Intrinsic Coupling Research Articles

Optimal Operation of Energy Hubs With Large-Scale Distributed Energy Resources for Distribution Network Congestion Management

Congestion problems might occur in distribution networks as the penetration of distributed energy resources (DERs) progresses. This study focuses on the complementarity of multiple energy resources in energy hubs (EHs) to solve possible distribution network congestions. First, we consider an EH in which combined cooling, heating and power (CCHP) units and heat pumps are integrated with renewable energy resources. The EH models the intrinsic coupling relationship among various energy carriers, forming a flexible operation where electricity, natural gas, cooling and heat can complement each other. Next, an optimal operation strategy of multiple energy hubs enables gas-to-electricity to provide local energy supply for EH during electricity peak periods, and consume renewable energy generation by the complementarity of electricity, heat and cooling. In addition, the uncertainty of renewable energy resources is taken into account via scenario-based stochastic programming. Numerical results show that the proposed operation strategy explores EHs’ operation flexibility to mitigate distribution network congestion when we consider high renewable energy penetration in power systems.

Intrinsic and extrinsic spin-orbit coupling and spin relaxation in monolayer PtSe2

Monolayer PtSe$_2$ is a semiconducting transition metal dichalcogenide characterized by an indirect band gap, space inversion symmetry, and high carrier mobility. Strong intrinsic spin-orbit coupling and the possibility to induce extrinsic spin-orbit fields by gating make PtSe$_2$ attractive for fundamental spin transport studies as well as for potential spintronics applications. We perform a systematic theoretical study of the spin-orbit coupling and spin relaxation in this material. Specifically, we employ first principles methods to obtain the basic orbital and spin-orbital properties of PtSe$_2$, also in the presence of an external transverse electric field. We calculate the spin mixing parameters $b^2$ and the spin-orbit fields $\Omega$ for the Bloch states of electrons and holes. This information allows us to predict the spin lifetimes due to the Elliott-Yafet and D'yakonov-Perel mechanisms. We find that $b^2$ is rather large, on the order of $10^{-2}$ and $10^{-1}$, while $\Omega$ varies strongly with doping, being about $10^{3} - 10^{4}$\,ns$^{-1}$ for %typical Fermi levels in the interval $(10-100)$ meV, carrier density in the interval $10^{13}-10^{14}$\,cm$^{-2}$ at the electric field of 1 V/nm. We estimate the spin lifetimes to be on the picosecond level.

Interaction-induced topological superconductivity in antiferromagnet-superconductor junctions

We predict that junctions between an antiferromagnetic insulator and a superconductor provide a robust platform to create a one-dimensional topological superconducting state. Its emergence does not require the presence of intrinsic spin-orbit coupling nor non-collinear magnetism, but arises solely from repulsive electronic interactions on interfacial solitonic states. We demonstrate that a topological superconducting state is generated by repulsive interactions at arbitrarily small coupling strength, and that the size of the topological gap rapidly saturates to the one of the parent trivial superconductor. Our results put forward antiferromagnetic insulators as a new platform for interaction-driven topological superconductivity.

