RepositóriUM Collection: Artigos/Papers (with refereeing)Artigos/Papers (with refereeing)http://hdl.handle.net/1822/19172019-11-17T01:14:36Z2019-11-17T01:14:36ZFaraday effect in graphene enclosed in an optical cavity and the equation of motion method for the study of magneto-optical transport in solidsFerreira, Aires Francisco Lemos GonçalvesViana-Gomes, J.Bludov, Yuliy V.Pereira, V.Peres, N. M. R.Castro Neto, A. H.http://hdl.handle.net/1822/618402019-10-23T15:43:08Z2019-10-23T13:27:59Z<b>Title</b>: Faraday effect in graphene enclosed in an optical cavity and the equation of motion method for the study of magneto-optical transport in solids
<b>Author(s)</b>: Ferreira, Aires Francisco Lemos Gonçalves; Viana-Gomes, 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 magneto-optical properties of metals and semiconductors. It is shown that properly regularized EOM solutions are fully equivalent to the Kubo formula.
<b>Type</b>: article2019-10-23T13:27:59ZSolution of the quantum harmonic oscillator plus a delta-function potential at the origin: The oddness of its even-parity solutionsViana-Gomes, J.Peres, N. M. R.http://hdl.handle.net/1822/618392019-10-23T13:59:06Z2019-10-23T13:16:07Z<b>Title</b>: Solution of the quantum harmonic oscillator plus a delta-function potential at the origin: The oddness of its even-parity solutions
<b>Author(s)</b>: Viana-Gomes, J.; Peres, N. M. R.
<b>Abstract(s)</b>: We derive the energy levels associated with the even-parity wavefunctions of the harmonic oscillator with an additional delta-function potential at the origin. Our results bring to the attention of students a non-trivial 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>: article2019-10-23T13:16:07ZTwisted bilayer graphene: low-energy physics, electronic and optical propertiesCatarina, G.Amorim, B.Castro, Eduardo V.Lopes, J. M. Viana ParentePeres, N. M. R.http://hdl.handle.net/1822/615652019-10-09T11:42:18Z2019-10-02T08:31:33Z<b>Title</b>: Twisted bilayer graphene: low-energy 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
two-dimensional (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 low-energy van Hove singularities.
The optical response of this system is then addressed by computing the optical
conductivity and the dispersion relation of tBLG surface plasmon-polaritons.
<b>Type</b>: article2019-10-02T08:31:33ZHybrid plasmon-magnon polaritons in graphene-antiferromagnet heterostructuresBludov, Yuliy V.Gomes, J. N.Farias, G. A.Fernández-Rossier, J.Vasilevskiy, MikhailPeres, N. M. R.http://hdl.handle.net/1822/614942019-10-19T11:46:17Z2019-09-25T08:47:00Z<b>Title</b>: Hybrid plasmon-magnon polaritons in graphene-antiferromagnet heterostructures
<b>Author(s)</b>: Bludov, Yuliy V.; Gomes, J. N.; Farias, G. A.; Fernández-Rossier, J.; Vasilevskiy, Mikhail; Peres, N. M. R.
<b>Abstract(s)</b>: We consider a hybrid structure formed by graphene and an insulating
antiferromagnet, separated by a dielectric of thickness up to $d\simeq 500
\,nm$. When uncoupled, both graphene and the antiferromagnetic surface host
their own polariton modes coupling the electromagnetic field with plasmons in
the case of graphene, and with magnons in the case of the antiferromagnet. We
show that the hybrid structure can host two new types of hybrid polariton
modes. First, a surface magnon-plasmon polariton whose dispersion is radically
changed by the carrier density of the graphene layer, including a change of
sign in the group velocity. Second, a surface plasmon-magnon polariton formed
as a linear superposition of graphene surface plasmon and the antiferromagnetic
bare magnon. This polariton has a dispersion with two branches, formed by the
anticrossing between the dispersive surface plasmon and the magnon. We discuss
the potential these new modes have for combining photons, magnons, and plasmons
to reach new functionalities.
<b>Type</b>: article2019-09-25T08:47:00ZExcitonic magneto-optics in monolayer transition metal dichalcogenides: From nanoribbons to two-dimensional responseHave, J.Peres, N. M. R.Pedersen, T. G.http://hdl.handle.net/1822/614932019-10-19T11:51:27Z2019-09-25T08:29:25Z<b>Title</b>: Excitonic magneto-optics in monolayer transition metal dichalcogenides: From nanoribbons to two-dimensional response
<b>Author(s)</b>: Have, J.; Peres, N. M. R.; Pedersen, T. G.
<b>Abstract(s)</b>: The magneto-optical response of monolayer transition metal dichalcogenides
(TMDs), including excitonic effects, is studied using a nanoribbon geometry. We
compute the diagonal optical conductivity and the Hall conductivity. Comparing
the excitonic optical Hall conductivity to results obtained in the independent
particle approximation, we find an increase in the amplitude corresponding to
one order of magnitude when excitonic effects are included. The Hall
conductivities are used to calculate Faraday rotation spectra for MoS2 and
WSe2. Finally, we have also calculated the diamagnetic shift of the exciton
states of WSe2 in different dielectric environments. Comparing the calculated
diamagnetic shift to recent experimental measurements, we find a very good
agreement between the two.
<b>Type</b>: article2019-09-25T08:29:25Z