We show that the surface of an $s$-wave superconductor decorated with a two-dimensional lattice of magnetic impurities can exhibit chiral topological superconductivity. If impurities order ferromagnetically and the superconducting surface supports a
sufficiently strong Rashba-type spin-orbit coupling, Shiba sub-gap states at impurity locations can hybridize into Bogoliubov bands with non-vanishing, sometimes large, Chern number $C$. This topological superconductor supports $C$ chiral Majorana edge modes. We construct phase diagrams for model two-dimensional superconductors, accessing the dilute and dense magnetic impurity limits analytically and the intermediate regime numerically. To address potential experimental systems, we identify stable configurations of ferromagnetic iron atoms on the Pb (111) surface and conclude that ferromagnetic adatoms on Pb surfaces can provide a versatile platform for two-dimensional topological superconductivity.
Recent experiments have provided evidence that one-dimensional (1D) topological superconductivity can be realized experimentally by placing transition metal atoms that form a ferromagnetic chain on a superconducting substrate. We address some propert
ies of this type of systems by using a Slater-Koster tight-binding model. We predict that topological superconductivity is nearly universal when ferromagnetic transition metal chains form straight lines on superconducting substrates and that it is possible for more complex chain structures. The proximity induced superconducting gap is $sim Delta E_{so} / J$ where $Delta$ is the $s$-wave pair-potential on the chain, $E_{so}$ is the spin-orbit splitting energy induced in the normal chain state bands by hybridization with the superconducting substrate, and $J$ is the exchange-splitting of the ferromagnetic chain $d$-bands. Because of the topological character of the 1D superconducting state, Majorana end modes appear within the gaps of finite length chains. We find, in agreement with experiment, that when the chain and substrate orbitals are strongly hybridized, Majorana end modes are substantially reduced in amplitude when separated from the chain end by less than the coherence length defined by the $p$-wave superconducting gap. We conclude that Pb is a particularly favorable substrate material for ferromagnetic chain topological superconductivity because it provides both strong $s-$wave pairing and strong Rashba spin-orbit coupling, but that there is an opportunity to optimize properties by varying the atomic composition and structure of the chain. Finally, we note that in the absence of disorder a new chain magnetic symmetry, one that is also present in the crystalline topological insulators, can stabilize multiple Majorana modes at the end of a single chain.
We present INTEGRAL spectral analysis in the orbital/superorbital phase space of LS I +61 303. A hard X-ray spectrum with no cutoff is observed at all orbital/superorbital phases. The hard X-ray index is found to be uncorrelated with the radio index
(non-simultaneously) measured at the same orbital and superorbital phases. In particular, the absence of an X-ray spectrum softening during the periods of negative radio index does not favor a simple interpretation of the radio index variations in terms of changes of state in a microquasar. We uncover hints for the superorbital variability in the hard X-ray flux, in phase with the superorbital modulation in soft X-rays. An orbital phase drift of radio peak flux and index along the superorbital period is observed in the radio data. We explore its influence on a previously reported double peak structure of radio orbital lightcurve, posing it as a plausible explanation.
Despite numerous mass extinctions in the Phanerozoic eon, the overall trend in biodiversity evolution was not blocked and the life has never been wiped out. Almost all possible catastrophic events (large igneous province, asteroid impact, climate cha
nge, regression and transgression, anoxia, acidification, sudden release of methane clathrate, multi-cause etc.) have been proposed to explain the mass extinctions. However, we should, above all, clarify at what timescale and at what possible levels should we explain the mass extinction? Even though the mass extinctions occurred at short-timescale and at the species level, we reveal that their cause should be explained in a broader context at tectonic timescale and at both the molecular level and the species level. The main result in this paper is that the Phanerozoic biodiversity evolution has been explained by reconstructing the Sepkoski curve based on climatic, eustatic and genomic data. Consequently, we point out that the P-Tr extinction was caused by the tectonically originated climate instability. We also clarify that the overall trend of biodiversification originated from the underlying genome size evolution, and that the fluctuation of biodiversity originated from the interactions among the earths spheres. The evolution at molecular level had played a significant role for the survival of life from environmental disasters.
