The Dy3+ ions doped tungsten gadolinium borate (Dy-WGdB) glasses were synthesis by the melt-quenching technique with various Dy2O3 concentrations. The physics, optical and several types of luminescence properties in the Dy-WGdB glass samples were researched. Glass densities (∼6.0 g/cm3) indicates that the compaction of glass is high and rise with an increment of Dy2O3 concentrations. The Dy-WGdB glass samples absorb photons in visible light (VIS) and near-infrared (NIR) region from the absorption spectra. For photo-, radio- and proton luminescence, the highest emission was observed at 575 nm, corresponding to Dy3+ transition 4F9/2→6H13/2. The maximum concentration of Dy2O3 doped in the WGdB glass is 1.0 mol%, which has achieved the highest emission intensity in all three types of luminescence. For 1.0 mol% doped glass, the decay times under pulse X-ray excitation was measured and found to be 0.216 ms. The temperature dependent luminescence spectra of the 1.0 % doped glass in a temperature range, 10 K – 300 K was measured and found the thermal quenching. In this research, under the photo, X-ray and proton excitation, the WGdB glass doped with Dy2O3 displays the strong luminescence in the VIS region. It has the potential for applications in high-energy and nuclear physics, radiation control and homeland security.

The ab initio projector augmented wave method of the density functional theory is applied for studying energy characteristics of oxygen vacancies and migration pathways in Pr1−xYxBaCo2O6−δ. It is found that the negative formation energy leads to initial appearance of oxygen vacancies in PrO planes thus providing the pathway for oxygen migration at small δ's. The increase of oxygen vacancy population in PrO planes and replacement of Pr by Y both favor a weakening of CoO bonds, which facilitates the increase in the amount of oxygen vacancies in CoO2 layers. Moreover, the yttrium dopants enlarge the bottleneck for oxygen jumps along ⟨101⟩ directions over oxygen vacancies in PrO and CoO2 layers. As a result, the respective ‘zigzag’ oxygen migration pathway becomes predominant with increasing oxygen non-stoichiometry and yttrium doping. Thus, the layered perovskite-like cobaltites give an example of a peculiar diffusion process where minority defects provide the transport channel while majority defects maintain favorable geometry of the migration pathway.

The global research efforts for identification of electrode materials for high energy and high power density rechargeable aqueous/non-aqueous aluminum-ion batteries have gained unprecedented momentum in contemporary times. Herein, we exclusively report the Al3+ ion electrochemistry of Bi2O3 in aqueous electrolyte for the first time. While investigating the electrochemical performance of Bi2O3, we demonstrate a unique method to simultaneously enhance the storage capacity and long-term stability of Bi2O3 as an electrode material for rechargeable aqueous aluminum-ion battery. It is found that a binder free integrated electrode of Bi2O3 on an exfoliated graphite current collector is better suited for improved electrochemical activity. When assembled with an Al metal anode, the integrated Bi2O3 electrode delivers a stable specific capacity of 103 mAhg−1 at a current rate of 1.5 Ag−1 over several charge/discharge cycles.

Using density functional theory calculations, the structural and electronic properties of the melt-castable energetic materials of bis-oxadiazole-bis-methylene dinitrate (BODN) were studied. The calculated lattice parameters, molecular geometry and band gap by the semi-empirical dispersion (Grimme) corrected generalized gradient approximation functional of Perdew-Burke-Ernzerhof (GGA-PBE-G06) are in good agreement with experimental and theoretical results. Also, the pressure effect on BODN was studied in this work. It is found that although the calculated lattice parameters a, b and c are all decreased monotonically with pressure up to 25 GPa, the b-axis is the easiest compressible. The compression behaviors of geometry were investigated, and found the bond C1-N1 and C3-O2 respective in the oxadiazole and alkyl nitric ester groups were more compressible than the others. The molecular interactions were examined by the Hirshfeld surface and 2D-fingerprint analysis. Moreover, the predicted band gap under high-pressure conditions was discussed as well.

