Theory of Fano resonance in single molecule electroluminescence induced by a scanning tunneling microscope

The coupling between molecular exciton and gap plasmons plays a key role in single molecular electroluminescence induced by a scanning tunneling microscope (STM). But it has been difficult to clarify the complex experimental phenomena. By employing the nonequilibrium Green's function method, we propose a general theoretical model to understand the light emission spectrum from single molecule and gap plasmons from an energy transport point of view. The coherent interaction between gap plasmons and molecular exciton leads to a prominent Fano resonance in the emission spectrum. We analyze the dependence of the Fano line shape on the system parameters, based on which we provide a unified account of several recent experimental observations. Moreover, we highlight the effect of the tip-molecule electronic coupling on the spectrum, which has hitherto not been considered

The sssˉsˉss \bar s \bar s tetraquark states and the newly observed structure X(2239)X(2239) by BESIII Collaboration

We investigate the mass spectrum of the $ss \bar s \bar s$ tetraquark states within the relativized quark model. By solving the Schr\"{o}dinger-like equation with the relativized potential, the masses of the $S-$ and $P-$wave $ss \bar s \bar s$ tetraquarks are obtained. The screening effects are also taken into account. It is found that the observed resonant structure $X(2239)$ in the $e^+e^- \to K^+K^-$ process by BESIII Collaboration can be assigned as a $P-$wave $1^{--}$ $ss \bar s \bar s$ tetraquark state. Furthermore, the radiative transition and strong decay behaviors of this structure are also estimated, which can provide helpful information for future experimental searches.Comment: 7 pages, 2 figures. Add the strong decay behaviors. Version accepted by Chinese Physics

Interpretation of the newly observed Σb(6097)±\Sigma_b(6097)^{\pm} and Ξb(6227)−\Xi_b(6227)^- states as the PP-wave bottom baryons

The strong decays of the $P$-wave $\Sigma_b$, $\Xi_b'$ and $\Omega_b$ baryons are investigated with a constituent quark model in the $j$-$j$ coupling scheme. The results show that the newly observed $\Sigma_b(6097)$ and $\Xi_b(6227)$ states by the LHCb collaboration can be assigned as the $\lambda$-mode $P$-wave singly bottom baryons. Given the heavy quark symmetry, both the $\Sigma_b(6097)$ and $\Xi_b(6227)$ states favor the light spin $j=2$ states with spin-parity numbers $J^P=3/2^-$ or $J^P=5/2^-$. More $P$-wave singly bottom baryons are most likely to be observed in future experiments for their relatively narrow width.Comment: 7 pages. arXiv admin note: text overlap with arXiv:1709.0426

Entanglement and quantum superposition induced by a single photon

We predict the occurrence of single-photon-induced entanglement and quantum superposition in a hybrid quantum model, introducing an optomechanical coupling into the Rabi model. Originally, it comes from the photon-dependent quantum property of ground state featured by the proposed hybrid model. It associates with a single-photon-induced quantum phase transition, and is immune to the $A^2$ term of the spin-field interaction. Moreover, the obtained quantum superposition state is actual a squeezed cat state, which can give a significant precision enhancement in quantum metrology. This work offers an approach to manipulate entanglement and quantum superposition with a single photon, which might has potential applications in the engineering of new single-photon quantum devices, and also fundamentally broaden the regime of cavity QED.Comment: 7 pages, 5 figures, Published in Physical Review A 97, 033807 (2018). arXiv admin note: text overlap with arXiv:1803.0659

Non-thermal vibrations in biased molecular junctions

We study vibrational statistics in current-carrying model molecular junctions using master equation approach. Especially, we concentrate on the validity of using an effective temperature $T_{\rm eff}$ to characterize the nonequilibrium steady state of a vibrational mode. We identify cases where a single $T_{\rm eff}$ can not fully describe one vibrational state. In such cases, the probability distribution among different vibrational states does not follow the Boltzmann type. Consequently, the actual entropy (free energy) of the vibrational mode is lower (higher) than the corresponding thermal value given by $T_{\rm eff}$, indicating extra work can be extracted from these states. Our results will be useful for the study of non-thermal vibrational state in thermodynamics of nanoscale systems, and its usage in nanoscale heat engines

Mass spectra and radiative transitions of doubly heavy baryons in a relativized quark model

We study the mass spectra and radiative decays of doubly heavy baryons within the diquark picture in a relativized quark model. The mass of the $J^P=1/2^+$ $\Xi_{cc}$ ground state is predicted to be 3606 MeV, which is consistent with the mass of $\Xi_{cc}^{++}(3621)$ newly observed by the LHCb collaboration. The predicted mass gap between two $S$ wave states, $\Xi_{cc}^*$ ($J^P=3/2^+$) and $\Xi_{cc}$ ($J^P=1/2^+$), is 69 MeV. Furthermore, the radiative transitions of doubly heavy baryons are also estimated by using the realistic wave functions obtained from relativized quark model. The radiative decay widths of $\Xi_{cc}^{*++} \to \Xi_{cc}^{++}\gamma$ and $\Xi_{cc}^{*+} \to \Xi_{cc}^+\gamma$ are predicted to be about 7 and 4 keV, respectively. These predictions of doubly heavy baryons can provide helpful information for future experimental searches.Comment: 8 pages, 2 figure. The size effects of the diquarks are considered. Version accepted by Phys. Rev.

