering also applies to the excitonic insulator candidate Ta 2 NiSe 5 .
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Hybridization of Bogoliubov Quasiparticles between Adjacent CuO 2 Layers in the Triple-Layer Cuprate Bi 2 Sr 2 Ca 2 Cu 3 O 10 + δ Studied by Angle-Resolved Photoemission Spectroscopy
Hybridization of Bogoliubov quasiparticles (BQPs) between the CuO 2 layers in the triple-layer cuprate high-temperature superconductor Bi 2 Sr 2 Cu 2 Cu 3 O 10+δ is studied by angle-resolved photoemission spectroscopy (ARPES). In the superconducting state, an anticrossing gap opens between the outer- and inner-BQP bands, which we attribute primarily to interlayer single-particle hopping with possible contributions from interlayer Cooper pairing. We find that the d-wave superconducting gap of both BQP bands smoothly develops with momentum without an abrupt jump in contrast to a previous ARPES study. Hybridization between the BQPs also gradually increases in going from the off nodal to the antinodal region, which is explained by the momentum dependence of the interlayer single-particle hopping. As possible mechanisms for the enhancement of the superconducting transition temperature, the hybridization between the BQPs as well as the combination of phonon modes of the triple CuO 2 layers and spin fluctuations represented by a four-well model are discussed.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
SU(4) Chiral Spin Liquid, Exciton Supersolid, and Electric Detection in Moiré Bilayers
We propose a moiré bilayer as a platform where exotic quantum phases can be stabilized and electrically detected. Moiré bilayers consist of two separate moiré superlattice layers coupled through the interlayer Coulomb repulsion. In the small distance limit, an SU(4) spin can be formed by combining layer pseudospin and the real spin. As a concrete example, we study an SU(4) spin model on triangular lattice in the fundamental representation. By tuning a three-site ring exchange term K ~ ( t 3 /U 2 ), we find the SU(4) symmetric crystallized phase and an SU (4) 1 chiral spin liquid at the balanced filling. We also predict two different exciton supersolid phases with interlayer coherence at imbalanced filling under displacement field. Especially, the system can simulate an SU(2) Bose-Einstein condensation by injecting interlayer excitons into the magnetically ordered Mott insulator at the layer polarized limit. Smoking gun evidences of these phases can be obtained by measuring the pseudospin transport in the counterflow channel.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Superconductivity from Domain Wall Fluctuations in Sliding Ferroelectrics
Bilayers of two-dimensional van der Waals materials that lack an inversion center can show a novel form of ferroelectricity, where certain stacking arrangements of the two layers lead to an interlayer polarization. Under an external out-of-plane electric field, a relative sliding between the two layers can occur, accompanied by an interlayer charge transfer and a ferroelectric switching. We show that the domain walls that mediate ferroelectric switching are a locus of strong attractive interactions between electrons. The attraction is mediated by the ferroelectric domain wall fluctuations, effectively driven by the soft interlayer shear phonon. We comment on the possible relevance of this attraction mechanism to the recent observation of an interplay between sliding ferroelectricity and superconductivity in bilayer T 𝑑 −MoTe 2 . We also discuss the possible role of this mechanism in the superconductivity of moiré bilayers.
Chaudhary, Gaurav [Univ. of Cambridge (United King↗
CrI 3 revisited with a many-body ab initio theoretical approach
CrI 3 has recently been shown to exhibit low-dimensional, long-range magnetic ordering from few layers to single layers of CrI 3 . The properties of CrI 3 bulk and few layered systems are uniquely defined by a combination of short-range intralayer and long-range interlayer interactions; including strong correlations, exchange and spin orbit coupling. Unfortunately, both the long-range van der Waals interactions, which are driven by dynamic, many-body electronic correlations and the competing strong intralayer correlations, present a formidable challenging for the local or semi local mean-field approximations employed in workhorse electronic structure approaches like density functional theory. In this work, we employ a sophisticated many-body approach that can simultaneously describe long- and short-range correlations. Herein, we establish that the fixed-node diffusion Monte Carlo (FNDMC) method reproduces the experimental interlayer separation distance of bulk CrI 3 for the high-temperature, monoclinic phase, with a reliable prediction of the interlayer binding energy. We subsequently employed, the FNDMC results to benchmark the accuracy of several density functional theory exchange-correlation approximations.