In this paper, photoresistive properties in pristine and homogeneously boron and nitrogen doped semiconducting single-walled carbon nanotubes is studied. The calculations are based on density function theory in combination with Non-Equilibrium Greens Function formalism. The resistance in the SWCNT models is found to decrease with the increasing flux levels. At low electrode voltages, nitrogen doped model shows more photoresistive effect while at high electrode voltages, the most significant photoresistive effect is found in boron doped model. The study reveals that the resistance of the proposed SWCNT systems is dependent on the light intensity, and the conventional boron and nitrogen doping increases the photoresistance by manifold. The models are promising for wide range of applications in the future electronic industry.

A ferrimagnetic mixed spin square Blume-Capel Ising nanowire system on spin-1 core and spin-3/2 outer shell have been investigated. The general formula for the temperature dependence of the equilibrium magnetization of the system is presented. The ferrimagnetic core-shell nanosystem shows a compensation point when the exchange interactions are changed for different values of the single-ion anisotropies of shell sublattices and core ones, respectively. So, one can examine interesting phenomena are compensation behaviors and the free energy of the nanosystem, where these phenomena found that the mixed-spin square Blume-Capel Ising nanosystem which is being considered has two compensation temperatures in the range of −0.8≤DB|J1|≤−0.4, respectively.

The study of half-metallic behavior, thermoelectric properties and thermodynamic stability of the new quaternary PdZrTiAl Heusler were carried out based on the Density Functional Theory (DFT) calculations. The generalized gradient approximation with Tran-Blaha potential (GGA + mbJ) was utilized to treat the exchange-correlation energy for the calculations of electronic structures. More accurate results of the dynamic stability investigation of the intended Heusler compound were obtained by using and Quantum Molecular Dynamic (QMD) simulation. Calculation of the electronic structure indicates that the PdZrTiAl compound has an indirect band gap 0.69eV (from GGA + mbJ) in the down spin and therefore is a ferromagnetic half-metal with 3.00μB magnetic moment. The investigation of the thermodynamic phase diagram showed that this material is stable in all thermodynamic conditions. Furthermore, the phonon positive frequencies and the results of QMD, confirms the sustainability of this structure in XX΄YZ stoichiometric compound. The elastic constants reveal that the PdZrTiAl are mechanically stable and the Poisson's ratio confirmed that the alloys considered are ductile. Also, thermoelectric properties of this compound were studied using transport quasi-classical theory. It was observed that in two majority and minority spin states, this combination shows an utterly distinct thermoelectric behavior. This compound has a good merit coefficient at dn spin at all temperature ranges, especially at low temperatures and the negative sign of the Seebeck coefficient indicates that electrons are charge carriers.

We study theoretically the electronic structure of topological nodal-line semimetals. We show that, in the presence of a gap-opening spatially dependent mass term that forms a domain wall, an in-gap charged localized mode emerges at the domain wall. It turns out that such a domain wall is realized by head-to-head (or tail-to-tail) bulk electric polarizations. The dispersion of the localized mode evolves from gapless to gapped as the bulk bandgap increases, which means that its conductivity is tunable. The localized mode has a topological origin, i.e., a topological confinement is realized, which is understood by a semiclassical topological number defined in semiclassical momentum-real space. In contrast to previous studies, the origin of the charged domain wall in this study is purely electronic, i.e., due to the band topology. Moreover, this study demonstrates a topological confinement at the interface between two insulators without bulk topological numbers. We discuss a possible experimental realization of the stable, electrically-tunable charged domain wall.

We systematically study the indirect interaction between a magnon mode and a cavity photon mode mediated by traveling photons of a waveguide. From a general Hamiltonian, we derive the effective coupling strength between two separated modes, and obtain the theoretical expression of system’s transmission. Accordingly, we design an experimental set-up consisting of a shield cavity photon mode, a microstrip line and a magnon system to test our theoretical predictions. From measured transmission spectra, indirect interaction, as well as mode hybridization, between two modes can be observed. All experimental observations support our theoretical predictions. In this work, we clarify the mechanism of traveling photon mediated interactions between two separate modes. Even without spatial mode overlap, two separated modes can still couple with each other through their correlated dissipations into a mutual traveling photon bus. This conclusion may help us understand the recently discovered dissipative coupling effect in cavity magnonics systems. Additionally, the physics and technique developed in this work may benefit us in designing new hybrid systems based on the waveguide magnonics.

