Topological Floquet-bands in a circularly shaken dice lattice

The hoppings of non-interacting particles in the optical dice lattice result in the gapless dispersions in the band structure formed by the three lowest minibands. In our research, we find that once a periodic driving force is applied to this optical dice lattice, the original spectral characteristics could be changed, forming three gapped quasi-energy bands in the quasi-energy Brillouin zone. The topological phase diagram containing the Chern number of the lowest quasi-energy band shows that when the hopping strengths of the nearest-neighboring hoppings are isotropic, the system persists in the topologically non-trivial phases with Chern number $C=2$ within a wide range of the driving strength. Accompanied by the anisotropic nearest-neighboring hopping strengths, a topological phase transition occurs, making Chern number change from $C=2$ to $C=1$. This transition is further verified by our analytical method. Our theoretical work implies that it is feasible to realize the non-trivially topological characteristics of optical dice lattices by applying the periodic shaking, and that topological phase transition can be observed by independently tuning the strength of a type of nearest-neighbor hopping.Comment: 11 pages, 5 figure

Power law hopping of single particles in one-dimensional non-Hermitian quasicrystals

In this paper, a non-Hermitian Aubry-Andr\'e-Harper model with power-law hoppings ($1/s^{a}$) and quasiperiodic parameter $\beta$ is studied, where $a$ is the power-law index, $s$ is the hopping distance, and $\beta$ is a member of the metallic mean family. We find that under the weak non-Hermitian effect, there preserves $P_{\ell=1,2,3,4}$ regimes where the fraction of ergodic eigenstates is $\beta$-dependent as $\beta^{\ell}$L ($L$ is the system size) similar to those in the Hermitian case. However, $P_{\ell}$ regimes are ruined by the strong non-Hermitian effect. Moreover, by analyzing the fractal dimension, we find that there are two types of edges aroused by the power-law index $a$ in the single-particle spectrum, i.e., an ergodic-to-multifractal edge for the long-range hopping case ($a<1$), and an ergodic-to-localized edge for the short-range hopping case ($a>1$). Meanwhile, the existence of these two types of edges is found to be robust against the non-Hermitian effect. By employing the Simon-Spence theory, we analyzed the absence of the localized states for $a<1$. For the short-range hopping case, with the Avila's global theory and the Sarnak method, we consider a specific example with $a=2$ to reveal the presence of the intermediate phase and to analytically locate the intermediate regime and the ergodic-to-multifractal edge, which are self-consistent with the numerically results.Comment: 8 pages, 8 figure

From topological phase to Anderson localization in a two-dimensional quasiperiodic system

In this paper, the influence of the quasidisorder on a two-dimensional system is studied. We find that there exists a topological phase transition accompanied by a transverse Anderson localization. The topological properties are characterized by the band gap, the edge-state spectra, the transport conductance, and the Chern number. The localization transition is clearly demonstrated by the investigations of the partial inverse participation ratio, the average of level spacing ratio, and the fraction dimension. The results reveal the topological nature of the bulk delocalized states. Our work facilitates the understanding on the relationship between the topology and the Anderson localization in two-dimensional disordered systems.Comment: 6 pages, 6 figure

Quantum criticality driven by the cavity coupling in Rabi-dimer model

The superradiant phase transition (SPT) controlled by the interacting strength between the two-level atom and the photons has been a hot topic in the Rabi model and the Rabi-dimer model. The latter describes two Rabi cavities coupled with an inter-cavity hopping parameter. Moreover, the SPT in the Rabi-dimer model is found to be the same universal class that in the Rabi model by investigating the correlation-length critical exponent. In this paper, we are concerned about whether the inter-cavity hopping parameter between two Rabi cavities (i.e., the Rabi-dimer model) will induce the SPT and to which the universal class of the phase transition belongs. We analytically derive the phase boundary of the SPT and investigate the ground-state properties of the system. We uncover that the inter-cavity induced SPT can be apparently understood from the ground-state energy and the ground-state photon population, as well as the ground-state expectation value of the squared anti-symmetric mode. From the scaling analysis of the fidelity susceptibility, we numerically verify that the SPT driven by the cavity coupling belongs to the same universal class as the one driven by the atom-cavity interaction. Our work enriches the studies on the SPT and its critical behaviors in the Rabi-dimer model.Comment: 11 pages, 6 figure

Honokiol suppresses metastasis of renal cell carcinoma by targeting KISS1/KISS1R signaling

Renal cell carcinoma (RCC) is a common urological cancer worldwide and is known to have a high risk of metastasis, which is considered responsible for more than 90% of cancer associated deaths. Honokiol is a small-molecule biphenol isolated from Magnolia spp. bark and has been shown to be a potential anticancer agent involved in multiple facets of signal transduction. In this study, we demonstrated that honokiol inhibited the invasion and colony formation of highly metastatic RCC cell line 786-0 in a dose-dependent manner. DNA-microarray data showed the significant upregulation of metastasis-suppressor gene KISS1 and its receptor, KISS1R. The upregulation was confirmed by qRT-PCR analysis. Overexpression of KISS1 and KISS1R was detected by western blotting at the translation level as well. Of note, the decreased invasive and colonized capacities were reversed by KISS1 knockdown. Taken together, the results first indicate that activation of KISS1/KISS1R signaling by honokiol suppresses multistep process of metastasis, including invasion and colony formation, in RCC cells 786-0. Honokiol may be considered as a natural agent against RCC metastasis