Room temperature multiferroic properties of BiFeO3–MnFe2O4 nanocomposites

The novel functionalities of multiferroic magneto-electric nanocomposites have spawned substantial scope for fast-paced memory devices and sensor applications. Following this, herein we report the development of nanocomposites with soft ferromagnetic MnFe2O4 and ferroelectric BiFeO3 to fabricate a system with engineered multiferroic properties. A modified sol-gel route called Pechini method is demonstrated for the preparation of the (1-x) BiFeO3-x MnFe2O4 (x = 10%, 30%, 50%, 70%) nanocomposites. The crystallographic phase, structure, and morphology are characterized by XRD, FESEM, and HRTEM. The accurate crystallite size and lattice strain are determined by Williamson-Hall plot method and a comparative study with Scherer's equation is carried out. TEM image evidences the interface between BiFeO3 and MnFe2O4 nanoparticles in the composite. The room temperature magnetic response reveals the strong dependence of magnetic saturation, remanent magnetization, and coercivity of the nanocomposites on MnFe2O4 addition. The dielectric response and impedance analysis of the prepared nanocomposites are observed. The electrical performance of the composite is affected by grain, grain boundaries, and oxygen vacancies. The unsaturated P-E loops exhibit the leaky ferroelectric behavior for the nanocomposite. The intrinsic magnetoelectric coupling between ferroelectric BiFeO3 and ferromagnetic MnFe2O4 has been determined by varying Hdc/Hac and its maximum coupling coefficient (α) is found to be 25.39 mV/cmOe for 70% BiFeO3 -30% MnFe2O4 nanocomposite. These distinctive and achievable characteristics of the nanocomposite would enable the designing of magnetic field sensors, spintronic devices, and multiferroic memory devices.

Intrinsic polarization coupling in 2D α‐In2Se3toward artificial synapse with multimode operations

AbstractEmulation of advanced synaptic functions of the human brain with electronic devices contributes an important step toward constructing high‐efficiency neuromorphic systems. Ferroelectric materials are promising candidates as synaptic weight elements in neural network hardware due to their controllable polarization states. However, the increased depolarization field at the nanoscale and the complex fabrication process of the traditional ferroelectric materials hamper the development of high‐density, low‐power, and highly sensitive synaptic devices. Here, we report the implementation of two‐dimensional (2D) ferroelectric α‐In2Se3as an active channel material to emulate typical synaptic functions. The α‐In2Se3‐based synaptic device features multimode operations, enabled by the coupled ferroelectric polarization under various voltage pulses applied at both drain and gate terminals. Moreover, the energy consumption can be reduced to ~ 1 pJ by using high‐κdielectric (Al2O3). The successful control of ferroelectric polarizations in α‐In2Se3and its application in artificial synapses are expected to inspire the implementation of 2D ferroelectric materials for future neuromorphic systems.

Two-dimensional centrosymmetrical antiferromagnets for spin photogalvanic devices

Spin-dependent photogalvanic effect (PGE) in low-dimensional magnetic systems has recently attracted intensive attention. Based on first-principle transport calculations and symmetry analyses, we propose a robust scheme to generate pure spin current by PGE in centrosymmetric materials with spin polarization antisymmetry. As a demonstration, the idea is successfully applied to a photoelectric device constructed with a zigzag graphene nanoribbon (ZGNR), which has intrinsic antiferromagnetic coupling between the two edges and spin degenerate band structure. It suggests that spin splitting is not a prerequisite for pure spin current generation. More interestingly, by further introducing external transverse electric fields to the two leads to lift the spin degeneracy, the device may behave multifunctionally, capable of producing fully spin-polarized current or pure spin current, depending on whether the fields in the two leads are parallel or antiparallel. Very importantly, our scheme of pure spin current generation with PGE is not limited to ZGNR and can be extended to other two-dimensional (2D) centrosymmetric magnetic materials with spin polarization antisymmetry, suggesting a promising category of 2D platforms for PGE-based pure spin current generation.

Permittivity order modulation by intrinsic dielectric coupling

The room-temperature permittivity is reduced by one order of magnitude in a wide frequency range during each step, when the stoichiometric proportion of Cu in CaCu3Ti4O12 is decreased from 3 to 2 and then to 1. The frequency-independent reduction can be applied down to 140 K. Such an almost frequency- and temperature-independent decrease in the permittivity magnitude order suggests the existence of intrinsic dielectric coupling between binary dielectric polarization species, by which the less polaron-like 3d electrons from B-site copper ions more strongly depress the permittivity contribution from one-dimensional, anti-parallel, mutually independent, and finite length dipole chains of thermally activated off-center displacements of A-site titanium ions.