We investigate the effects of lithium intercalation in twisted bilayers of graphene, using first-principles electronic structure calculations. To model this system we employ commensurate supercells that correspond to twist angles of 7.34∘ and 2.45∘. From the energetics of lithium absorption we demonstrate that for low Li concentration the intercalants cluster in the AA regions with double the density of a uniform distribution. The charge donated by the Li atoms to the graphene layers results in modifications to the band structure that can be qualitatively captured using a continuum model with modified interlayer couplings in a region of parameter space that has yet to be explored either experimentally or theoretically. Thus, the combination of intercalation and twisted layers simultaneously provides the means for spatial control over material properties and an additional knob with which to tune physics in twisted bilayers of graphene, with potential applications ranging from energy storage and conversion to quantum information.

Exciting solids with intense femtosecond laser pulses prompts electrons of the interrogated material to respond in highly non-linear manner, as is evident in the emission of high-order harmonic radiation and photoelectrons with kinetic energies well above that of the driving photons. Such high-field interactions can be resolved, for example, in above-threshold multiphoton photoemission (ATP) spectroscopy. In this work, we interrogate the nonlinear photoelectric responses of the pristine copper, silver, and gold noble metal surfaces in (111) and (100) crystal orientations in the perturbative regime. Using multi-photon photoemission spectroscopy (mPP) excited by finely tuned optical fields, we characterize enhancement of the mPP and ATP yields from (111) surfaces in selected k||-momentum ranges when the occupied Shockley surface (SS) states are (near-)resonantly coupled by multi-photon transitions to image potential (IP) intermediate states in the excitation process. The ATP signal from the IP states of (111) surfaces is largely defined by their formation through polarization of SS electrons; this observation is contrasted with ATP experiments from the Ag(100) surface, for which the SS becomes an unoccupied resonance and the IP states can only be excited from bands with significantly more bulk character. In addition, based on the optical power and non-linear order dependent mPP spectra, we provide new evidence for ATP being a one-step, rather than a sequential process, as previously postulated.

Structural symmetry breaking and recovery in condensed matter systems are closely related to exotic physical properties such as superconductivity (SC), magnetism, spin density waves (SDW) and charge density waves (CDW). The interplay between different order parameters is intricate and often subject to intense debate, as in the case of CDW order and superconductivity. In La1.875Ba0.125CuO4 (LBCO), the low-temperature structural domain walls are hypothesized as nanometer scale pinning sites for the CDWs. Coherent X-ray diffraction techniques have been employed here to visualize the domain structures associated with these symmetry changes directly during phase transition. We have pushed Bragg Coherent Diffractive Imaging (BCDI) into the cryogenic regime where most phase transitions in quantum materials reside. Utilizing BCDI, we image the structural evolution of LBCO microcrystal samples during the high-temperature tetragonal (HTT) to low-temperature orthorhombic (LTO) phase transition. Our results show the formation of LTO domains close to the transition temperature and how the domain size decreases with temperature. The number of domains follows the secondary order parameter (or orthorhombic strain) measurement with a critical exponent that is consistent with the 3D universality class.

Nanoscale mechanical resonators are widely utilized to provide high sensitivity force detectors. Here we demonstrate that such high quality factor resonators immersed in superfluid (^4He) can be excited by a modulated flux of phonons. A nanosized heater immersed in superfluid (^4He) acts as a source of ballistic phonons in the liquid – "phonon wind". When the modulation frequency of the phonon flux matches the resonance frequency of the mechanical resonator, the motion of the latter can be excited. This ballistic thermomechanical effect can potentially open up new types of experiments in quantum fluids.

Transport properties of permalloy doped with V, Co, Pt, and Au are explored via ab-initio calculations. the Kubo-Bastin formula is evaluated within the fully relativistic Korringa-Kohn-Rostoker Green function formalism. Finite temperature effects are treated by means of the alloy analogy model. It is shown that the fact that the host is disordered and not crystalline has a profound effect on how the conductivities characterizing the anomalous Hall effect and the spin Hall effect depend on the dopant concentration. Several relationships between quantities characterizing charge and spin transport are highlighted. The decrease of the longitudinal charge conductivity with increasing doping depends on the dopant type, following the sequence Co–Au–Pt–V. The dependence of the anomalous Hall and spin Hall conductivities on the dopant concentration is found to be non-monotonic. Introducing a finite temperature changes the overall trends significantly. The theoretical results are compared with available experimental data.

