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Superconductivity originates from the formation of bound (Cooper) pairs of electrons that can move through the lattice without resistance below the superconducting transition temperature T.sub.c (ref. .sup.1). Electron Cooper pairs in most superconductors form anti-parallel spin singlets with total spin S = 0 (ref. .sup.2), although they can also form parallel spin-triplet Cooper pairs with S = 1 and an odd parity wavefunction.sup.3. Spin-triplet pairing is important because it can host topological states and Majorana fermions relevant for quantum computation.sup.4,5. Because spin-triplet pairing is usually mediated by ferromagnetic (FM) spin fluctuations.sup.3, uranium-based materials near an FM instability are considered to be ideal candidates for realizing spin-triplet superconductivity.sup.6. Indeed, UTe.sub.2, which has a T.sub.c [almost equal to] 1.6 K (refs. .sup.7,8), has been identified as a candidate for a chiral spin-triplet topological superconductor near an FM instability.sup.7-14, although it also has antiferromagnetic (AF) spin fluctuations.sup.15,16. Here we use inelastic neutron scattering (INS) to show that superconductivity in UTe.sub.2 is coupled to a sharp magnetic excitation, termed resonance.sup.17-23, at the Brillouin zone boundary near AF order. Because the resonance has only been found in spin-singlet unconventional superconductors near an AF instability.sup.17-23, its observation in UTe.sub.2 suggests that AF spin fluctuations may also induce spin-triplet pairing.sup.24 or that electron pairing in UTe.sub.2 has a spin-singlet component. Inelastic neutron scattering measurements show that superconductivity in UTe.sub.2 is associated with a resonance near antiferromagnetic order that suggests an unexpected spin-singlet component to the electron pairing., Author(s): Chunruo Duan [sup.1] , R. E. Baumbach [sup.2] [sup.3] , Andrey Podlesnyak [sup.4] , Yuhang Deng [sup.5] , Camilla Moir [sup.5] , Alexander J. Breindel [sup.5] , M. Brian [...]

Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to investigate 1,2-dihydro-l,3.2-diazaborinine:HX complexes for HX = [H.sup.+], HF, HC1, [H.sub.2]O, HCN, [NH.sub.3], HCP, and HCCH. Most complexes are stabilized by linear, traditional hydrogen bonds except for those with [H.sub.2]O and [NH.sub.3], which have bridging structures and nonlinear hydrogen bonds. H-atom transfer from ? to ? can occur in complexes with HF and HC1, with formation of a traditional F-H***N bond and a protonshared CI--?--? bond. The binding energies of the uncharged complexes range from 25 to 88 kJ [mol.sup.-1]. Spin-spin coupling constants have been used to characterize these hydrogen-bonded complexes. Key words: diazaborinines, structures and binding energies, EOM-CCSD spin-spin coupling constants. Des calculs ab initio MP2/aug'-cc-pVTZ ont ete effectues pour etudier les complexes 1,2dihydro-l,3,2-diazaborinine:HX pour HX = FT, HF, HC1, [H.sub.2]O, HCN, [NH.sub.3], HCP et HCCH. La plupart des complexes sont stabilises par des liaisons hydrogene classiques lineaires, a 1'exception de celles avec [H.sub.2]O et [NH.sub.3], qui forment des structures en pontage et des liaisons hydrogene non lineaires. Le transfert de l'atome d'hydrogene de ? a B peut se produire dans des complexes avec HF et HC1, avec formation d'une liaison F-H-N classique et d'une liaison CI--?--? comportant un proton partage. Les energies de liaison des complexes non charges vont de 25 a 88 kJ [mol.sup.-1]. Des constantes de couplage spin-spin ont ete utilisees pour caracteriser ces complexes a liaison l'hydrogene. [Traduit par la Redaction] Mots-cles: diazaborinines, structures et energies de liaison, constantes de couplage spin-spin EOM-CCSD., 1. Introduction The element boron has a very rich chemistry insofar as it exhibits a variety of bonding patterns. (1) Boron is usually thought of as an electron deficient element [...]

Moiré superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moiré superlattices.sup.1-4. Transition metal dichalcogenide moiré heterostructures provide another model system for the study of correlated quantum phenomena.sup.5 because of their strong light-matter interactions and large spin-orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe.sub.2/WS.sub.2 moiré superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice.sup.6-11. Furthermore, the spin-valley optical selection rules.sup.12-14 of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Our studies highlight the value of using moiré superlattices beyond graphene to explore correlated physics. Strongly correlated insulating Mott and generalized Wigner phases are detected in WSe.sub.2/WS.sub.2 moiré superlattices, and their electrical properties and excited spin states are studied using an optical technique., Author(s): Emma C. Regan [sup.1] [sup.2] [sup.3] , Danqing Wang [sup.1] [sup.2] [sup.3] , Chenhao Jin [sup.1] [sup.4] , M. Iqbal Bakti Utama [sup.1] [sup.3] [sup.5] , Beini Gao [sup.1] [...]