36 MATERIALS SCIENCE↗
Low-Temperature Competing Magnetic Energy Scales in the Topological Ferrimagnet TbMn 6 Sn 6
TbMn 6 Sn 6 is a metallic ferrimagnet displaying signatures of both topological electrons and topological magnons arising from ferromagnetism and spin-orbit coupling within its Mn kagome layers. Inelastic neutron scattering measurements find strong ferromagnetic (FM) interactions within the Mn kagome layer and reveal a magnetic bandwidth of ~230 meV. The low-energy magnetic excitations are characterized by strong FM Mn-Mn and antiferromagnetic (AFM) Mn-Tb interlayer magnetic couplings. We observe weaker, competing long-range FM and AFM Mn-Mn interlayer interactions similar to those driving helical magnetism in the YMn 6 Sn 6 system. Combined with density-functional theory calculations, we find that competing Mn-Mn interlayer magnetic interactions occur in all RMn 6 Sn 6 compounds with R=Y, Gd-Lu, resulting in magnetic instabilities and tunability when Mn-R interactions are weak. In the case of TbMn 6 Sn 6 , strong AFM Mn-Tb coupling ensures a highly stable three-dimensional ferrimagnetic network.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Collective Modes in Multilayer Graphene/𝛼−RuCl 3 Heterostructures
Collective modes in multilayer graphene, such as plasmons and phonons, exhibit sensitivity to displacement fields and interlayer coupling, distinguishing them from their counterparts in single-layer graphene. Here, we engineer collective modes in charge-transfer heterostructures composed of multilayer graphene and 𝛼−RuCl 3 . In heterostructures with a single 𝛼−RuCl 3 interface, the charge transfer generates displacement fields up to 7 V/nm at the interface between 𝛼−RuCl 3 and the adjacent graphene layer—the highest value achieved through charge-transfer methods. As a result of the broken inversion symmetry, we discover enhanced nonlinear optical response and modified phonon selection rules. Conversely, we find that multilayer graphene sandwiched between two 𝛼−RuCl 3 flakes causes displacement fields to cancel. There, we achieve carrier densities as high as 8 ×10 13 cm −2 in multilayer graphene and restore the phonon selection rules to their unperturbed state. Meanwhile, we demonstrate that plasmonic properties derive from the depletion of multiple valence bands. As a result of the quasilinear band dispersion, these “Dirac multiband plasmons” are relatively unaffected by displacement fields. On the other hand, the inverted heterostructure sequence—two multilayer graphene sheets encapsulating 𝛼−RuCl 3 —activates significant alteration of the plasmons via interlayer plasmon-plasmon coupling. Hence, multilayer graphene and 𝛼−RuCl 3 heterostructures offer a gate-free platform for engineering collective modes derived from inversion symmetry and interlayer coupling.
Moore, Samuel L. [Columbia University, New York, N↗
Competing magnetic phases in Li-Fe-Ge kagome systems
Competing interlayer magnetic interactions in kagome magnets can lead to diverse magnetic phases, which enable promising topological or quantum material properties. In this work, the electronic structure and magnetic properties are studied using first-principles calculations for the LiFe6Ge6, LiFe6Ge4, and LiFe6Ge5 compounds sharing the kagome Fe3Ge layer motif but with different interlayer arrangements. For LiFe6Ge4 and LiFe6Ge5, the predicted magnetic ground states are collinear antiferromagnetic (AFM) states involving a mix of ferromagnetic (FM) and AFM interlayer orientations. In contrast, for LiFe6Ge6, an incommensurate cycloidal spin spiral ground state is stabilized, although its energy is close to a collinear A-type AFM state. The analysis of magnetic RKKY exchange coupling confirms the results of calculations. The values of atomic magnetic moments are in good agreement with existing experimental estimations. Our experiments on LiFe6Ge6 single crystals reveals AFM ordering at ∼540 K and transition to another magnetic phase with a small FM component, possibly with spin canting, below ∼270 K.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Spin Stripes and Superconductivity in Bilayer Nickelates
The bilayer nickelate La3Ni2O7 has recently emerged as a high-temperature superconductor with unusual spin stripe order in its ambient pressure phase. We propose a microscopic Hamiltonian that faithfully reflects the crystalline symmetry of this system, with the primary aim of addressing its unconventional magnetism at ambient pressure. Using state-of-the-art density matrix renormalization group calculations, we show that (π/2,π/2) spin stripe order arises in our model at sizable Hund's coupling JH from a hidden quasi-one-dimensionality and persists over a range of electron concentrations. In the more symmetric high-pressure regime, our model exhibits enhanced interlayer pairing tendencies when the interlayer antiferromagnetic coupling J⊥ becomes sufficiently large. Our results provide a microscopic origin of the diagonal spin stripes and identify Hund's coupling JH and interlayer coupling J⊥ as key ingredients governing magnetic order and pairing tendencies in La3Ni2O7.
