4,979 research outputs found
Quantum phase transition in the one-dimensional period-two and uniform compass model
Quantum phase transition in the one-dimensional period-two and uniform
quantum compass model are studied by using the pseudo-spin transformation
method and the trace map method. The exact solutions are presented, the
fidelity, the nearest-neighbor pseudo-spin entanglement, spin and pseudo-spin
correlation functions are then calculated. At the critical point, the fidelity
and its susceptibility change substantially, the gap of pseudo-spin concurrence
is observed, which scales as (N is system size). The spin correlation
functions show smooth behavior around the critical point. In the period-two
chain, the pseudo-spin correlation functions exhibit a oscillating behavior,
which is absent in the unform chain. The divergent correlation length at the
critical point is demonstrated in the general trend for both cases.Comment: 5 pages, 6 figure
Dynamics of coherence, localization and excitation transfer in disordered nanorings
Self-assembled supramolecular aggregates are excellent candidates for the
design of efficient excitation transport devices. Both artificially prepared
and natural photosynthetic aggregates in plants and bacteria present an
important degree of disorder that is supposed to hinder excitation transport.
Besides, molecular excitations couple to nuclear motion affecting excitation
transport in a variety of ways. We present an exhaustive study of exciton
dynamics in disordered nanorings with long-range interactions under the
influence of a phonon bath and take the LH2 system of purple bacteria as a
model. Nuclear motion is explicitly taken into account by employing the Davydov
ansatz description of the polaron and quantum dynamics are obtained using a
time-dependent variational method. We reveal an optimal exciton-phonon coupling
that suppresses disorder-induced localization and facilitate excitation
de-trapping. This excitation transfer enhancement, mediated by environmental
phonons, is attributed to energy relaxation toward extended, low-energy
excitons provided by the precise LH2 geometry with anti-parallel dipoles and
long-range interactions. An analysis of localization and spectral statistics is
followed by dynamical measures of coherence and localization, transfer
efficiency and superradiance. Linear absorption, 2D photon-echo spectra and
diffusion measures of the exciton are examined to monitor the diffusive
behavior as a function of the strengths of disorder and exciton-phonon
coupling.Comment: 18 pages, 13 figure
Processing techniques of point cloud data on small-sized objects with complex free-form surface
The scattered point cloud data, which comes from such small-sized objects with complex free-form surface as shelled shrimp, is processed as error points removing, points filtering, holes filling, clouds segmenting, etc. using CATIA V5 R20. The principle of data processing and skills utilized in the operation mentioned above apply also to the small-sized objects similar to the shelled shrimp in reverse engineering in other fields, such as optical components, irregular parts, ears, nose, etc
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