9,406 research outputs found
Higgs amplitude mode in massless Dirac fermion systems
The Higgs amplitude mode in superconductors is the condensed matter analogy
of Higgs bosons in particle physics. We investigate the time evolution of Higgs
amplitude mode in massless Dirac systems, induced by a weak quench of an
attractive interaction. We find that the Higgs amplitude mode in the
half-filling honeycomb lattice has a logarithmic decaying behaviour,
qualitatively different from the decay in the normal
superconductors. Our study is also extended to the doped cases in honeycomb
lattice. As for the 3D Dirac semimetal at half filling, we obtain an undamped
oscillation of the amplitude mode. Our finding is not only an important
supplement to the previous theoretical studies on normal fermion systems, but
also provide an experimental signature to characterize the superconductivity in
2D or 3D Dirac systems.Comment: 6 pages, 8 figure
Bounds for eigenvalue ratios of the Laplacian
For a bounded domain with a piecewise smooth boundary in an
-dimensional Euclidean space , we study eigenvalues of the
Dirichlet eigenvalue problem of the Laplacian. First we give a general
inequality for eigenvalues of the Laplacian. As an application, we study lower
order eigenvalues of the Laplacian and derive the ratios of lower order
eigenvalues of the Laplacian.Comment: 14 page
Study on the techniques of sustainable control of pine wood nematode disease (Bursaphelenchus xylophilus)
Optimal measurements to access classical correlations of two-qubit states
We analyze the optimal measurements accessing classical correlations in
arbitrary two-qubit states. Two-qubit states can be transformed into the
canonical forms via local unitary operations. For the canonical forms, we
investigate the probability distribution of the optimal measurements. The
probability distribution of the optimal measurement is found to be centralized
in the vicinity of a specific von Neumann measurement, which we call the
maximal-correlation-direction measurement (MCDM). We prove that for the states
with zero-discord and maximally mixed marginals, the MCDM is the very optimal
measurement. Furthermore, we give an upper bound of quantum discord based on
the MCDM, and investigate its performance for approximating the quantum
discord.Comment: 8 pages, 3 figures, version accepted by Phys. Rev.
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