In the absence of dissipation a periodically driven BCS superconductor can enter a coherent nonlinear regime of collective Rabi oscillations which last for arbitrary long times [Ojeda Collado et al. Phys. Rev. B 98, 214519 (2018)]. Here we show that dissipation effects introduce dramatic changes: i) the collective Rabi mode becomes a transient. ii) At long times a steady state is reached showing strong nonlinear effects for large enough drive strength. We identify the physical parameters governing the various crossovers and present a detailed computation of time- and angle-resolved photo-emission spectroscopy (tr-ARPES) and time-resolved tunneling spectra aiming at detecting the collective Rabi oscillations and the steady-state nonlinearities. We show also that second harmonic generation is allowed for a drive which acts on the BCS coupling constant.

We propose a theoretical scheme exploiting magnetic proximity effect to realize strong excitonic emission and large, nonvolatile valley polarization in monolayer MoS2 at room temperature. A moderate exchange field can lead to valley selective switching of the exciton ground state from bright to dark and a large valley exciton splitting at the same time. The duo work synergistically to achieve a temperature enhanced valley polarization: while a large valley splitting is the critical first step for creating a valley exciton population imbalance, this imbalance is greatly enhanced by thermal excitation from the dark ground state, with orders of magnitude longer lifetime than that of the bright exciton. Realizing robust room temperature emission and valley polarization is essential for controlling the valley degree of freedom for information processing.

We consider the relaxation dynamics of two spins coupled to a common bosonic bath. The time evolution is simulated by a generalized master equation derived within a real-time diagrammatic approach. Interference effects due to the coherent coupling to the common bath give rise to characteristic features in the relaxation dynamics after a quench or during a periodic external driving. In particular, we find that the long-time behavior during periodic driving depends sensitively on the initial state as well as on system parameters such as coupling asymmetries. When coupled to more than a single reservoir, the interference effects can lead to a cooling mechanism for one of the bosonic reservoirs.

The stability of two-dimensional chiral skyrmions in a tilted magnetic field is studied. It is shown that by changing the direction and magnitude of the field, one can continuously transform a chiral skyrmion into a skyrmion with opposite polarity and vorticity. This turned inside out skyrmion can be considered as an antiparticle for ordinary axisymmetric skyrmion. For any tilt angle of the magnetic field, there is a range of its absolute values where two types of skyrmions may coexist. In a tilted field the potentials for inter-skyrmion interactions are characterized by the presence of local minima suggesting attractive interaction between the particles. The potentials of inter-particle interactions also have so-called fusion channels allowing either annihilation of two particles or the emergence of a new particle. The presented results are general for a wide class of magnetic crystals with both easy-plane and easy-axis anisotropy.

We investigate the proximity-induced exchange coupling in transition-metal dichalcogenides (TMDCs), originating from spin injector geometries composed of hexagonal boron-nitride (hBN) and ferromagnetic (FM) cobalt (Co) or nickel (Ni), from first-principles. We employ a minimal tight-binding Hamiltonian that captures the low energy bands of the TMDCs around K and K’ valleys, to extract orbital, spin-orbit, and exchange parameters. The TMDC/hBN/FM heterostructure calculations show that due to the hBN buffer layer, the band structure of the TMDC is preserved, with an additional proximity-induced exchange splitting in the bands. We extract proximity exchange parameters in the 1–10 meV range, depending on the FM. The combination of proximity-induced exchange and intrinsic spin-orbit coupling (SOC) of the TMDCs, leads to a valley polarization, translating into magnetic exchange fields of tens of Tesla. The extracted parameters are useful for subsequent exciton calculations of TMDCs in the presence of a hBN/FM spin injector. Our calculated absorption spectra show large splittings for the exciton peaks; in the case of MoS2/hBN/Co we find a value of about 8 meV, corresponding to about 50 Tesla external magnetic field in bare TMDCs. The reason lies in the band structure, where a hybridization with Co d orbitals causes a giant valence band exchange splitting of more than 10~meV. Structures with Ni do not show any d level hybridization features, but still sizeable proximity exchange and exciton peak splittings of around 2~meV are present in the TMDCs.

