Zero-energy states in graphene quantum dot with wedge disclination

We investigate the effects of wedge disclination on charge carriers in circular graphene quantum dots subjected to a magnetic flux. Using the asymptotic solutions of the energy spectrum for large arguments, we approximate the scattering matrix elements, and then study the density of states. It is found that the density of states shows several resonance peaks under various conditions. In particular, it is shown that the wedge disclination is able to change the amplitude, width, and positions of resonance peaks.Comment: 10 pages, 10 figure

Energy levels of gapped graphene quantum dots in external fields

We investigate the energy levels of fermions within a circular graphene quantum dot (GQD) subjected to external magnetic and Aharonov-Bohm fields. Solving the eigenvalue equation for two distinct regions allows us to determine the eigenspinors for the valleys $K$ and $K^\prime$. By establishing the continuity of eigenspinors at the GQD interface, we derive an equation that reveals the reliance of energy levels on external physical parameters. Our observations suggest that the symmetry of energy levels hinges on the selected physical parameters. We observe that at low magnetic fields, the energy levels display degeneracy, which diminishes as the field strength increases, coinciding with the convergence of energy levels toward the Landau levels. We illustrate that the introduction of a magnetic flux into the GQD leads to the creation of an energy gap, extending the trapping time of electrons without perturbing the system. Conversely, the addition of gap energy widens the band gap, disrupting the system's symmetry by introducing new energy levels.Comment: 9 pages, 7 figure

Electron trapping in graphene quantum dots with magnetic flux

It is known that the appearance of Klein tunneling in graphene makes it hard to keep or localize electrons in a graphene-based quantum dot (GQD). However, a magnetic field can be used to temporarily confine an electron that is traveling into a GQD. The electronic states investigated here are resonances with a finite trapping time, also referred to as quasi-bound states. By subjecting the GDQ to a magnetic flux, we study the scattering phenomenon and the Aharonov-Bohm effect on the lifetime of quasi-bound states existing in a GQD. We demonstrate that the trapping time increases with the magnetic flux sustaining the trapped states for a long time even after the flux is turned off. Furthermore, we discover that the probability density within the GQD is also clearly improved. We demonstrate that the trapping time of an electron inside a GQD can be successfully extended by adjusting the magnetic flux parameters.Comment: 10 pages, 7 figure

Tunneling phase diagrams in anisotropic Multi-Weyl semimetals

Motivated by the exciting prediction of Multi-Weyl topological semimetals that are stabilized by point group symmetries [Phys. Rev. Lett. 108 (2012) 266802], we study tunneling phenomena for a class of anisotropic Multi-Weyl semimetals. We find that a distant detector for different ranges of an anisotropy parameter $\lambda$ and incident angle $\theta$ will measure a different number of propagating transmitted modes. We present these findings in terms of phase diagrams that is valid for an incoming wave with fixed wavenumber $k$--energy is not fixed. To gain a deeper understanding of this phenomenon we then focus on the simplest case of an anisotropic quadratic Weyl-semimetal and analyze tunneling coefficients analytically and numerically to confirm the observations from the phase diagram. Our results show non-analytical behavior, which is the hallmark of a phase transition. This serves as a motivation to make a formal analogy with phase transitions that are known from statistical mechanics. Specifically, we argue that the long distance limit in our tunneling problem takes the place of the thermodynamic limit in statistical mechanics. More precisely, find a direct formal connection to the recently developed formalism for dynamical phase transitions [Reports on Progress in Physics 81 (5) (2018) 054001]. We propose that this analogy to phase transitions can help classify transport properties in exotic semimetals

Viroid infection and rootstocks affect productivity and fruit quality of the Tunisian citrus cultivar Maltaise demi sanguine

In Tunisia, sweet orange citrus cultivars are usually grafted on sour orange rootstock. However, this rootstock is susceptible to Citrus tristeza virus (CTV). A trial was established in 2005 to evaluate the performance of newly introduced rootstocks compared to sour orange, using the sweet orange cultivar ‘Maltaise demi sanguine’ as the grafted scion. The effect of single or mixed viroid infections were monitored over 12 years. Once established, tree growth, cumulative yield, tree performance and fruit quality of ‘Maltaise sweet orange’ were assessed from 2008. Mixed viroid infections caused significant decreases (39 to 60%) in the canopy volume of ‘Maltaise’ grafted on Carrizo citrange, Swingle citrumelo, Cleopatra mandarin, Rangpur lime, Volkamer lemon and Trifoliate orange. The cumulative yield of trees grafted on’Alemow’ (Citrus macrophylla) and inoculated with Hop stunt viroid (HSVd) was 76% less than the healthy control. Mixed infections caused production decreases of 56% from trees grafted on Swingle citrumelo and 69% from those grafeted on Trifoliate orange. When quality parameters of fruit from trees infected with each viroid, and combinations of viroids were compared, no significant differences were recorded.

Viroid infection and rootstocks affect productivity and fruit quality of the Tunisian citrus cultivar Maltaise demi sanguine

In Tunisia, sweet orange citrus cultivars are usually grafted on sour orange rootstock. However, this rootstock is susceptible to Citrus tristeza virus (CTV). A trial was established in 2005 to evaluate the performance of newly introduced rootstocks compared to sour orange, using the sweet orange cultivar ‘Maltaise demi sanguine’ as the grafted scion. The effect of single or mixed viroid infections were monitored over 12 years. Once established, tree growth, cumulative yield, tree performance and fruit quality of ‘Maltaise sweet orange’ were assessed from 2008. Mixed viroid infections caused significant decreases (39 to 60%) in the canopy volume of ‘Maltaise’ grafted on Carrizo citrange, Swingle citrumelo, Cleopatra mandarin, Rangpur lime, Volkamer lemon and Trifoliate orange. The cumulative yield of trees grafted on’Alemow’ (Citrus macrophylla) and inoculated with Hop stunt viroid (HSVd) was 76% less than the healthy control. Mixed infections caused production decreases of 56% from trees grafted on Swingle citrumelo and 69% from those grafeted on Trifoliate orange. When quality parameters of fruit from trees infected with each viroid, and combinations of viroids were compared, no significant differences were recorded.