We present timing, spectral, and long-term temporal analysis of the high mass X-ray binary (HMXB) 4U 1036-56 using INTEGRAL and Swift observations. We show that it is a weak hard X-ray source spending a major fraction of the time in quiescence, and o
nly occasionally characterized by X-ray outbursts. The outburst activity we report here lasts several days, with a dynamic range spanned by the luminosity in quiescence and in outburst as high as ~30. We report the detection of pulse period at 854.75+/-4.39 s during an outburst, which is consistent with previous measurements. Finally, we analyze the possibility of 4U 1036--56s association with the unidentified transient gamma-ray sources AGL J1037--5708 & GRO J1036--55, as prompted by its positional correlation.
IGR J18179-1621 is a hard X-ray binary transient discovered recently by INTEGRAL. Here we report on detailed timing and spectral analysis on IGR J18179-1621 in X-rays based on available INTEGRAL and Swift data. From the INTEGRAL analysis, IGR J18179-
1621 is detected with a significance of 21.6 sigma in the 18-40 keV band by ISGRI and 15.3 sigma in the 3-25 keV band by JEM-X, between 2012-02-29 and 2012-03-01. We analyze two quasisimultaneous Swift ToO observations. A clear 11.82 seconds pulsation is detected above the white noise at a confidence level larger than 99.99%. The pulse fraction is estimated as 22+/-8% in 0.2-10 keV. No sign of pulsation is detected by INTEGRAL/ISGRI in the 18-40 keV band. With Swift and INTEGRAL spectra combined in soft and hard X-rays, IGR J18179-1621 could be fitted by an absorbed power law with a high energy cutoff plus a Gaussian absorption line centered at 21.5 keV. An additional absorption intrinsic to the source is found, while the absorption line is evidence for most probably originated from cyclotron resonant scattering and suggests a magnetic field in the emitting region of sim 2.4 times 10^12 Gauss.
The classification of life should be based upon the fundamental mechanism in the evolution of life. We found that the global relationships among species should be circular phylogeny, which is quite different from the common sense based upon phylogene
tic trees. The genealogical circles can be observed clearly according to the analysis of protein length distributions of contemporary species. Thus, we suggest that domains can be defined by distinguished phylogenetic circles, which are global and stable characteristics of living systems. The mechanism in genome size evolution has been clarified; hence main component questions on C-value enigma can be explained. According to the correlations and quasi-periodicity of protein length distributions, we can also classify life into three domains.
There is an intrinsic relationship between the molecular evolution in primordial period and the properties of genomes and proteomes of contemporary species. The genomic data may help us understand the driving force of evolution of life at molecular l
evel. In absence of evidence, numerous problems in molecular evolution had to fall into a twilight zone of speculation and controversy in the past. Here we show that delicate structures of variations of genomic base compositions and amino acid frequencies resulted from the genetic code evolution. And the driving force of evolution of life also originated in the genetic code evolution. The theoretical results on the variations of amino acid frequencies and genomic base compositions agree with the experimental observations very well, not only in the variation trends but also in some fine structures. Inversely, the genomic data of contemporary species can help reconstruct the genetic code chronology and amino acid chronology in primordial period. Our results may shed light on the intrinsic mechanism of molecular evolution and the genetic code evolution.
Much evolutionary information is stored in the fluctuations of protein length distributions. The genome size and non-coding DNA content can be calculated based only on the protein length distributions. So there is intrinsic relationship between the c
oding DNA size and non-coding DNA size. According to the correlations and quasi-periodicity of protein length distributions, we can classify life into three domains. Strong evidences are found to support the order in the structures of protein length distributions.
We show that the holographic principle in quantum gravity imposes a strong constraint on life. The degrees of freedom of an organism can be estimated according to the theory of Boolean networks, which is constrained by the entropy bound. Hence we can
explain the languages in protein sequences or in DNA sequences. The overall evolution of biological complexity can be illustrated. And some general properties of protein length distributions can be explained by a linguistic mechanism.
