20,221 research outputs found
Lower Bounds of Concurrence for Multipartite States
We study the entanglement of multipartite quantum states. Some lower bounds
of the multipartite concurrence are reviewed. We further present more effective
lower bounds for detecting and qualifying entanglement, by establishing
functional relations between the concurrence and the generalized partial
transpositions of the multipartite systems.Comment: 13 page
Measuring dark matter-neutrino relative velocity on cosmological scales
We present a new method to measure neutrino masses using the dark
matter-neutrino relative velocity. The relative motion between dark matter and
neutrinos results in a parity-odd bispectrum which can be measured from
cross-correlation of different cosmic fields. This new method is not affected
by most systematics which are parity even and not limited by the knowledge of
optical depth to the cosmic microwave background. We estimate the detectability
of the relative velocity effect and find that the minimal sum of neutrino
masses could be detected at high significance with upcoming surveys.Comment: 6 pages, 2 figures, 1 table, published versio
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
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