114 research outputs found
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 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 to . 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 () and quasiperiodic parameter is studied, where
is the power-law index, is the hopping distance, and is a member of
the metallic mean family. We find that under the weak non-Hermitian effect,
there preserves regimes where the fraction of ergodic
eigenstates is -dependent as L ( is the system size)
similar to those in the Hermitian case. However, 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 in the single-particle spectrum, i.e., an ergodic-to-multifractal
edge for the long-range hopping case (), and an ergodic-to-localized edge
for the short-range hopping case (). 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 . For the short-range hopping case, with the Avila's global
theory and the Sarnak method, we consider a specific example with 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
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