We discuss the interplay between magnetic and structural degrees of freedom in elemental Mn. The equilibrium volume is shown to be sensitive to magnetic interactions between the Mn atoms. While the standard generalized-gradient-approximation underestimates the equilibrium volume, a more accurate treatment of the effects of electronic localization and magnetism is found to solve this longstanding problem. Our calculations also reveal the presence of a magnetic phase in strained α-Mn that has been reported previously in experiments. This new phase of strained α-Mn exhibits a noncollinear spin structure with large magnetic moments.

A new compound, NaMnSbO_4, represents a square net of magnetic Mn^2+ ions residing in vertex-shared oxygen octahedra. Its static and dynamic magnetic properties were studied using magnetic susceptibility, specific heat, magnetization, electron spin resonance (ESR), nuclear magnetic resonance (NMR) and density functional calculations. Thermodynamic data indicate an establishment of the long-range magnetic order with T_N ~ 44 K, which is preceded by a short-range one at about 55 K. In addition, a non-trivial wasp-waisted hysteresis loop of the magnetization was observed, indicating that the ground state is most probably canted antiferromagnetic. Temperature dependence of the magnetic susceptibility is described reasonably well in the framework of 2D square lattice model with the main exchange parameter J = -5.3 K, which is in good agreement with density functional analysis, NMR and ESR data.

We report the observation of a two-dimensional electron system (2DES) at the (110) surface of the transparent bulk insulator SnO2, and the tunability of its carrier density by means of temperature or Eu deposition. The 2DES is insensitive to surface reconstructions and, surprisingly, it survives even after exposure to ambient conditions –an extraordinary fact recalling the well known catalytic properties SnO2. Our data show that surface oxygen vacancies are at the origin of such 2DES, providing key information about the long-debated origin of n-type conductivity in SnO2, at the basis of a wide range of applications. Furthermore, our study shows that the emergence of a 2DES in a given oxide depends on a delicate interplay between its crystal structure and the orbital character of its conduction band.

We propose a platform for robust and tunable non-reciprocal phonon transport based on arrays of optomechanical microtoroids. In our approach, time-reversal symmetry is broken by the interplay of photonic spin–orbit coupling, engineered using a state-of-the-art geometrical approach, and the optomechanical interaction. We demonstrate the topologically protected nature of this system by investigating its robustness to imperfections. This type of system could find application in phonon-based information storage and signal processing devices.

The transition between the N'{e}el antiferromagnet and the valence-bond solid state in two dimensions has become a paradigmatic example of deconfined quantum criticality, a non-Landau transition characterized by fractionalized excitations (spinons). We consider an extension of this scenario whereby the deconfined spinons are subject to a magnetic field. The primary purpose is to identify the exotic scenario of a Bose-Einstein condensate of spinons. We employ quantum Monte Carlo simulations of the model with a magnetic field and perform a quantum field theoretic analysis of the magnetic field and temperature dependence of thermodynamic quantities. The combined analysis provides evidence for Bose-Einstein condensation of spinons and also demonstrates an extended temperature regime in which the system is best described as gas of spinons interacting with an emergent gauge field.

In the theory of Anderson localization, a landscape function predicts where wave functions localize in a disordered medium, without requiring the solution of an eigenvalue problem. It is known how to construct the localization landscape for the scalar wave equation in a random potential, or equivalently for the Schr"{o}dinger equation of spinless electrons. Here we generalize the concept to the Dirac equation, which includes the effects of spin-orbit coupling and allows to study quantum localization in graphene or in topological insulators and superconductors. The landscape function u(𝐫) is defined on a lattice as a solution of the differential equation $\overbrack{{H}}u(\bm{r})=1$, where $\overbrack{{H}}$ is the Ostrowsky comparison matrix of the Dirac Hamiltonian. Random Hamiltonians with the same (positive definite) comparison matrix have localized states at the same positions, defining an equivalence class for Anderson localization. This provides for a mapping between the Hermitian and non-Hermitian Anderson model.

The electron-nuclei hyperfine interaction of electrons in indirect band gap (In,Al)As/AlAs quantum dots with type-I band alignment has been experimentally studied by measuring the polarization degree of the photoluminescence in a transverse magnetic field (Hanle effect) and the polarization recovery in a longitudinal magnetic field. The different symmetry of the X valley electron Bloch amplitudes at the As, In, and Al nuclei strongly affects the hyperfine interaction. The hyperfine constants corresponding to these nuclei have been determined.