We solve the (2+1)-dimensional Dirac oscillator in the presence of spin-orbit interaction within the framework of minimal length quantum mechanics. To report an exact analytical solution, we transform the problem into the momentum space and polar coordinates and thereby obtain the eigenfunctions and eigenenergies of the system. Key words: minimal length, generalized uncertainty principle, spin-orbit interaction, Dirac oscillator, analytical approach. Resume : Nous solutionnons l'oscillateur de Dirac en (2+1) dimensions, en presence d'interaction spin-orbite dans le cadre de la mecanique quantique a longueur elementaire. Afin de presenter une solution analytique, nous transformons le probleme dans l'espace des impulsions avec coordonnees polaires et obtenons ainsi les fonctions et energies propres du systeme. [Traduit par la Redaction] Mots-cles: longueur elementaire, principe d'incertitude generalise, interaction spin-orbite, oscillateur de Dirac, approche analytique. PACS Nos.: 03.65.Pm, 03.65.Ge, 12.90.+b., 1. Introduction The spin-orbit interaction (SOI) is an interaction of a particle's spin with its motion. The SOI yields shifts in the electron's energy due to electromagnetic interaction between the [...]

The potential energy curves of the molecule LiCs have been calculated for the 55 low-lying electronic states in the Ω-representation. Using an ab initio method the calculation is based on a nonempirical pseudo-potential in the interval 3.0 [a.sub.0] ≤ R ≤ 4 [a.sub.0] of the internuclear distance. The spin-orbit effects have been taken into account through a semi-empirical spin-orbit pseudo-potential added to the electrostatic Hamiltonian with Gaussian basis sets for both atoms. The spectroscopic constants have been calculated for 39 states and the components of the spin-orbit splitting have been identified for the states [(2, 5).sup.3]Π and [(1).sup.3]Δ. The comparison of the present results with those available in literature shows good agree ment, while the other results, to the best of our knowledge, are given here for the first time. PACS Nos: 31.15.Ar, 31.25.Nj, 31.50.Df, 33.20.Vq Nous avons calcule les courbes d'energie potentielle de la molecule LiCs pour les 55 premiers etats electroniques dans la representation Ω. Utilisant une methode ab initio, le calcul est base sur un pseudo-potential dans l'intervalle 3,0 [a.sub.0] ≤ R ≤ 40,0 [a.sub.0] de la distance internucleaire. Les effets de couplage spin-orbite sont pris en compte via un pseudo-potentiel spin-orbite empirique ajoute an Hamiltonien coulombien, avec un ensemble de base d'etats gaussiens pour les deux atomes. Les constantes spectroscopiques sont calcuaees pour 39 etats et les composantes de la separation spin-orbite sont identifiees pour les etats [(2, 5).sup.3]Π et [(1).sup.3]Δ. Ces resultats montre un bon accord avec ceux existant dans la litterature, alors que les autres sont, a notre connaissance, donnes pour la premiere fois. [Traduit par la Redaction], 1. Introduction Since the advent of laser cooling and trapping, ultracold molecules are a current and great challenge in the study of spectroscopy. Indeed, ultracold molecules allow the reinvestigation of [...]

We review the transformation properties of ELKO spinors (Eigenspinoren des Ladungskonjugationsoperators) under charge conjugation, parity, and time reversal. Our calculations confirm that ELKO spinors are not eigenspinors of the helicity operator and satisfy [(CPT).sup.2] = - which identifies them as a representation of a nonstandard Wigner class. However, we find that ELKO spinors transform symmetrically under parity instead of the previously assumed asymmetry. Furthermore, we demonstrate that ELKO spinors transform asymmetrically under time reversal, which is opposite to the previously reported symmetric behaviour. These changes affect the (anti)commutation relations that are satisfied by the operators acting on ELKO spinors. We are also able to show that ELKO spinors actually satisfy the same (anti)commutation relations as Dirac spinors, even though they belong to two different representations. PACS Nos: 04.20.Gz, 11.10.Lm, 11.30.Er, 95.30.Cq Nous passons en revue les proprietes des spineurs ELKO sous les transformation de conjugaison de charge, de parite et de renversement du temps. Nos calculs confirment que les spineurs ELKO ne sont pas des spineurs propres de l'operateur de helicity et qu'ils satisfont [(CPT).sup.2] = - ce qui les identifie comme une representation d'une classe non standard de Wigner. Cependant, nous trouvons que les spineurs ELKO se transforment symetriquement sous parite, alors qu'on les presumait asymetriques. Par contre, nous demontrons qu'ils se transforment de facon asymetrique sous renversement du temps, ici aussi l'inverse de ce qu'on croyait. Ces changements affectent les relations de (anti)commutation qui sont satisfaites par les operateurs agissant sur les spineurs ELKO. Nous sommes aussi capables de demontrer que les spineurs ELKO satisfont les mmes relations de (anti)commutation que les spineurs de Dirac, meme s'ils appartiennent a deux representations differentes. [Traduit par la Redaction], 1. Introduction The recent proposal of matter fields with spin one-half and mass dimension one, "Eigenspinoren des Ladungskonjugationsoperators" (ELKO) -- translating to eigenspinors of the charge conjugation operator -- opens [...]

