Controllable chiral Majorana modes by noncollinear magnetic configuration in a topological Josephson junction

Recently, theory and experiment both have confirmed a Majorana zero mode to induce selective equal spin Andreev reflection (SESAR). Herein, we theoretically present controllable chiral Majorana modes (CMMs) by noncollinear magnetic configuration in a Josephson junction on a topological insulator with two ferromagnetic insulators (FIs) sandwiched in between two superconductors (SCs). It is shown that an additional phase shift is induced by the different chirality of the CMMs at the two FI/SC interfaces, whose magnitude is determined by misorientational angle θ, which can be administrated by the Andreev bound surface energies. The angle θ is found to result in the 0-π state transition and Φ0 supercurrent. Particularly, due to the SESAR, the coexistence of fully spin-polarized spin-singlet and -triplet correlations is exhibited with the exclusive fully spin-polarized spin-triplet (singlet) correlation corresponding to the ferromagnetic (F) [antiferromagnetic (AF)] configuration. For the two magnetizations only along y-axis, there exist no additional phase shift and topological supercurrent with fully spin-polarized correlations, especially, the supercurrent in the AF configuration is a lot larger than that in the F one, which is strongly dependent on the exchange field strength and FI length, thus even leading to 100% supercurrent magnetoresistance. The results can be employed to not only identify the topological SCs but also design a perfect topological supercurrent spin valve device.

Modulation of persistent current in graphene quantum rings

We investigate the effect of long-range impurity potentials on the persistent current of graphene quantum rings in the presence of an uniform perpendicular magnetic field. The impurity potentials are modeled as finite regions of the ring with a definite length. We show that, due to the relativistic and massless character of the charge carriers in graphene, the effect of such non-uniform potentials on the energy spectrum and on the persistent current of the rings can be reliably modeled by assuming a non-perturbed ring and including an additional phase due to the interaction of the charge carriers with the potential. In addition, the results show the presence of localized states in the impurity regions. Moreover, we show that for the case of a potential created by a p-n-p junction, the persistent current can be modulated by controlling the voltage at the junction.

The noncollinear phase-matching geometries in ultra-broadband quasi-parametric amplification

Optical parametric chirped pulse amplification (OPCPA) shows great potential in producing ultrashort high-intensity pulses because of its large gain bandwidth. Quasi-parametric chirped pulse amplification (QPCPA) may further extend the bandwidth, but the behavior of QPCPA at a limited pump intensity (e.g., ≤5 GW/cm2 in a nanosecond pumped QPCPA) is not fully investigated yet. We have discussed in detail the ultra-broadband amplification and the noncollinear phase-matching geometry in QPCPA. We have modeled and developed a novel noncollinear geometry in QPCPA namely ’triple-wavelength phase-matching geometry’ which provides two additional phase-matching points around the phase-matching point at the center wavelength. Our analysis demonstrates that the triple-wavelength phase-matching geometry can support stable, ultra-broadband amplification in QPCPA. The numerical simulation results show that ultrashort pulse with a pulse duration of 7.92 fs can be achieved in QPCPA when the pump intensity is limited to 5 GW/cm2, calculated using the nonlinear coefficient of YCOB.

A comparative study on properieties of hydroxyapatite prepared from bovine and dromedary bone

The recovery of agro-food waste is at the heart of the challenges of the 21st century, in this context that this research work comes. A biomaterial is prepared from a significant resource such as dromedary bone and bovine bone by heat treatment at different temperatures and characterized by physico-chemical techniques in order to have the effect of bone type on the physico-chemical properties of hydroxyapatite. The results of FTIR and DRX show the removal of all organic matter and the production of pure hydroxyapatite without any additional phase for both bone types. Analyzes by SEM and laser particle size analyzer show that the particle size of hydroxyapatite is increased with increasing temperature. From the results of XRF, bone type is a direct effect on the concentration of hydroxyapatite compounds in hydroxyapatite prepared from dromedary bone compared to hydroxyapatite prepared from bovine bone.

