RepositóriUM Collection: Artigos/Papers (with refereeing)
http://hdl.handle.net/1822/1917
Artigos/Papers (with refereeing)
Mon, 19 Oct 2020 22:19:45 GMT
20201019T22:19:45Z

Finiteenergy Landau liquid theory for the onedimensional Hubbard model: Pseudoparticle energy bands and degree of localization/delocalization
http://hdl.handle.net/1822/63468
<b>Title</b>: Finiteenergy Landau liquid theory for the onedimensional Hubbard model: Pseudoparticle energy bands and degree of localization/delocalization
<b>Author(s)</b>: Carmelo, JosÃ© Manuel Pereira; Sacramento, P. D.
<b>Abstract(s)</b>: In this paper we consider the onedimensional Hubbard model and study the deviations from the groundstate values of double occupation which result from creation or annihilation of holons, spinons, and pseudoparticles. These quantum objects are such that all energy eigenstates are described by their occupancy configurations. The bandmomentum dependence of the obtained doubleoccupation spectra provides important information on the degree of localization/delocalization of the realspace lattice electron site distribution configurations associated with the pseudoparticles. We also study the band momentum, onsite electronic repulsion, and electronic density dependence of the pseudoparticle energy bands. The shape of these bands plays an important role in the finiteenergy spectral properties of the model. Such a shape defines the form of the lines in the momentumenergy/frequency plane where the peaks and edges of the oneelectron and twoelectron spectral weight of physical operators are located. Our findings are useful for the study of the oneelectron and twoelectron spectralweight distribution of physical operators.
<b>Type</b>: article
Wed, 29 Jan 2020 12:05:40 GMT
http://hdl.handle.net/1822/63468
20200129T12:05:40Z

Surface plasmonpolaritons in graphene, embedded into medium with gain and losses
http://hdl.handle.net/1822/63097
<b>Title</b>: Surface plasmonpolaritons in graphene, embedded into medium with gain and losses
<b>Author(s)</b>: Zhernovnykova, O. A.; Popova, O. V.; Deynychenko, G. V.; Deynichenko, T. I.; Bludov, Yuliy V.
<b>Abstract(s)</b>: The paper deals with the theoretical consideration of surface plasmonpolaritons in the graphene monolayer, embedded into dielectric with spatially separated gain and losses. It is demonstrated, that presence of gain and losses in the system leads to the formation of additional mode of graphene surface plasmonpolaritons, which does not have its counterpart in the conservative system. When the gain and losses are mutually balanced, the position of exceptional pointtransition point between unbroken and broken [Formula: see text]symmetrycan be effectively tuned by graphene's doping. In the case of unbalanced gain and losses the spectrum of surface plasmonpolaritons contains spectral singularity, whose frequency is also adjustable through the electrostatic gating of graphene.
<b>Type</b>: article
Thu, 09 Jan 2020 10:35:46 GMT
http://hdl.handle.net/1822/63097
20200109T10:35:46Z

Faraday effect in graphene enclosed in an optical cavity and the equation of motion method for the study of magnetooptical transport in solids
http://hdl.handle.net/1822/61840
<b>Title</b>: Faraday effect in graphene enclosed in an optical cavity and the equation of motion method for the study of magnetooptical transport in solids
<b>Author(s)</b>: Ferreira, Aires Francisco Lemos GonÃ§alves; VianaGomes, J.; Bludov, Yuliy V.; Pereira, V.; Peres, N. M. R.; Castro Neto, A. H.
<b>Abstract(s)</b>: We show that by enclosing graphene in an optical cavity, giant Faraday rotations in the infrared regime are generated and measurable Faraday rotation angles in the visible range become possible. Explicit expressions for the Hall steps of the Faraday rotation angle are given for relevant regimes. In the context of this problem we develop an equation of motion (EOM) method for calculation of the magnetooptical properties of metals and semiconductors. It is shown that properly regularized EOM solutions are fully equivalent to the Kubo formula.
<b>Type</b>: article
Wed, 23 Oct 2019 13:27:59 GMT
http://hdl.handle.net/1822/61840
20191023T13:27:59Z

Solution of the quantum harmonic oscillator plus a deltafunction potential at the origin: The oddness of its evenparity solutions
http://hdl.handle.net/1822/61839
<b>Title</b>: Solution of the quantum harmonic oscillator plus a deltafunction potential at the origin: The oddness of its evenparity solutions
<b>Author(s)</b>: VianaGomes, J.; Peres, N. M. R.
<b>Abstract(s)</b>: We derive the energy levels associated with the evenparity wavefunctions of the harmonic oscillator with an additional deltafunction potential at the origin. Our results bring to the attention of students a nontrivial and analytical example of a modification of the usual harmonic oscillator potential, with emphasis on the modification of the boundary conditions at the origin. This problem calls the attention of the students to an inaccurate statement in quantum mechanics textbooks often found in the context of the solution of the harmonic oscillator problem.
<b>Type</b>: article
Wed, 23 Oct 2019 13:16:07 GMT
http://hdl.handle.net/1822/61839
20191023T13:16:07Z

Twisted bilayer graphene: lowenergy physics, electronic and optical properties
http://hdl.handle.net/1822/61565
<b>Title</b>: Twisted bilayer graphene: lowenergy physics, electronic and optical properties
<b>Author(s)</b>: Catarina, G.; Amorim, B.; Castro, Eduardo V.; Lopes, J. M. Viana Parente; Peres, N. M. R.
<b>Abstract(s)</b>: Van der Waals (vdW) heterostructures formed by stacking or growing
twodimensional (2D) crystals on top of each other have emerged as a new
promising route to tailor and engineer the properties of 2D materials. Twisted
bilayer graphene (tBLG), a simple vdW structure where the interference between
two misaligned graphene lattices leads to the formation of a moir\'e pattern,
is a test bed to study the effects of the interaction and misalignment between
layers, key players for determining the electronic properties of these
stackings. In this chapter, we present in a pedagogical way the general theory
used to describe lattice mismatched and misaligned vdW structures. We apply it
to the study of tBLG in the limit of small rotations and see how the coupling
between the two layers leads both to an angle dependent renormalization of
graphene's Fermi velocity and appearance of lowenergy van Hove singularities.
The optical response of this system is then addressed by computing the optical
conductivity and the dispersion relation of tBLG surface plasmonpolaritons.
<b>Type</b>: article
Wed, 02 Oct 2019 08:31:33 GMT
http://hdl.handle.net/1822/61565
20191002T08:31:33Z