Wang, Hao-Xin [The Chinese University of Hong Kong↗
Emergent Halperin–Saslow mode, gauge glass and quenched disorders in quantum Ising magnet TmMgGaO 4
Quenched disorders could bring novel quantum excitations and models to certain quantum magnets. Motivated by recent experiments on the quantum Ising magnet TmMgGaO 4 , we explore the effects of the quenched disorder and the interlayer coupling in this triangular lattice Ising antiferromagnet. It is pointed out that the weak quenched (nonmagnetic) disorder would convert the emergent 2D Berezinskii–Kosterlitz–Thouless (BKT) phase and the critical region into a U(1) gauge glass. There will be an emergent Halperin–Saslow mode associated with this gauge glass. Using the Imry-Ma’s renormalization group result, we explain the fate of the finite-field [Formula: see text] symmetry breaking transition at the low temperatures. The ferromagnetic interlayer coupling would suppress the BKT phase and generate a tiny ferromagnetism. With quenched disorders, this interlayer coupling changes the 2D gauge glass into a 3D gauge glass, and the Halperin–Saslow mode persists. This work merely focuses on addressing a phase regime in terms of emergent U(1) gauge glass behaviors and hope to inspire future works and thoughts in weakly disordered frustrated magnets in general.
Physics↗
All Solid-State Li/LLZO/LCO Battery Enabled by Alumina Interfacial Coating
Li 7 La 3 Zr 2 O 12 (LLZO) garnet-type lithium-ion conductors are being investigated as a promising solid electrolyte for solid-state lithium batteries. To enable a functional all-solid-state configuration intensive investigations are needed to reduce the cathode/electrolyte interfacial resistance which contributes the most to cell performance loss. Among the commercial cathode materials investigated so far, LiCoO 2 (LCO) is one of the most stable with garnet electrolytes as only a superficial reaction has been detected between the two materials. However, even this minor reaction would block the Li-ion transport through the interface, resulting in deteriorated cell performance. In this work, we demonstrate that a thin aluminum oxide layer (5 nm) can be an effective interlayer to impede the formation of a harmful interphase and enable facile Li-ion transfer between LCO and the LLZO garnet. Room-temperature-sputtered LCO thin films were employed to form an interface with the garnet electrolyte and annealed at 800 °C to reveal the effect of the interfacial reaction on the Li-ion transfer across the interface. An aluminum oxide layer was then introduced between LCO and the garnet electrolyte by sputtering a metallic aluminum layer which is then annealed together with the upper LCO layer in oxygen, or by direct atomic layer deposition of the oxide. Compared to the LCO/LLZO/Li cells without an aluminum oxide interlayer, those with the interlayer exhibited improved performance, i.e., a stable discharge capacity of up to 90 mAh/(g LCO) at a C/10 rate, a rate capability up to 1.68C and a stable galvanostatic cycling at 0.1C for over 100 cycles with a discharge capacity fade rate of 0.15% per cycle. It was determined that aluminum diffused into the LCO layer after preventing the initial detrimental reaction between LCO and the LLZO garnet from happening during high temperature annealing, suggesting that the coating does not have to remain a physically blocking layer during cycling to function.
