Superconducting Proximity Effect in Magnetic Molecules

<p>We studied the transport through magnetic molecules (MM) coupled to superconducting (S), ferromagnetic (F) and normal (N) leads, with the aim of investigating the interplay between the magnetism and the superconducting proximity effect. The magnetic molecules were modeled using the Anderson model with an exchange coupling between the electron spins and the spin of the molecule. We worked in the infinite superconducting gap limit and treated the coupling between the molecule and the superconducting lead exactly, via an effective Hamiltonian. For the F/N-MM-S systems we used a real-time diagrammatic perturbation theory to calculate the electronic transport properties of the systems to first order in the tunnel coupling to the normal or ferromagnetic lead and then analysed the properties with respect to the parameters of these models. For these systems we found that the current maps out the excitation energies of the eigenstates of the effective Hamiltonian and that various parameters in these systems can lead to a negative differential conductance. In the N-MM-S case the current had no overall spin dependence, but when the normal lead is instead ferromagnetic there was a spin dependence and both the electronic and molecular spin expectation values could take on non-zero values. We also found that the polarisation of the ferromagnetic lead suppresses the superconducting proximity effect. Furthermore in the N-MM-S case the Fano factor indicated a transition from Poissonian transport of single electrons to Poissonian transport of electron pairs as the superconducting proximity effect goes out of resonance, however in the F-MM-S case this did not occur. For the S-MM-S systems we calculated the equilibrium Josephson current and found that in the infinite superconducting gap limit no 0 − π transition was possible. Advantages of this study compared to related ones are that we allow for arbitrarily large Coulomb interactions and we take into account coupling to the superconducting lead non-perturbatively. This is however at the expense of working in the superconducting gap limit. Recently it has been possible to couple single molecules to superconducting leads. This study therefore aims to be indicative of the transport properties that will be observed in future experiments involving single magnetic molecules coupled to leads.</p>

Superconducting Proximity Effect in Magnetic Molecules

<p>We studied the transport through magnetic molecules (MM) coupled to superconducting (S), ferromagnetic (F) and normal (N) leads, with the aim of investigating the interplay between the magnetism and the superconducting proximity effect. The magnetic molecules were modeled using the Anderson model with an exchange coupling between the electron spins and the spin of the molecule. We worked in the infinite superconducting gap limit and treated the coupling between the molecule and the superconducting lead exactly, via an effective Hamiltonian. For the F/N-MM-S systems we used a real-time diagrammatic perturbation theory to calculate the electronic transport properties of the systems to first order in the tunnel coupling to the normal or ferromagnetic lead and then analysed the properties with respect to the parameters of these models. For these systems we found that the current maps out the excitation energies of the eigenstates of the effective Hamiltonian and that various parameters in these systems can lead to a negative differential conductance. In the N-MM-S case the current had no overall spin dependence, but when the normal lead is instead ferromagnetic there was a spin dependence and both the electronic and molecular spin expectation values could take on non-zero values. We also found that the polarisation of the ferromagnetic lead suppresses the superconducting proximity effect. Furthermore in the N-MM-S case the Fano factor indicated a transition from Poissonian transport of single electrons to Poissonian transport of electron pairs as the superconducting proximity effect goes out of resonance, however in the F-MM-S case this did not occur. For the S-MM-S systems we calculated the equilibrium Josephson current and found that in the infinite superconducting gap limit no 0 − π transition was possible. Advantages of this study compared to related ones are that we allow for arbitrarily large Coulomb interactions and we take into account coupling to the superconducting lead non-perturbatively. This is however at the expense of working in the superconducting gap limit. Recently it has been possible to couple single molecules to superconducting leads. This study therefore aims to be indicative of the transport properties that will be observed in future experiments involving single magnetic molecules coupled to leads.</p>

Classical potential for general spinning bodies

In this paper we compute the spin-dependent terms of the gravitational potential for general spinning bodies at the leading Newton’s constant G and to all orders in spin. We utilize the on-shell approach, which extracts the classical potential directly from the scattering amplitude. For spinning particles, extra care is required due to the fact that the spin space of each particle is independent. Once the appropriate matching procedures are applied, taking the classical-spin limit we obtain the potential for general spinning bodies. When the Wilson coefficients are set to unity, we successfully reproduced the potential for the Kerr black hole. Interestingly, for finite spins, we find that the finite-spin deviations from Kerr Wilson coefficients cancel with that in the matching procedure, reproducing the Kerr potential without the need for taking the classical-spin limit. Finally, we find that when cast into the chiral basis, the spin-dependence of minimal coupling exhibits factorization, allowing us to take the classical-spin limit straight forwardly.

On Spin dependence of the Fundamental Plane of black hole activity

ABSTRACT The Fundamental Plane (FP) of black hole (BH) activity in galactic nuclei relates X-ray and radio luminosities to BH mass and accretion rate. However, there is a large scatter exhibited by the data, which motivated us for a new variable. We add BH spin as a new variable and estimate the spin dependence of the jet power and disc luminosity in terms of radio and X-ray luminosities. We assume the Blandford–Znajek process as the main source of the outflow, and find that the jet power depends on BH spin stronger than quadratically at moderate and large spin values. We perform a statistical analysis for 10 active galactic nuclei (AGNs) which have sub-Eddington accretion rates and whose spin values are measured independently via the reflection or continuum-fitting methods, and find that the spin-dependent relation describes the data significantly better. This analysis, if supported with more data, could imply not only the spin dependence of the FP relation, but also the Blandford–Znajek process in AGN jets.

Properties of exotic nuclei and their linkage to the nucleonic interaction

The structure of exotic nuclei sheds new light on the linkage of the nuclear structure to the nucleonic interaction. The self-consistent mean-field (SCMF) theories are useful to investigate this linkage, which are applicable to many nuclei covering almost the whole range of the nuclear chart without artificial truncation of model space. For this purpose, it is desired to develop effective interaction for the SCMF calculations well connected to the bare nucleonic interaction. Focusing on ground-state properties, I show the results of SCMF calculations primarily with the Michigan-three-range-Yukawa (M3Y)-type semi-realistic interaction, M3Y-P6 and M3Y-P6a to be precise, and discuss in detail how the nucleonic interaction affects the structure of nuclei including those far off the [Formula: see text]-stability. The central channels of the effective interaction are examined by the properties of the infinite nuclear matter up to the spin dependence and the isospin dependence. While experimental information of the infinite matter is obtained by extrapolating systematic data on finite nuclei in principle, it is not easy to constrain the spin dependence and the isospin dependence without connection to the bare nucleonic interaction. The noncentral channels play important roles in the shell structure of the finite nuclei. The tensor force is demonstrated to affect [Formula: see text]- or [Formula: see text]-dependence of the shell structure and the magic numbers, on which the spin–isospin channel in the central force often acts cooperatively. By using the M3Y-P6 interaction, the prediction of magic numbers is given in a wide range of the nuclear chart, which is consistent with almost all the available data. In relation to the erosion of magic numbers in unstable nuclei, effects of the tensor force on the nuclear deformation are also argued, being opposite between nuclei at the [Formula: see text]- and the [Formula: see text]-closed magicities. Qualitatively consistent with the [Formula: see text]-force effect on the [Formula: see text]-splitting suggested from the chiral effective field theory, the density-dependent LS channel, which is newly introduced in M3Y-P6a, reproduces the observed kinks in the differential charge radii at the [Formula: see text]-closed magic numbers and predicts anti-kinks at the [Formula: see text]-closed magic numbers. The pairing correlation has significant effects on the halos near the neutron drip line. A new mechanism called “unpaired-particle haloing” is disclosed.