Structural and magnetodielectric properties of BiFeO3-GdMnO3 multiferroics

We report on structural, microstructural, spectroscopic, dielectric, electrical, ferroelectric, ferromagnetic, and magnetodielectric coupling studies of BiFeO3–GdMnO3[(BFO)1–x –(GMO) x ], where x is the concentration of GdMnO3 (x = 0.0, 0.025, 0.05, 0.075, 0.1, 0.15, and 0.2), nanocrystalline ceramic solid solutions by auto-combustion method. The analysis of structural property by Rietveld refinement shows the existence of morphotropic phase boundary (MPB) at x = 0.10, which is in agreement with the Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) studies. The average crystallite size obtained from the transmission electron microscopy (TEM) and x-ray line profile analysis was found to be 20–30 nm. The scanning electron micrographs show the uniform distribution of grains throughout the surface of the sample. The dielectric dispersion behavior fits very well with the Maxwell-Wagner model. The frequency dependent phase angle (θ) study shows the resistive nature of solid solutions at low frequency, whereas it shows capacitive behavior at higher frequencies. The temperature variation of dielectric permittivity shows dielectric anomaly at the magnetic phase transition temperature and shifting of the phase transition towards the lower temperature with increasing GMO concentration. The Nyquist plot showed the conduction mechanism is mostly dominated by grains and grain boundary resistances. The ac conductivity of all the samples follows the modified Jonscher model. The impedance and modulus spectroscopy show a non-Debye type relaxation mechanism which can be modeled using a constant phase element (CPE) in the equivalent circuit. The solid-solutions of BFO-GMO show enhanced ferromagnetic-like behavior at room temperature. The ferroelectric polarization measurement shows lossy ferroelectric behavior. The frequency dependent magnetocapacitance and magnetoimpedance clearly show the existence of intrinsic magnetodielectric coupling. The (BFO)1–x –(GMO) x solid solutions with x = 0.025–0.075 show significantly higher magnetocapacitance and magnetoimpedance compared to the pure BFO.

Impact of high-speed railway construction on spatial relationships in the Guanzhong Plain urban agglomeration

The Guanzhong Plain urban agglomeration is a response to the Belt and Road Initiative in Northwest China that aims to promote regional development. The direct impact of high-speed railway construction is to shorten the spatial-temporal distance among regions, improve the accessibility of regional transportation, and promote socioeconomic linkages. From the perspective of accessibility, this study analyzes the impact of high-speed railway construction on the spatial patterns and county-level economic relationships of the Guanzhong Plain urban agglomeration. The results show that the construction of high-speed railway significantly improves regional accessibility, increases the potential for urban economic development, and gradually narrows the gaps in economic potential among cities. The construction of high-speed railway has increased the intensity of external economic relations among numerous counties in the Guanzhong Plain urban agglomeration, and most of the areas with increased connections are located in the direction of routes extension. The development of the internal economic network of the Guanzhong Plain urban agglomeration is unbalanced, and a complex network is gradually emerging with a few large cities at the core, but the construction of high-speed railway is changing the structure of the economic network. In general, a certain degree of intrinsic coupling exists between regional accessibility change and the evolution of economic relations caused by high-speed railway, reflecting the requirements of the regional overall development strategy.

Sublattice symmetry breaking and ultralow energy excitations in graphene-on- hBN heterostructures

The low-lying states of graphene contain exciting topological properties that depend on the interplay of different symmetry breaking terms. The corresponding energy gaps remained unexplored until recently, owing to the low energy scale of the terms involved (few tens of ueV). These low energy terms include sublattice splitting, the Rashba and the intrinsic spin-orbit coupling, whose balance determines the topological properties. In this work, we unravel the contributions arising from the sublattice and the intrinsic spin orbit splitting in graphene on hexagonal boron-nitride. Employing resistively-detected electron spin resonance, we measure a sublattice splitting of the order of 20E-6 eV, and confirm an intrinsic spin orbit coupling of approximately 45E-6 eV. The dominance of the latter suggests a topologically non-trivial state, involving fascinating properties. Electron spin resonance is a promising route towards unveiling the intriguing band structure at low energy scales.