The current I through nickelocene molecules and its noise are measured with a low temperature scanning tunneling microscope on a Cu(100) substrate. Density functional theory calculations and many-body modeling are used to analyze the data. During contact formation, two types of current evolution are observed, an abrupt jump to contact and a smooth transition. These data along with conductance spectra (dI/dV) recorded deep in the contact range are interpreted in terms of a transition from a spin-1 to a spin- state that is Kondo screened. Many-body calculations show that the smooth transition is also consistent with a renormalization of spin excitations of a spin-1 molecule by Kondo exchange coupling. The shot noise is significantly reduced compared to the Schottky value of 2eI. The noise can be described in the Landauer picture in terms of the spin polarization of the transmission of ≈35,% through two degenerate dπ-orbitals of the Nickelocene molecule.

We present a new method to treat the two-dimensional (2D) Hubbard model for parameter regimes which are relevant for the physics of the high-Tc superconducting cuprates. Unlike previous attempts to attack this problem, our new approach takes into account all fluctuations in different channels on equal footing and is able to treat reasonable large lattice sizes up to 32x32. This is achieved by the following three-step procedure: (i) We transform the original problem to a new representation (dual fermions) in which all purely local correlation effects from the dynamical mean field theory are already considered in the bare propagator and bare interaction of the new problem. (ii) The strong 1/(iν)2 decay of the bare propagator allows us to integrate out all higher Matsubara frequencies besides the lowest using low order diagrams. The new effective action depends only on the two lowest Matsubara frequencies which allows us to, (iii) apply the two-particle self-consistent parquet formalism, which takes into account the competition between different low-energy bosonic modes in an unbiased way, on much finer momentum grids than usual. In this way, we were able to map out the phase diagram of the 2D Hubbard model as a function of temperature and doping. Consistently with the experimental evidence for hole-doped cuprates and previous dynamical cluster approximation calculations, we find an antiferromagnetic region at low-doping and a superconducting dome at higher doping. Our results also support the role of the van Hove singularity as an important ingredient for the high value of Tc at optimal doping. At small doping, the destruction of antiferromagnetism is accompanied by an increase of charge fluctuations supporting the scenario of a phase separated state driven by quantum critical fluctuations.

We report comprehensive temperature and doping-dependences of the Raman scattering spectra for (x= 0, 0.07, 0.24, 0.32, and 0.38), focusing on the nematic fluctuation and the superconducting responses. With increasing x, the bare nematic transition temperature estimated from the Raman spectra reaches T= 0 K at the optimal doping, which indicates a quantum critical point (QCP) at this composition. In the superconducting compositions, in addition to the pair breaking peaks observed in the and spectra, another strong peak appears below the superconducting transition temperature which is ascribed to the nematic resonance peak. The observation of this peak indicates significant nematic correlations in the superconducting state near the QCP in this compound.

Fractons emerge as charges with reduced mobility in a new class of gauge theories. Here, we generalise fractonic theories of U(1) type to what we call (k,n)-fractonic Maxwell theory, which employs symmetric rank-n tensors of k-forms (rank-k antisymmetric tensors) as vector potentials''. The generalisation, valid in any spatial dimension $d$, has two key manifestations. First, the objects with mobility restrictions extend beyond simple charges to higher order multipoles (dipoles, quadrupoles, $\ldots$) all the way to $n^th$-order multipoles, which we call the order-$n$ fracton condition. Second, these fractonic charges themselves are characterized by tensorial densities of $(k-1)$-dimensional extended objects. For any $(k,n)$, the theory can be constructed to have a gaplessphoton modes’’ with dispersion ω∼|q|z, where the integer z can range from 1 to n.

We develop a method for finding the time evolution of exactly solvable models by Bethe ansatz, with Hilbert space linear in excitation number. The dynamical Bethe wavefunction takes the same form as the stationary Bethe wavefunction except for time varying Bethe parameters and a complex phase prefactor. From this, we derive a set of first order nonlinear coupled differential equations for the Bethe parameters, called the dynamical Bethe equations. We find that this gives the exact solution to particular types of exactly solvable models, including the Bose-Hubbard dimer. The developed formalism allows us to demonstrate analytically that time dynamics of the detuning-quenched Bose-Hubbard dimer occurs in the subspace which dimensionality is less than that of physical Hilbert space. This allows for calculating the time dynamics within a reduced problem dimensionality.