The purpose of this paper is to use a new rational approach for the design of some magnetic couplings. Our method is based on the association of analytical models and an exact global optimization algorithm named IBBA and developed by the third author. The analytical model presented in this paper is more sophisticated than those previously dealt using IBBA. Therefore, some under and over estimating functions have been constructed for those particular problems of design in order to improve the convergence of IBBA. Some optimal results highlight the efficiency of this approach. Index Terms--Analytical model, Branch&Bound, exact global optimization, interval arithmetic, inverse problem, magnetic coupling.

Domain walls in ferromagnetic metals are known to be a source of resistance. We have studied the resistance resulting from a one-dimensional Neel-type magnetic domain wall in presence of Rashba spin-orbit coupling and external magnetic field. The analysis has been based on Boltzmann transport equation, within the relaxation time approximation. Through this formalism, we have shown that the spin-flip scattering and the resulting resistance originating from the Rashba spin-orbit coupling can be suppressed by the applied external magnetic field. Index Terms--Magnetic domain wall, magnetic field, resistance, spin-orbit interaction.

We report on the enhancement of the exchange field, [H.sub.EX], in IrMn/CoFe systems as a result of the application of field annealing procedures. The exchange field is enhanced up to a 37% on application of a 2 Tesla field for 90 minutes at 225[degrees]C. This setting process improves the magnitude of [H.sub.EX] without significant changes in the coercivity, [H.sub.C], or the median blocking temperature. The sample with largest exchange bias field measured, 3.7 kOe and [H.sub.c] = 0.2 kOe at 20[degrees]C, seems to have the largest ratio of [H.sub.EX] to [H.sub.C] ever reported for an IrMn/CoFe exchange bias system. This makes these structures good candidates as pinned layers in magnetic tunnel junctions. The samples show good thermal stability with median blocking temperatures up to 200[degrees]C. The results also indicate that the improvement in the quality of the interfaces via the degree of alignment of the interfacial spins improves the coupling across the interface and hence the magnitude of the exchange bias field. Index Terms--Blocking temperature, exchange bias, interfacial coupling, thermal activation.

We present theoretical and numerical studies of the magnetic anisotropy energy of an atomic-like impurity near the surface of a metallic host (Au). The valence band of the host metal is described in terms of a realistic tight-binding surface Green's function technique. We compare two models: (i) when spin-orbit coupling is taken into account in the d-band of the host and (ii) when the impurity's d-level experiences strong spin-orbit splitting. The level splitting of the impurity's spin-states is calculated in leading (first or second) order of the exchange interaction between the impurity and the host atoms. It is shown that the magnetic anisotropy constant is an oscillating function of the distance d of the impurity from the surface. For large distances, an asymptotic analysis implies that the period of these oscillations is determined by the extremal vectors of the host's Fermi Surface and the amplitude decays as 1/[d.sup.2]. Our numerical results dearly suggest that the host-induced magnetic anisotropy energy is by several orders smaller in magnitude than the one originating from a strong local spin-orbit coupling. Index Terms--Anisotropy impurity surface.

In the diffusive regime, the accumulated spins diffuse out symmetrically in both directions of the InAs channel and the spin signal exponentially decays with the distance. However, considering spin drift induced by the applied electrical current, the spin diffusion occurs in an asymmetric manner. Nonlocal measurements of a lateral spin-valve structure show that the amount of spin polarized electron depends on the direction of the electric field. The magnitude of the nonlocal signal difference due to the bias-current-induced drift effect diminishes from 5.6 m[ohm] at T = 20 K to close to zero at T = 300 K. Index Terms--Bias current, spin accumulation, spin diffusion, spin drift, two-dimensional electron gas.