The default network of the human brain is associated with perceived social isolation

Humans survive and thrive through social exchange. Yet, social dependency also comes at a cost. Perceived social isolation, or loneliness, affects physical and mental health, cognitive performance, overall life expectancy, and increases vulnerability to Alzheimer’s disease-related dementias. Despite severe consequences on behavior and health, the neural basis of loneliness remains elusive. Using the UK Biobank population imaging-genetics cohort (n = ~40,000, aged 40–69 years when recruited, mean age = 54.9), we test for signatures of loneliness in grey matter morphology, intrinsic functional coupling, and fiber tract microstructure. The loneliness-linked neurobiological profiles converge on a collection of brain regions known as the ‘default network’. This higher associative network shows more consistent loneliness associations in grey matter volume than other cortical brain networks. Lonely individuals display stronger functional communication in the default network, and greater microstructural integrity of its fornix pathway. The findings fit with the possibility that the up-regulation of these neural circuits supports mentalizing, reminiscence and imagination to fill the social void.

107 Skeletal muscle mitochondrial parameters correlate with sales price in weanling racing-bred Thoroughbred horses

Abstract Thoroughbred horse sales prices rely heavily on animal conformation and ancestral race performance, as well as the current economic landscape. However, little information exists on the relationship between physiological parameters and sales price. We aimed to test the hypothesis that weanling sales price would positively correlate with skeletal muscle mitochondrial parameters in racing-bred Thoroughbreds. Gluteus medius muscle samples were collected from racing-bred Thoroughbred weanlings (n = 19; mean ± SD; 5.7 ± 0.3 mo) and evaluated for mitochondrial volume density (citrate synthase activity; CS) and function (cytochrome c oxidase activity; COX) by colorimetry, and oxidative and electron transport system capacities by high resolution respirometry. Horses were sold at the 2018 and 2019 Keeneland November Breeding Stock Sales at 8.5 ± 0.7 mo of age. Data were analyzed using Pearson Correlation Statistics in SAS (v9.4). Weanling sales price was positively correlated with intrinsic mitochondrial function (COX activity per unit CS; r = 0.6269, P = 0.004) and coupling efficiency with substrates for complex I+II (r = 0.4424, P = 0.05). A trend for a negative correlation was observed between weanling sales price and CS activity (r = -0.4179, P = 0.07), while a trend for a positive correlation between sales price and intrinsic oxidative phosphorylation capacity with complex I substrates (r = 0.3974, P = 0.09) was observed. In this cohort of weanling Thoroughbreds, mitochondrial parameters measured at 6 mo of age correlated with sales price at 8 mo of age. Implications of these relationships as they relate to race performance should be further investigated.

Dislocation-induced large local polarization inhomogeneity of ferroelectric materials

Dislocations in ferroelectrics play important roles in ferroelectricity, piezoelectricity, and dielectricity. However, the intrinsic charge-lattice coupling mechanism in ferroelectric crystals containing dislocations is still not well understood. Here, we report a large local polarization inhomogeneity of ~100 μCcm−2 induced by a single a[001] dislocation in the PbZr0.2Ti0.8O3/SrTiO3 film/substrate heterostructure, the tensile region (~120 μCcm−2) and the compressive strain region (~21 μCcm−2) around the dislocation forms a butterfly-like area. This study reveals the dramatic effects of dislocations on local polarization and provides a strategy to manipulate the polarization magnitude and orientation of local polarization by defect engineering.

