Sample dispersion in isotachophoresis with Poiseuille counterflow

A particular mode of isotachophoresis (ITP) employs a pressure-driven flow opposite to the sample electromigration direction in order to anchor a sample zone at a specific position along a channel or capillary. We investigate this situation using a two-dimensional finite-volume model based on the Nernst-Planck equation. The imposed Poiseuille flow profile leads to a significant dispersion of the sample zone. This effect is detrimental for the resolution in analytical applications of ITP. We investigate the impact of convective dispersion, characterized by the area-averaged width of a sample zone, for various values of the sample P\'{e}clet-number, as well as the relative mobilities of the sample and the adjacent electrolytes. A one-dimensional model for the area-averaged concentrations based on a Taylor-Aris-type effective axial diffusivity is shown to yield good agreement with the finite-volume calculations. This justifies the use of such simple models and opens the door for the rapid simulation of ITP protocols with Poiseuille counterflow

Tuning the electrical transport properties of double-walled carbon nanotubes by semiconductor and semi-metal filling

Manipulating the electrical properties of carbon nanotubes through semi-metal or semiconductor filling is of paramount importance in the realization of nano-electronic devices based on one dimensional composite materials. From low temperature electrical conductivity measurements of a network, of empty and filled double-walled carbon nanotubes (DWNT’s), we report a transition in electrical transport features from hopping to weakly activated conduction by HgTe filling and also semi-metallic conduction in selenium (Se) filled DWNT’s. Magneto-resistance (MR) studies of the filled DWNT’s show suppression of the hopping conduction and a signature of 3D weak localization for Se@DWNT’s at low temperatures and high magnetic fields. These results are discussed on the basis of strength of interaction between the filler material and the inner-walls of the host DWNT’s, which enhances the electronic density of states (DOS) in the material as well as the change in the property of the filler material due to constrained encapsulation

Conductivity crossover in nano-crystalline diamond films: Realization of a disordered superlattice-like structure

We present the electrical transport characteristics of a batch of nano-crystalline diamond films of varying nitrogen concentrations and explain the conduction mechanism by the disordered quasi-superlattice model applied to semiconductor heterostructures. Synthesized by the hot filament chemical vapour deposition technique, the degree of structural disorder in the films, confirmed from Raman spectroscopy, is found to be controllable, resulting in the transition of conduction mechanism from localized and activated to the metallic conduction regime. Hence through high field magneto-resistance measurements at low temperatures we firmly establish a conductivity crossover from hopping to 3D weak localization. The long electronic dephasing time and its weak temperature dependence suggest the possibility for diamond-based high-speed device applications

Realizing highly entangled states in asymmetrically coupled three NV centers at room temperature

Despite numerous efforts the coupling between randomly arranged multi-NV centers and also resonators has not been improved significantly mainly due to our limited knowledge of their entanglement times (2t_ent). Here, we demonstrate a very strong coupling between three-NV centers by using a simulated triple electron-electron resonance experiment based on a new quantum (U_C) gate on IBM quantum simulator with 2t_ent ~12.5 microsecond arranged is a triangular configuration. Interestingly through breaking the symmetry of couplings an even lower 2t_ent ~6.3 {\mu}s can be achieved. This simulation not only explains the luminescence spectra in recently observed three-NV centers [Haruyama, Nat. Commun. 2019] but also shows a large improvement of the entanglement in artificially created structures through a cyclic redistribution of couplings. Realistically disordered coupling configurations of NV centers qubits with short time periods and high (0.89-0.99) fidelity of states clearly demonstrate possibility of accurate quantum registers operated at room temperature