Nonequilibrium reservoir engineering of a biased coherent conductor for hybrid energy transport in nanojunctions

We show that a current-carrying coherent electron conductor can be treated as effective bosonic energy reservoir involving different types of electron-hole pair excitation. For weak electron-boson coupling, hybrid energy transport between nonequilibrium electrons and bosons can be described by a Landauer-like formula. This allows for unified account of a variety of heat transport problems in hybrid electron-boson systems. As applications, we study the non-reciprocal heat transport between electrons and bosons, thermoelectric current from a cold-spot and electronic cooling of the bosons. Our unified framework provides an intuitive way of understanding hybrid energy transport between electrons and bosons. It opens the way of nonequilibrium reservoir engineering for efficient energy control between different quasi-particles in the nanoscale

A Comprehensive Analysis of Fermi Gamma-ray Burst Data: II. EpE_{\rm p}-Evolution Patterns and Implications for the Observed Spectrum-Luminosity Relations

We present a time-resolved spectral analysis of 51 long and 11 short bright GRBs observed with the {\em Femri}/GBM, paying special attention to $E_{\rm p}$ evolution within a same burst. Among 8 single-pulse long GRBs, 5 show hard-to-soft evolution, while 3 show intensity-tracking. The multi-pulse long GRBs have more complicated patterns. Among the GRBs whose time-resolved spectrum is available for the first pulse, almost half (15/32 GRBs) show clear hard-to-soft evolution, and the other half (17/32 GRBs) show clear intensity-tracking. Later pulses typically show the tracking behavior, although a hard-to-soft evolution pattern was identified in the 2nd pulse of 2 GRBs whose pulses are well separated. Statistically, the hard-to-soft evolution pulses tend to be more asymmetric than the intensity-tracking ones, with a steeper rising wing than the falling wing. Short GRBs have $E_{\rm p}$ tracking intensity exclusively with the 16ms time resolution analysis. We performed a simulation analysis, and suggest that at least for some bursts, the late intensity-tracking pulses could be a consequence of overlapping hard-to-soft pulses. However, the fact that the intensity-tracking pattern exists in the first pulse of multi-pulse long GRBs and some single-pulse GRBs suggest that intensity tracking is an independent component, which may operate in some late pulses as well. For the GRBs with measured redshifts, we present a time-resolved $E_{\rm p}-L_{\gamma, \rm iso}$ correlation analysis and show that the scatter of the correlation is comparable to that of the global Amati/Yonetoku relation. We discuss the predictions of various radiation models regarding $E_{\rm p}$ evolution, as well as the possibility of a precession jet in GRBs. It seems that the data pose great challenge to all these models, and hold the key to unveil the physics of GRB prompt emission.Comment: 9 figures and 1 table. Accepted for publication in The Astrophysical Journa

CPCP violation for B0→ρ0(ω)ρ0(ω)→π+π−π+π−B^{0}\rightarrow \rho^{0}(\omega)\rho^{0}(\omega) \rightarrow \pi^+\pi^-\pi^+\pi^- in QCD factorization

In the QCD factorization (QCDF) approach we study the direct $CP$ violation in $\bar{B}^{0}\rightarrow\rho^0(\omega)\rho^0(\omega)\rightarrow\pi^+\pi^-\pi^+\pi^-$ via the $\rho-\omega$ mixing mechanism. We find that the $CP$ violation can be enhanced by double $\rho-\omega$ mixing when the masses of the $\pi^+\pi^-$ pairs are in the vicinity of the $\omega$ resonance, and the maximum $CP$ violation can reach 28{\%}. We also compare the results from the naive factorization and the QCD factorization.Comment: arXiv admin note: text overlap with arXiv:0805.0329, arXiv:1010.3309 by other author

Diagnosing the remnants of binary neutron star merger from GW170817/GRB170817A event

The event GW170817/GRB 170817A, discovered via the successful joint observation of its gravitational wave radiation and its multi-wavelength electromagnetic counterparts, was the first definite "smoking-gun" from the merger of two neutron stars (NSs). However, the remnant of the merger remains unknown. Piro et al. recently claimed that a low-significance X-ray variability in GRB 170817A. By systematically comparing the properties of variability in the afterglow of GRB 170817A and X-ray flares in GRB afterglows, we find that this X-ray variability seems to share similar statistical correlations with X-ray flares in GRB afterglows. We further investigate several possible merger product scenarios to see whether they can produce the observed X-ray variability in GRB 170817A. The first scenario invokes a stable magnetar as the central engine producing the later X-ray variability via differential rotation or fall-back accretion onto the NS. The second scenario invokes a black hole as the central engine with a fall-back accretion process. The final scenario is a central engine with a long-lived supra-massive NS. We find that the first two scenarios have difficulty producing the later X-ray variability, which requires either an impractical NS magnetic field or an extraordinarily large stellar envelope and an extremely long accretion timescale. However, the third scenario seems to be consistent with observations, and the later X-ray variability can be produced by the magnetosphere which is expelled following the collapse of the NS with a $B_p\in(3.6, 13.5)\times10^{13}$ G.Comment: 7 pages, 2 figures. Accepted for publication in MNRA