A Nano-Micro Engineering Nanofiber for Electromagnetic Absorber, Green Shielding and Sensor

HighlightsThe role of electron transport characteristics in electromagnetic (EM) attenuation can be generalized to other EM functional materials.The integrated functions of efficient EM absorption and green shielding open the view of EM multifunctional materials.A novel sensing mechanism based on intrinsic EM attenuation performance and EM resonance coupling effect is revealed.It is extremely unattainable for a material to simultaneously obtain efficient electromagnetic (EM) absorption and green shielding performance, which has not been reported due to the competition between conduction loss and reflection. Herein, by tailoring the internal structure through nano-micro engineering, a NiCo2O4 nanofiber with integrated EM absorbing and green shielding as well as strain sensing functions is obtained. With the improvement of charge transport capability of the nanofiber, the performance can be converted from EM absorption to shielding, or even coexist. Particularly, as the conductivity rising, the reflection loss declines from − 52.72 to − 10.5 dB, while the EM interference shielding effectiveness increases to 13.4 dB, suggesting the coexistence of the two EM functions. Furthermore, based on the high EM absorption, a strain sensor is designed through the resonance coupling of the patterned NiCo2O4 structure. These strategies for tuning EM performance and constructing devices can be extended to other EM functional materials to promote the development of electromagnetic driven devices.Graphic

Ferroelectricity-induced multiorbital odd-frequency superconductivity in SrTiO3

We demonstrate that SrTiO$_3$ can be a platform for observing the bulk odd-frequency superconducting state owing to the multiorbital/multiband nature. We consider a three-orbital tight-binding model for SrTiO$_3$ in the vicinity of a ferroelectric critical point. Assuming an intraorbital spin-singlet $s$-wave superconducting order parameter, it is shown that the odd-frequency pair correlations are generated due to the intrinsic LS coupling which leads to the local orbital mixing. Furthermore, we show the existence of additional odd-frequency pair correlations in the ferroelectric phase, which is induced by an odd-parity orbital hybridization term proportional to the ferroelectric order parameter. We also perform a group theoretical classification of the odd-frequency pair amplitudes based on the fermionic and space group symmetries of the system. The classification table enables us to predict dominant components of the odd-frequency pair correlations based on the symmetry of the normal state Hamiltonian that we take into account. Furthermore, we show that experimental signatures of the odd-parity orbital hybridization, which is an essential ingredient for the ferroelectricity-induced odd-frequency pair correlations, can be observed in the spectral functions and density of states.

Universal conductance dips and fractional excitations in a two-subband quantum wire

We theoretically investigate a quasi-one-dimensional quantum wire, where the lowest two subbands are populated, in the presence of a helical magnetic field. We uncover a backscattering mechanism involving the helical magnetic field and Coulomb interaction between the electrons. The combination of these ingredients results in scattering resonances and partial gaps which give rise to non-standard plateaus and conductance dips at certain electron densities. The positions and values of these dips are independent of material parameters, serving as direct transport signatures of this mechanism. Our theory applies to generic quasi-one-dimensional systems, including a Kondo lattice and a quantum wire subject to intrinsic or extrinsic spin-orbit coupling. Observation of the universal conductance dips would identify a strongly correlated fermion system hosting fractional excitations, resembling the fractional quantum Hall states.

A collection of programs for one-dimensional Ising analysis of linear repeat proteins with point substitutions.

A collection of programs is presented to analyze the thermodynamics of folding of linear repeat proteins using a 1D Ising model to determine intrinsic folding and interfacial coupling free energies. Expressions for folding transitions are generated for a series of constructs with different repeat numbers and are globally fitted to transitions for these constructs. These programs are designed to analyze Ising parameters for capped homopolymeric consensus repeat constructs as well as heteropolymeric constructs that contain point substitutions, providing a rigorous framework for analysis of the effects of mutation on intrinsic and directional (i.e., N- vs. C-terminal) interfacial coupling free-energies. A bootstrap analysis is provided to estimate parameter uncertainty as well as correlations among fitted parameters. Rigorous statistical analysis is essential for interpreting fits using the complex models required for Ising analysis of repeat proteins, especially heteropolymeric repeat proteins. Programs described here are available at https://github.com/barricklab-at-jhu/Ising_programs.

