Discovery of giant unit-cell super-structure in the infinite-layer nickelate PrNiO.

The discovery of unconventional superconductivity often triggers significant interest in associated electronic and structural symmetry breaking phenomena. For the infinite-layer nickelates, structural allotropes are investigated intensively. Here, using high-energy grazing-incidence x-ray diffraction, we demonstrate how in-situ temperature annealing of the infinite-layer nickelate PrNiO ( ≈ 0) induces a giant superlattice structure.

Magnetic excitations in strained infinite-layer nickelate PrNiO films.

Strongly correlated materials respond sensitively to external perturbations such as strain, pressure, and doping. In the recently discovered superconducting infinite-layer nickelates, the superconducting transition temperature can be enhanced via only ~ 1% compressive strain-tuning with the root of such enhancement still being elusive. Using resonant inelastic x-ray scattering (RIXS), we investigate the magnetic excitations in infinite-layer PrNiO thin films grown on two different substrates, namely SrTiO (STO) and (LaAlO)(SrTaAlO) (LSAT) enforcing different strain on the nickelates films.

Magnon interactions in a moderately correlated Mott insulator.

Quantum fluctuations in low-dimensional systems and near quantum phase transitions have significant influences on material properties. Yet, it is difficult to experimentally gauge the strength and importance of quantum fluctuations. Here we provide a resonant inelastic x-ray scattering study of magnon excitations in Mott insulating cuprates.

Weak signal extraction enabled by deep neural network denoising of diffraction data.

The removal or cancellation of noise has wide-spread applications in imaging and acoustics. In applications in everyday life, such as image restoration, denoising may even include generative aspects, which are unfaithful to the ground truth. For scientific use, however, denoising must reproduce the ground truth accurately.

Fate of charge order in overdoped La-based cuprates.

In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with a commensuration of eight and four lattice units, respectively. How this stripe order evolves across optimal doping remains a controversial question. Here we present a systematic resonant inelastic x-ray scattering study of weak charge correlations in LaSrCuO and LaEuSrCuO.

Field-tuned quantum effects in a triangular-lattice Ising magnet.

We report thermodynamic and neutron scattering measurements of the triangular-lattice quantum Ising magnet TmMgGaO in longitudinal magnetic fields. Our experiments reveal a quasi-plateau state induced by quantum fluctuations. This state exhibits an unconventional non-monotonic field and temperature dependence of the magnetic order and excitation gap.

Anomalous Contribution to the Nematic Electronic States from the Structural Transition in FeSe Revealed by Time- and Angle-Resolved Photoemission Spectroscopy.

High-resolution time- and angle-resolved photoemission measurements were made on FeSe superconductors. With ultrafast photoexcitation, two critical excitation fluences that correspond to two ultrafast electronic phase transitions were found only in the d_{yz}-orbit-derived band near the Brillouin-zone center within our time and energy resolution. Upon comparison to the detailed temperature dependent measurements, we conclude that there are two equilibrium electronic phase transitions (at approximately 90 and 120 K) above the superconducting transition temperature, and an anomalous contribution on the scale of 10 meV to the nematic states from the structural transition is experimentally determined.

Resonant inelastic soft x-ray scattering on LaPtSi.

X-ray absorption and resonant inelastic x-ray scattering spectra of LaPtSisingle crystal at the Si 2and La 4edges are presented. The data are interpreted in terms of density functional theory, showing that the Si spectra can be described in terms of Siandlocal partial density of states (LPDOS), and the La spectra are due to quasi-atomic local 4excitations. Calculations show that Pt-LPDOS dominates the occupied states, and a sharp localized Lastate is found in the unoccupied states, in line with the observations.

Uniaxial pressure induced stripe order rotation in LaSrCuO.

Static stripe order is detrimental to superconductivity. Yet, it has been proposed that transverse stripe fluctuations may enhance the inter-stripe Josephson coupling and thus promote superconductivity. Direct experimental studies of stripe dynamics, however, remain difficult.

A computer based facial flaps simulator using projective dynamics.

Background And Objectives: Interactive surgical simulation using the finite element method to model human skin mechanics has been an elusive goal. Mass-spring networks, while fast, do not provide the required accuracy.

Methods: This paper presents an interactive, cognitive, facial flaps simulator based on a projective dynamics computational framework.

Long-Term Results of the Murawski Unilateral Cleft Lip Repair.

Background: In 1968, Ralph Millard published his "Millard II" method for repair of wide, complete unilateral cleft lip and nose deformity. In 1979, Murawski published a major modification of the Millard II procedure in Polish. This motif was taken up 8 years later by Mohler and 22 years later by Cutting.

Polarized neutron scattering studies of magnetic excitations in iron-selenide superconductor LiFeODFeSe (41 K).

We report polarized neutron scattering measurements of the low energy spin fluctuations of the iron-selenide superconductor LiFeODFeSe below and above its superconducting transition temperature= 41 K. Our experiments confirmed that the resonance mode near 21 meV is magnetic. Moreover, the spin excitations are essentially isotropic in spin space at 5 ⩽⩽ 29 meV in the superconducting and normal states.