Multiferroic and Nanomechanical Properties of Bi1−xGdxFeO3 Polycrystalline Films (x = 0.00–0.15)

In this work, we adopted pulsed laser deposition (PLD) with a Nd:YAG laser to develop Bi1−xGdxFeO3 (BGFO) films on glass substrates. The phase composition, microstructure, ferroelectric, magnetic, and nanomechanical properties of BGFO films are studied. BGFO films with x = 0.00–0.15 were confirmed to mainly consist of the perovskite phase. The structure is transformed from rhombohedral for x = 0.00 to pseudo-cubic for x = 0.05–0.10, and an additional phase, orthorhombic, is coexisted for x = 0.15. With increasing Gd content, the microstructure and surface morphology analysis shows a gradual decrease in crystallite size and surface roughness. The hardness of 5.9–8.3 GPa, measured by nanoindentor, is mainly dominated by crystallized structure and grain size. Good ferroelectric properties are found for BGFO films with x =0.00–0.15, where the largest remanent polarization (2Pr) of 133.5 µC/cm2 is achieved for x = 0.10, related to low leakage and high BGFO(110) texture. The improved magnetic properties with the significant enhancement of saturation magnetization from 4.9 emu/cm3 for x = 0 to 23.9 emu/cm3 for x = 0.15 by Gd substitution is found and related to large magnetic moment of Gd3+ and suppressed spiral spin structure of G-type antiferromagnetism. Furthermore, we also discuss the mechanisms of leakage behavior as well as nanomechanical characterizations as a function of the Gd content.

Skyrmion control of Majorana states in planar Josephson junctions

Planar Josephson junctions provide a versatile platform, alternative to the nanowire-based geometry, for the generation of the Majorana bound states, due to the additional phase tunability of the topological superconductivity. The proximity induction of chiral magnetism and superconductivity in a two-dimensional electron gas showed remarkable promise to manipulate topological superconductivity. Here, we consider a Josephson junction involving a skyrmion crystal and show that the chiral magnetism of the skyrmions can create and control the Majorana bound states without the requirement of an intrinsic Rashba spin-orbit coupling. Interestingly, the Majorana bound states in our geometry are realized robustly at zero phase difference at the junction. The skyrmion radius, being externally tunable by a magnetic field or a magnetic anisotropy, brings a unique control feature for the Majorana bound states.

Ruppeiner geometry and thermodynamic phase transition of the black hole in massive gravity

The phase transition and thermodynamic geometry of a 4-dimensional AdS topological charged black hole in de Rham, Gabadadze and Tolley (dRGT) massive gravity have been studied. After introducing a normalized thermodynamic scalar curvature, it is speculated that its value is related to the interaction between the underlying black hole molecules if the black hole molecules exist. We show that there does exist a crucial parameter given in terms of the topology, charge, and massive parameters of the black hole, which characterizes the thermodynamic properties of the black hole. It is found that when the parameter is positive, the singlet large black hole phase does not exist for sufficient low temperature and there is a weak repulsive interaction dominating for the small black hole which is similar to the Reissner–Nordström AdS black hole; when the parameter is negative, an additional phase region describing large black holes also implies a dominant repulsive interaction. These constitute the distinguishable features of dRGT massive topological black hole from those of the Reissner–Nordström AdS black hole as well as the Van der Waals fluid system.

The Denial of Genocide in Srebrenica in the Context of Strengthening Neo-fascism and Relativization of the Holocaust in Europe

The denial of the 1995 genocide against Bosniaks in the UN security zone of Srebrenica, has continued uninterrupted for 25 years. This denial has taken various forms and manifestations during that time; from denying the extent and character of crimes and the number of victims, to not accepting relevant court verdicts and especially, ignoring the consequences of genocide. As time passes, we are beginning to get the impression that an additional phase to the denial of the genocide in Srebrenica has emerged, in which, through the glorification of convicted war criminals and their affirmation in society, genocide is affirmed as an acceptable procedure and activity. We believe that this 25-year period of persistent denial, and even celebration of the genocide in Srebrenica, largely corresponds to the strengthening of neo-fascist and right-wing ideas and movements in European countries, which has been accompanied by an increasingly louder denial and relativization of the Holocaust. In this paper, we intend to analyze the connection between these phenomena, because we believe that the ideas pedaled by deniers of the genocide in Srebrenica, are significantly suited to strengthening the neo-fascism and Holocaust denial and are using this atmosphere to intensify genocide denial against Bosniaks and yet paradoxically, affirm the genocide, by glorifying the convicted war criminals and their ideas.

Skyrmion Control of Majorana States in Planar Josephson Junctions

Planar Josephson junctions provide a versatile platform, alternative to the nanowire-based geometry, for the generation of the Majorana bound states, due to the additional phase tunability of the topological superconductivity. The proximity induction of chiral magnetism and superconductivity in a two-dimensional electron gas showed remarkable promises to manipulate topological superconductivity. Here, we consider a Josephson junction involving a skyrmion crystal and show that the chiral magnetism of the skyrmions can create and control the Majorana bound states without the requirement of an intrinsic Rashba spin-orbit coupling. Interestingly, the Majorana bound states in our geometry are realized robustly at zero phase difference at the junction. The skyrmion radius, being externally tunable by a magnetic field or a magnetic anisotropy, brings a unique control feature for the Majorana bound states.