We report microwave power driven strong magnon-magnon coupling in Ni80Fe20 nano-cross array with large anticrossing gaps up to 1.03 GHz. We also observe microwave driven large nonlinear shift in ferromagnetic resonance frequency (FMR) with its sign dependent on the strength of bias magnetic field. A drastic enhancement of inter nano-cross dynamic dipolar interaction results in the anticrossing, while variation in internal spin texture leads to the nonlinear FMR shift. The tunable coupling strength and nonlinearity by microwave power ushers externally controlled nonlinear magnonic devices.

We report numerical simulations of large-amplitude oscillations of a trapped vortex line under a strong ac magnetic field H(t)=Hsinωt parallel to the surface. The power dissipated by an oscillating vortex segment driven by the surface ac Meissner currents was calculated by taking into account the nonlinear vortex line tension, vortex mass and a nonlinear Larkin-Ovchinnikov (LO) viscous drag coefficient η(v). We show that the LO decrease of η(v) with the vortex velocity v can radically change the field dependence of the surface resistance Ri(H) caused by trapped vortices. At low frequencies $R_i(H) $ exhibits a conventional increases with H, but as ω increases, the surface resistance becomes a nonmonotonic function of H which {} with H at higher fields. The effects of frequency, pin spacing and the mean free path $l_i $ on the field dependence of $R_{i}(H) $ were calculated. It is shown that, as the surface gets dirtier and li decreases, the anomalous drop of $ R_{i}(H) $ with H shifts to lower fields which can be much smaller than the lower critical magnetic field. Our numerical simulations also show that the LO decrease of η(v) with v can cause a vortex bending instability at high field amplitudes and frequencies, giving rise to the formation of dynamic kinks along the vortex. Measurements of Ri(H) caused by sparse vortices trapped perpendicular to the surface can offer opportunities to investigate an extreme nonlinear dynamics of vortices driven by strong current densities up to the depairing limit at low temperatures. The behavior of Ri(H) which can be tuned by varying the rf frequency or concentration of nonmagnetic impurities is not masked by strong heating effects characteristic of dc or pulse transport measurements.

The isotropic, non-magnetic doped BaBiO3 superconductors maintain some similarities to high-Tc cuprates, while also providing a cleaner system for isolating charge density wave (CDW) physics that commonly competes with superconductivity. Artificial layered superlattices offer the possibility of engineering the interaction between superconductivity and CDW. Here we stabilize a low temperature, fluctuating short range CDW order by using artificially layered epitaxial (BaPbO3)3m/(BaBiO3)m (m = 1-10 unit cells) superlattices that is not present in the optimally doped BaPb0.75Bi0.25O3 alloy with the same overall chemical formula. Charge transfer from BaBiO3 to BaPbO3 effectively dopes the former and suppresses the long range CDW, however as the short range CDW fluctuations strengthens at low temperatures charge appears to localize and superconductivity is weakened. The monolayer structural control demonstrated here provides compelling implications to access controllable, local density-wave orders absent in bulk alloys and manipulate phase competition in unconventional superconductors.

We report characteristic vortex configurations in s+id superconductors with time reversal symmetry breaking, exposed to magnetic field. A vortex in the s+id state tends to have an opposite phase winding between s− and d−wave condensates. We find that this peculiar feature together with the competition between s− and d−wave symmetry results in three distinct classes of vortical configurations. When either s− or d− condensate absolutely dominates, vortices form a conventional lattice. However, when one condensate is relatively dominant, vortices organize in chains that exhibit skyrmionic character, separating the chiral components of the s±id order parameter into domains within and outside the chain. Such skyrmionic chains are found stable even at high magnetic field. When s− and d− condensates have a comparable strength, vortices split cores in two chiral components to form full-fledged skyrmions, i.e. coreless topological structures with an integer topological charge, organized in a lattice. We provide characteristic magnetic field distributions of all states, enabling their identification in e.g. scanning Hall probe and scanning SQUID experiments. These unique vortex states are relevant for high-Tc cuprate and iron-based superconductors, where the relative strength of competing pairing symmetries is expected to be tuned by temperature and/or doping level, and can help distinguish s+is and s+id superconducting phases.