Signatures of Majorana Kramers pairs in superconductor-Luttinger liquid and superconductor-quantum dot-normal lead junctions

Time-reversal invariant topological superconductors are characterized by the presence of Majorana Kramers pairs localized at defects. One of the transport signatures of Majorana Kramers pairs is the quantized differential conductance of $4e^2/h$ when such a one-dimensional superconductor is coupled to a normal-metal lead. The resonant Andreev reflection, responsible for this phenomenon, can be understood as the boundary condition change for lead electrons at low energies. In this paper, we study the stability of the Andreev reflection fixed point with respect to electron-electron interactions in the Luttinger liquid. We first calculate the phase diagram for the Luttinger liquid-Majorana Kramers pair junction and show that its low-energy properties are determined by Andreev reflection scattering processes in the spin-triplet channel, i.e. the corresponding Andreev boundary conditions are similar to that in a spin-triplet superconductor - normal lead junction. We also study here a quantum dot coupled to a normal lead and a Majorana Kramers pair and investigate the effect of local repulsive interactions leading to an interplay between Kondo and Majorana correlations. Using a combination of renormalization group analysis and slave-boson mean-field theory, we show that the system flows to a new fixed point which is controlled by the Majorana interaction rather than the Kondo coupling. This Majorana fixed point is characterized by correlations between the localized spin and the fermion parity of each spin sector of the topological superconductor. We investigate the stability of the Majorana phase with respect to Gaussian fluctuations.Comment: 26 pages, 8 figure

Tensorial form and matrix elements of the relativistic nuclear recoil operator

Within the lowest-order relativistic approximation ($\sim v^2/c^2$) and to first order in $m_e/M$, the tensorial form of the relativistic corrections of the nuclear recoil Hamiltonian is derived, opening interesting perspectives for calculating isotope shifts in the multiconfiguration Dirac-Hartree-Fock framework. Their calculation is illustrated for selected Li-, B- and C-like ions. The present work underlines the fact that the relativistic corrections to the nuclear recoil are definitively necessary for getting reliable isotope shift values.Comment: 22 pages, no figures, submitted to J. Phys.

Theoretical Studies of Spectroscopic Properties of the Cm+4 and Am+3

In this paper we report on large-scale multiconfiguration Hartree-Fock and multiconfiguration Dirac-Fock calculations of the fine structures of the Cm4+ and Am3+ ions, both having nominal 5f6 electronic configuration. Correlation effects play an extremely important role for both considered ions, and the single-configuration model is proved to be unfit to account for this complex picture. A comparison of the calculated energy levels with the results of spectroscopic measurements shows that theory and experiment are in quantitatively good agreement; the ground state of both ions is predicted to have nonmagnetic character. The accuracy of the results is estimated and discussed.JRC.E.6-Actinides researc

Correlation, Relativistic and Quantum Electrodynamics Effects on the Atomic Structure of eka-Thorium

Large-scale multiconguration Dirac-Fock calculations have been performed for the superheavy element eka-Thorium, Z = 122. The resulting atomic structure is compared with that obtained by various computational approaches involving dierent degrees of approximation, in order to elucidate the role that correlation, relativistic, Breit and Quantum Electrodynamics (QED) corrections play in determining the low-energy atomic spectrum. The accuracy of the calculations is assessed by comparing theoretical results obtained for Thorium with available experimental data.JRC.E.6-Actinides researc

The Role of Atomic Correlations in the Theoretical Study of Minor Actinide Ions

This paper aims to demonstrate the recent possibilities to account for correlation and relativistic effects in studying the electronic structure and energy spectra of actinide ions. The fine structure of lowest term 7F of tetravalent curium (Cm4+) is considered as an example, as part of an ongoing project to understand the unexpected ground-state properties of this peculiar ion. The calculations were performed in multiconfiguration Hartree¿Fock (including relativistic effects in the Breit¿Pauli approach) and multiconfuguration Dirac¿Fock approximations. The results obtained demonstrate that, whilst core¿valence and core¿ core correlations are essential to assess correctly the Cm4+ term energy, their role in the determination of the fine structure is much less important compared to that of valence¿valence correlations.JRC.E.6-Actinides researc