Electrochemistry↗
Investigation of mechanochemical interactions of hydrogen with earth materials in a subsurface gas storage
The goal of this project is to investigate the molecular interactions of H 2 with earth materials (EMs) that may potentially affect economics and safety of H 2 geological storage (HGS). We investigated (1) the H 2 intercalation into interlayers of phyllosilicates, (2) the competitive adsorption of H 2 /CH 4 onto porous materials, and (3) solubility of H 2 in interfacial and confined hydrocarbons. Our results indicate that (i) H 2 intercalation into hydrated interlayers is thermodynamically unfavorable and H 2 solubility in hydrated clay interlayers is in the same order of magnitude as that in bulk water, (ii) CH 4 outcompetes H 2 in adsorption onto kerogen, due to stronger CH 4 -kerogen interactions than H 2 -kerogen interactions, (iii) H 2 tends to dissolve more in oil than in water, and the introduction of CO 2 as a cushion gas reduces H 2 partitioning near the kaolinite surfaces. The outcomes provide foundational knowledge for preparing the USA for future storage site selection and storage system design, supporting DOE missions in clean and secured energy.
08 HYDROGEN↗
Interaction between clay minerals and organics in asteroid Ryugu
The Hayabusa 2 spacecraft brought back to Earth grains of the carbonaceous asteroid Ryugu. Such grains represent the pristine state of CI chondritic materials and have been preserved from exposure to Earth’s atmosphere. Here, we show evidence of the presence of organics trapped within the interlayer space of smectite layers in Ryugu grains. No such organics are found in the Orgueil CI meteorite. We put forward that the organics within the interlayer space of smectite in Orgueil CI meteorite were lost during their oxidation on Earth. Also, we propose that the presence of organics within the interlayers space of smectite might be responsible for the possible NH infrared signature observed in Ryugu particles and potentially to a few large C-type asteroids including Ceres
58 GEOSCIENCES↗
Bulk direct gap MoS2 by plasma induced layer decoupling
Bulk direct transition metal dichalcogenide (TMDC) may have an increased interlayer separation of at least 0.5, 1, or 3 angstroms more than its bulk value. The TMDC may be a bulk direct band gap molybdenum disulfide (MoS2) or a bulk direct band gap tungsten diselenide (WSe2). Oxygen may be between the interlayers. A device may include the TMDC, such as an optoelectronic device, such as an LED, solid state laser, a photodetector, a solar cell, a FET, a thermoelectric generator, or a thermoelectric cooler. A method of making bulk direct transition metal dichalcogenide (TMDC) with increased interlayer separation may include exposing bulk direct TMDC to a remote (aka downstream) oxygen plasma. The plasma exposure may cause an increase in the photoluminescence efficiency of the TMDC, more charge neutral doping, or longer photo-excited carrier lifetimes, as compared to the TMDC without the plasma exposure.
36 MATERIALS SCIENCE↗
Energy storage technology with extreme high energy density capability
A capacitor includes a first electrode having a substrate and a plurality of nanostructures physically and electrically coupled to the substrate. The capacitor also includes a solid, non-conductive interlayer deposited over the nanostructures to coat the nanostructures, and extending between the nanostructures, and a second electrode deposited over the interlayer and extending between the nanostructures. The interlayer insulates the first and second electrode layers from one another.
Gao, Kaizhong↗
Dual material fused filament fabrication of composite core‐shell structures with improved impact resistance and interfacial adhesion
The mechanical performance of parts produced by fused filament fabrication (FFF) has been limited due to the presence of voids and poor interlayer welding. Recent advancements in FFF have enabled the fabrication of void-free objects with strong interlayer welding through the use of semicrystalline polymer shells such as high-density polyethylene (HDPE) along with a high viscosity core polymer like acrylonitrile-butadiene-styrene (ABS). Furthermore, the zero-shear viscosity (η0) of ABS is three orders of magnitude higher than HDPE making the ABS-HDPE core-shell configuration preferable. ABS holds the shape by preventing bulk flow and part bending while HDPE promotes full surface contact across the layers. Most polymers, however, are immiscible which causes a weak weld line along the core-shell interface. Herein, maleic anhydride (MAH) is grafted to the butadiene segment of the ABS core thereby compatibilizing the interface with HDPE, improving the interfacial adhesion. Attenuated total reflectance-Fourier transform infrared spectroscopy was employed to confirm successful grafting. Using a custom-made die affording the core-shell structure, the ABS-g-MAH is shown to improve the impact resistance by 253% and 16% compared to neat HDPE and ABS specimens, respectively. Additionally, a 10% increase compared to the unmodified ABS-HDPE core-shell configuration is observed.
36 MATERIALS SCIENCE↗