Charge order lock-in by electron-phonon coupling in LaEuSrCuO.

Charge order is universal to all hole-doped cuprates. Yet, the driving interactions remain an unsolved problem. Electron-electron interaction is widely believed to be essential, whereas the role of electron-phonon interaction is unclear.

Evolution of spin excitations from bulk to monolayer FeSe.

In ultrathin films of FeSe grown on SrTiO (FeSe/STO), the superconducting transition temperature T is increased by almost an order of magnitude, raising questions on the pairing mechanism. As in other superconductors, antiferromagnetic spin fluctuations have been proposed to mediate SC making it essential to study the evolution of the spin dynamics of FeSe from the bulk to the ultrathin limit. Here, we investigate the spin excitations in bulk and monolayer FeSe/STO using resonant inelastic x-ray scattering (RIXS) and quantum Monte Carlo (QMC) calculations.

Observation of an electronic order along [110] direction in FeSe.

Multiple ordered states have been observed in unconventional superconductors. Here, we apply scanning tunneling microscopy to probe the intrinsic ordered states in FeSe, the structurally simplest iron-based superconductor. Besides the well-known nematic order along [100] direction, we observe a checkerboard charge order in the iron lattice, which we name a [110] electronic order in FeSe.

High-Temperature Charge-Stripe Correlations in La_{1.675}Eu_{0.2}Sr_{0.125}CuO_{4}.

We use resonant inelastic x-ray scattering to investigate charge-stripe correlations in La_{1.675}Eu_{0.2}Sr_{0.

Coexistence of Ferromagnetic and Stripe-Type Antiferromagnetic Spin Fluctuations in YFe_{2}Ge_{2}.

We report neutron scattering measurements of single-crystalline YFe_{2}Ge_{2} in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe_{2}Ge_{2} does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe_{2}Ge_{2} displays anisotropic stripe-type antiferromagnetic spin fluctuations at (π, 0, π).

Structure of spin excitations in heavily electron-doped LiFeODFeSe superconductors.

Heavily electron-doped iron-selenide high-transition-temperature (high-T ) superconductors, which have no hole Fermi pockets, but have a notably high T , have challenged the prevailing s pairing scenario originally proposed for iron pnictides containing both electron and hole pockets. The microscopic mechanism underlying the enhanced superconductivity in heavily electron-doped iron-selenide remains unclear. Here, we used neutron scattering to study the spin excitations of the heavily electron-doped iron-selenide material LiFeODFeSe (T  = 41 K).

Evidence for a spinon Fermi surface in a triangular-lattice quantum-spin-liquid candidate.

A quantum spin liquid is an exotic quantum state of matter in which spins are highly entangled and remain disordered down to zero temperature. Such a state of matter is potentially relevant to high-temperature superconductivity and quantum-information applications, and experimental identification of a quantum spin liquid state is of fundamental importance for our understanding of quantum matter. Theoretical studies have proposed various quantum-spin-liquid ground states, most of which are characterized by exotic spin excitations with fractional quantum numbers (termed 'spinons').

Magnetic ground state of FeSe.

Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated.

Transition from Sign-Reversed to Sign-Preserved Cooper-Pairing Symmetry in Sulfur-Doped Iron Selenide Superconductors.

An essential step toward elucidating the mechanism of superconductivity is to determine the sign or phase of the superconducting order parameter, as it is closely related to the pairing interaction. In conventional superconductors, the electron-phonon interaction induces attraction between electrons near the Fermi energy and results in a sign-preserved s-wave pairing. For high-temperature superconductors, including cuprates and iron-based superconductors, prevalent weak coupling theories suggest that the electron pairing is mediated by spin fluctuations which lead to repulsive interactions, and therefore that a sign-reversed pairing with an s_{±} or d-wave symmetry is favored.

Strong interplay between stripe spin fluctuations, nematicity and superconductivity in FeSe.

In iron-based superconductors the interactions driving the nematic order (that breaks four-fold rotational symmetry in the iron plane) may also mediate the Cooper pairing. The experimental determination of these interactions, which are believed to depend on the orbital or the spin degrees of freedom, is challenging because nematic order occurs at, or slightly above, the ordering temperature of a stripe magnetic phase. Here, we study FeSe (ref.

Landau level splitting in Cd3As2 under high magnetic fields.

Three-dimensional topological Dirac semimetals (TDSs) are a new kind of Dirac materials that exhibit linear energy dispersion in the bulk and can be viewed as three-dimensional graphene. It has been proposed that TDSs can be driven to other exotic phases like Weyl semimetals, topological insulators and topological superconductors by breaking certain symmetries. Here we report the first transport experiment on Landau level splitting in TDS Cd3As2 single crystals under high magnetic fields, suggesting the removal of spin degeneracy by breaking time reversal symmetry.