arXiv subjects

A. C. A. Ramos

Publications and source records attributed to A. C. A. Ramos.

9 recordsLinked to original sources

arXiv2024

Encoding quantum bits in bound electronic states of a graphene nanotorus

We propose to use the quantum states of an electron trapped on the inner surface of a graphene nanotorus to realize as a new kind of physical quantum bit, which can be used to encode quantum information. Fundamental tasks for quantum information processing, such as the qubit initialization and the implementation of arbitrary single qubit gates, can then be performed using external magnetic and electric fields. We also analyze the robustness of the device again systematic errors, which can be suppressed by a suitable choice of the external control fields. These findings open new prospects for the development an alternative platform for quantum computing, the scalability of which remains to be determined.

quant-ph↗

arXiv2024

Electronic states in a bilayer graphene quantum ripple

In this paper, we investigate the influence of the geometry in the electronic states of a quantum ripple surface. We have considered an electron governed by the spinless stationary Schrödinger equation constrained to move on the ripple surface due to a confining potential from which the Da Costa potential emerges. We investigate the role played by the geometry and orbital angular momentum on the electronic states of the system.

cond-mat.mes-hall↗

arXiv2022

Generalized Ellis-Bronnikov graphene wormhole

In this paper, we investigate the spinless stationary Schrödinger equation for the electron when it is permanently bound to a generalized Ellis-Bronnikov graphene wormhole-like surface. The curvature gives rise to a geometric potential affecting thus the electronic dynamics. The geometry of the wormhole's shape is controlled by the parameter $n$ which assumes even values. We discuss the role played by the parameter $n$ and the orbital angular momentum on bound states and probability density for the electron.

gr-qc↗

arXiv2021

Bose-Einstein condensation in Hořava-Lifshitz theory

In this paper we study the corrections emergent from a Hořava-Lifshitz extension of the complex scalar sector to the Bose-Einstein condensation and to the thermodynamics parameters. We initially discussed some features of the model to only then compute the corrections to the Bose-Einstein condensation. The calculations were done by computing the generating functional, from which we extract the thermodynamics parameters. We also obtained the Lifshitz scaling correction for the critical temperature $T_c$ that sets the Bose-Einstein Condensation.

hep-th↗

arXiv2021

Position-dependent mass effects on a bilayer graphene catenoid bridge

We study the electronic properties of a position-dependent effective mass electron on a bilayer graphene catenoid bridge. We propose a position-dependent mass (PDM) as a function of both gaussian and mean curvature. The hamiltonian exhibits parity and time-reversal steaming from the bridge symmetry. The effective potential contains the da Costa, centrifugal and PDM terms which are concentrated around the catenoid bridge. For zero angular momentum states, the PDM term provides a transition between a reflectionless to a double-well potential. As a result, the bound states undergo a transition from a single state around the bridge throat into two states each one located at rings around the bridge. Above some critical value of the PDM coupling constant, the degeneracy is restored due to double-well tunneling resonance.

cond-mat.mes-hall↗

arXiv2020

Effects of Lorentz violation in the Bose-Einstein condensation

In this paper we study the corrections emergent from a Lorentz-violating CPT-odd extension of the complex scalar sector to the Bose-Einstein condensation and to the thermodynamics parameters. We initially discussed some features of the model to only then compute the corrections to the Bose-Einstein condensation. The calculations were done by computing the generating functional, from which we extract the thermodynamics parameters. We also obtained a Lorentz-violating correction for the critical temperature $T_c$ that sets the Bose-Einstein Condensation.

hep-th↗

arXiv2020

Electronic properties of a nanotorus

In this paper we study the properties of an electron trapped on a torus surface. We consider the influence of surface curvature on the spectrum and the behaviour of the wave function. In addition, the effects of external electric and magnetic fields were explored. Two toroid configurations were considered, namely, a torus-like configuration and a ring-like configuration both in agreement with experimental data. We also obtain the bound states and discuss the role of geometry on the Landau levels.

cond-mat.mes-hall↗

arXiv2012

Edge magnetoplasmons in a wide armchair graphene ribbon with a weak superlattice potential: finite frequency gaps and zero group velocity

We show strong effects of a weak and smooth, on the magnetic length, superlattice potential upon edge magnetoplasmons (EMPs) at the armchair edge, with a smooth steplike electrostatic lateral confining potential, of a wide graphene channel in the $ν=2$ quantum Hall effect regime. The superlattice potential leads to essential enlargement of a number of EMPs, descend from two fundamental EMPs in the absence of superlattice. For the wave vector $k_{x}$ within the first Brillouin zone, the EMPs show as the regions of acoustical or quasi-acoustical dispersion, with a finite value of group velocity, so the regions with frequency gaps, where a group velocity is nullified at some $k_{x}$. We obtain that for $k_{x} \to 0$ only for two EMPs the frequency tends to zero as for other EMPs it obtains finite values. Strong dependence of dispersion relations of the EMPs from the period of the superlattice $a_{0}$ and the distance $d$ from a metallic gate is shown; in particular, for typical size of a gap, for characteristic value of the frequency and $k_{x}$ at which the group velocity is reduced to zero. At the frequency that corresponds to zero group velocity of pertinent fundamental EMP branch the response of the system should present a strong resonance.

cond-mat.mes-hall↗

arXiv2007

Transport properties of a 2DEG in the presence of a tilted magnetic field

The effect of a tilted dc magnetic field on the transport properties of a two dimensional electron gas (2DEG) is studied. The influence of the component of magnetic field parallel to the surface is analyzed and the dependence of the Fermi energy on the intensity and direction of the external field is discussed. Numerical results are obtained for the Hall conductivity considering values of electronic densities and strength of the dc magnetic field that are currently obtained in many laboratories

cond-mat.mes-hall↗