Beating maps of singlet fission: Full-quantum simulation of coherent two-dimensional electronic spectroscopy in organic aggregates

The coherent two-dimensional (2D) electronic spectra with respect to the singlet fission (SF) process in organic molecular aggregates are simulated by the Davydov ansatz combined with the Frenkel-Dirac time-dependent variational algorithm. By virtue of the full-quantum dynamical approach, we are able to identify the signals of triplet excitation in the excite-state absorption contribution of the 2D spectra. In order to discuss whether a mediative charge-transfer (CT) state is necessary to SF, we increase the CT-state energy and find, in a theoretical manner, the beating signal related to the triplet is inhibited. The vibronic coherence is then studied in the beating maps for both the ground and excited state. Except for the normal beating modes adhering to the relevant electronic state, we observe signals that are explicitly related to the triplet excitations. The pathways of transition corresponding to these signals are clarified in the respective Feynman diagram, which can help the experimenters determine the physical origin of relevant measurements.Comment: 10 pages, 5 figure

Steady state current fluctuations and dynamical control in a nonequilibrium single-site Bose-Hubbard system

We investigate nonequilibrium energy transfer in a single-site Bose-Hubbard model coupled to two thermal baths. By including a quantum kinetic equation combined with full counting statistics, we investigate the steady state energy flux and noise power. The influence of the nonlinear Bose-Hubbard interaction on the transfer behaviors is analyzed, and the nonmonotonic features are clearly exhibited. Particularly, in the strong on-site repulsion limit, the results become identical with the nonequilibrium spin-boson model. We also extend the quantum kinetic equation to study the geometric-phase-induced energy pump. An interesting reversal behavior is unraveled by enhancing the Bose-Hubbard repulsion strength.Comment: 12 pages,6 figure

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 $1/N$ (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

Negative differential thermal conductance and heat amplification in a nonequilibrium triangle-coupled spin-boson system at strong coupling

We investigate the nonequilibrium quantum heat transfer in a triangle-coupled spin-boson system within a three-terminal setup. By including the nonequilibrium noninteracting blip approximation approach combined with the full counting statistics, we analytically obtain the steady state populations and heat currents. The negative differential thermal conductance and giant heat amplification factor are clearly observed at strong qubit-bath coupling. %and the heat amplification is dramatically suppressed in the moderate coupling regime. Moreover, the strong interaction between the gating qubit and gating thermal bath is unraveled to be compulsory to exhibit these far-from equilibrium features.Comment: 9 pages, 6 figure

Searching for lepton flavor violating decays tau to Pl in Minimal R-symmetric Supersymmetric Standard Model

We analyze the lepton flavor violating decays $\tau\rightarrow Pl$ ($P=\pi,\eta,\eta';\;l=e,\mu$) in the scenario of the minimal R-symmetric supersymmetric standard model. The prediction on the branching ratios BR$(\tau\rightarrow P e)$ and BR$(\tau\rightarrow P \mu)$ is affected by the mass insertion parameters $\delta^{13}$ and $\delta^{23}$, respectively. These parameters are constrained by the experimental bounds on the branching ratios BR($\tau\rightarrow e (\mu) \gamma$) and BR($\tau\rightarrow 3e(\mu)$). The result shows $Z$ penguin dominates the prediction on BR($\tau\rightarrow Pl$) in a large region of the parameter space. The branching ratios for BR($\tau\rightarrow Pl$) are predicted to be, at least, five orders of magnitude smaller than present experimental bounds and three orders of magnitude smaller than future experimental sensitivities.Comment: 19 pages, 9 figures. arXiv admin note: text overlap with arXiv:2004.1226

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