Band-Gap Sensitived Seebeck Effect in Heavy Group-IV Monolayers

We have systematically investigated the spin- and valley-dependent Seebeck effect in irradiated heavy group-IV monolayers including silicene, germanene, and stanene by means of semi-classical Boltzmann equation in diffusive regime. Due to the interplay of strong intrinsic spin-orbit coupling, perpendicular electric field, and off-resonant light field, the temperature-driven spin and valley conductivity can be controllable effectively. Except for numerical results, the amplitude of Seebeck coefficient is analyzed and found to be in direct proportion to the band gap at high temperature. It supplies a flexible method to modulate the Seebeck effect. In addition, we have compared the thermoelectric transport properties of different group-IV materials and found that the figure of merit shows great enhancement from silicene to stanene. These findings are excepted to provide a platform for the heavy group-IV materials in future spin–valley thermal and energy-saving devices.

Landau levels in spin-orbit coupling proximitized graphene: Bulk states

We study the magnetic-field dependence of Landau levels in graphene proximitized by large spin-orbit coupling materials, such as transition-metal dichalcogenides or topological insulators. In addition to the Rashba coupling, two types of intrinsic spin-orbit interactions, uniform (Kane-Mele type) and staggered (valley Zeeman type), are included, to resolve their interplay with magnetic orbital effects. Employing a continuum model approach, we derive analytic expressions for low-energy Landau levels, which can be used to extract local orbital and spin-orbit coupling parameters from scanning probe spectroscopy experiments. We compare different parameter regimes to identify fingerprints of relative and absolute magnitudes of intrinsic spin-orbit coupling in the spectra. The inverted band structure of graphene proximitized by WSe$_2$ leads to an interesting crossing of Landau states across the bulk gap at a crossover field, providing insights into the size of Rashba spin-orbit coupling. Landau level spectroscopy can help to resolve the type and signs of the intrinsic spin-orbit coupling by analyzing the symmetry in energy and number of crossings in the Landau fan chart. Finally, our results suggest that the strong response to the magnetic field of Dirac electrons in proximitized graphene can be associated with extremely large self-rotating magnetic moments.

Giant enhancement of the in-plane critical field for thin Al films via proximity coupling to a topological insulator

A topological superconducting state can be induced in the surface state of a topological insulator (TI) by way of proximity coupling to a conventional $s$-wave superconductor ($s\ensuremath{-}\mathrm{SC}$). Planar $s\ensuremath{-}\mathrm{SC}/\mathrm{TI}$ junction structures were proposed as a scalable platform for controlled generation and manipulation of Majorana zero mode (MZM), which holds intriguing promise for fault-tolerant quantum computing. Despite intensive research efforts, the presence of MZM has not been definitively demonstrated in $s\ensuremath{-}\mathrm{SC}/\mathrm{TI}/s\ensuremath{-}\mathrm{SC}$ lateral junctions. A key factor is a lack of direct measurement and quantitative understanding of the proximity coupling between the $s\ensuremath{-}\mathrm{SC}$ and TI. Here we report evidence for strong superconducting proximity effect between a three-dimensional strong TI and Al, a conventional $s\ensuremath{-}\mathrm{SC}$ with minimal intrinsic spin-orbit coupling, in the form of pronounced enhancement of the in-plane critical field (${H}_{c||}$) of the thin Al. Specifically, the ${H}_{c||}$ of a 6-nm-thick Al film deposited on a TI is found to be 2.7 times its Pauli limit and about three times that of a simultaneously deposited reference film on $\mathrm{Si}/\mathrm{Si}{\mathrm{O}}_{2}$. The analysis of the ${H}_{c||}$ enhancement within the Maki theory indicates significant induced spin-orbit interaction in the Al due to electronic coupling to the TI. Our results revealed a pathway for producing SC/TI devices of high interfacial electrical transparency conducive for MZM generation and manipulation.