24,046 research outputs found
Topological phase transition from nodal to nodeless d-wave superconductivity in electron-doped cuprate superconductors
Unlike the hole-doped cuprates, both nodal and nodeless superconductivity
(SC) are observed in the electron-doped cuprates. To understand these two types
of SC states, we propose a unified theory by considering the two-dimensional
t-J model in proximity to an antiferromagnetic (AF) long-range ordering state.
Within the slave-boson mean-field approximation, the d-wave pairing symmetry is
still the most energetically favorable even in the presence of the external AF
field. In the nodal phase, it is found that the nodes carry vorticity and are
protected by the adjoint symmetry of time-reversal and one unit lattice
translation. Robust edge modes are obtained, suggesting the nodal d-wave SC
being a topological weak-pairing phase. As decreasing the doping concentration
or increasing the AF field, the nodes with opposite vorticity annihilate and
the nodeless strong-pairing phase emerges. The topological phase transition is
characterized by a critical point with anisotropic Bogoliubov quasiparticles,
and a universal understanding is thus established for all electron-doped
cuprates.Comment: 7 pages, 5 figures; published versio
The Effect of the One-Child Policy on Fertility in China: Identification Based on the Differences-in-Differences
This paper measures the effect of China's one-child policy on fertility by exploring the natural experiment that has been created by China's unique affirmative birth control policy, which is possibly the largest social experiment in human history. Because the one-child policy only applied to Han Chinese, but not to ethnic minorities, we construct a differences-in-differences estimator to identify the effect of the policy on fertility. Such a natural experiment is a rare opportunity, whether for the analysis of the effect on fertility or for the analysis of economics in general. Using two rounds of the Chinese Population Census, we find that the one-child policy has had a large effect on fertility. The average effect on the post-treatment cohorts on the probability of having a second child is as large as -11 percentage points. We also find that the magnitude is larger in urban areas and for more educated women. Our robustness tests suggest that our differences-in-differences estimates of the effect of the one-child policy are not very likely to be driven by other policy or socio-economic changes that have affected the Han and the minorities differently.
Study of weakly-bound odd-A nuclei with quasiparticle blocking
The coordinate-space Hartree-Fock-Bogoliubov (HFB) approach with
quasiparticle blocking has been applied to study the odd-A weakly bound nuclei
B and Mg, in which halo structures have been reported in
experiments. The Skyrme nuclear forces SLy4 and UNEDF1 have been adopted in our
calculations. The results with and without blocking have been compared to
demonstrate the emergence of deformed halo structures due to blocking effects.
In our calculations, B and Mg have remarkable features of
deformed halos.Comment: 7 pages, 4 figures, 1 tabl
Invisible Higgs Decay at the LHeC
The possibility that the 125 GeV Higgs boson may decay into invisible
non-standard-model (non-SM) particles is theoretically and phenomenologically
intriguing. In this letter we investigate the sensitivity of the Large Hadron
Electron Collider (LHeC) to an invisibly decaying Higgs, in its proposed high
luminosity running mode. We focus on the neutral current Higgs production
channel which offers more kinematical handles than its charged current
counterpart. The signal contains one electron, one jet and large missing
energy. With a cut-based parton level analysis, we estimate that if the
coupling is at its standard model (SM) value, then assuming an integrated
luminosity of 1\,\mbox{ab}^{-1} the LHeC with the proposed 60 GeV electron
beam (with polarization) and 7 TeV proton beam is capable of probing
at level. Good lepton
veto performance (especially hadronic veto) in the forward region is
crucial to the suppression of the dominant background. We also explicitly
point out the important role that may be played by the LHeC in probing a wide
class of exotic Higgs decay processes and emphasize the general function of
lepton-hadron colliders in precision study of new resonances after their
discovery in hadron-hadron collisions.Comment: 6 pages, 3 figures. Description of the backgrounds, analysis and
results is simplified. Results unchanged with respect to v2. References
update
Two-dimensional topological superconducting phases emerged from d-wave superconductors in proximity to antiferromagnets
Motivated by the recent observations of nodeless superconductivity in the
monolayer CuO grown on the BiSrCaCuO
substrates, we study the two-dimensional superconducting (SC) phases described
by the two-dimensional - model in proximity to an antiferromagnetic (AF)
insulator. We found that (i) the nodal d-wave SC state can be driven via a
continuous transition into a nodeless d-wave pairing state by the proximity
induced AF field. (ii) The energetically favorable pairing states in the strong
field regime have extended s-wave symmetry and can be nodal or nodeless. (iii)
Between the pure d-wave and s-wave paired phases, there emerge two
topologically distinct SC phases with (i) symmetry, i.e., the weak and
strong pairing phases, and the weak pairing phase is found to be a
topological superconductor protected by valley symmetry, exhibiting robust
gapless non-chiral edge modes. These findings strongly suggest that the
high- superconductors in proximity to antiferromagnets can realize fully
gapped symmetry protected topological SC.Comment: 7 pages, 4 figures; revised versio
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