2D Materials: from fundamentals to spintronics

Our event 2D Materials: from fundamentals to spintronics begins today at the International Institute of Physics of the Federal University of Rio Grande do Norte.

This three-week event  began with a proposal submitted almost two years ago to the International Advisory Committee of the IIP. This combined school and workshop will bring together scientists specialized in theoretical, experimental and computational tools, to present the latest advances in methodology and techniques applied to the study of 2D materials. All aspects of 2D materials from fundamental properties to applications will be discussed, including recent advances on synthesis, characterization, modeling, and devices. Furthermore, particular attention will be given to spin-related phenomena in 2D materials, focusing on the emerging area of 2D spintronics.

We hope that lecturers and participants will enjoy the event we put together and that fruitful collaborations will follow for all involved.


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X Brazilian Meeting on Simulational Physics

This week we are in Minas Gerais for the tenth edition of the Brazilian Meeting on Simulational Physics. In this tenth edition the event returns to Minas Gerais and will be held in Belo Horizonte (opening) and Ouro Preto as a Satellite Meeting of the 27th International Conference on Statistical Physics (StatPhys 27), which took place in Buenos Aires, Argentina, from July 8th through 12th, 2019.

The X BMSP will gather scientists specialized in simulation in the most diverse areas of physics, chemistry, biology and materials science, to present the latest advances in methodology and techniques applied to the study of problems through computer simulations. The event will also promote interaction among scientists working in this area, with the goal of advancing the methods and techniques available today.

The BMSP has now become a traditional event in the Brazilian physics community. Although there is “Brazilian” in the title, this year we welcome more than 40 participants from a dozen different countries.

We hope that everybody enjoys the meeting as much as we enjoyed organizing it.

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Conference on Nanophononics, Bridging Statistical Physics, Molecular Modeling and Experiments

This week we are at The Abdus Salam International Centre for Theoretical Physics to deliver an invited talk at the Conference on Nanophononics, Bridging Statistical Physics, Molecular Modeling and Experiments. My talk “Phonon transport in graphene-BN superlattices: Coherence and localization” will focus on the work done in collaboration with Isaac M. Felix since during his Master’s and Ph.D. studies.

This is my first time in Trieste and at the ICTP. Hopefully I will have other opportunities to come back to this remarkable place in the future.

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TNG @ Autumn Meeting 2019 of the Brazilian Physical Society

The Autumn Meeting of the Brazilian Physical Society (previously the Brazilian Condensed Matter Physics Meeting) is the largest Physics meeting in Brazil, gathering  nearly 1,000 researchers from Brazil and abroad. In 2019, the event takes place in Aracaju, Sergipe, from 26 to 31 of May.

The Transport in Nanostructures Group will be represented by doctoral student Isaac M. Felix, presenting some of our latest results on thermal transport and physical properties of novel 2D materials.

27/05/2018 – Posters (17:00-18:00)
Thermoelectric Properties of Bismuth-Antimony-Tellurium Selenium Alloy Nanofilms Produced by DC Sputtering and a Proposed Model
A.A. Marinho, F.A. Brito, N.P. Costa, L.F.C. Pereira and C. Chesman

28/05/2019 – Posters (17:00-18:00)
I.M. Félix and L.F.C. Pereira

29/05/2019 – Posters (17:00-18:00)
R.M. Tromer, A. Freitas, I.M. Félix, L.D. Machado, C.G. Bezerra, S.A.F. Azevedo and L.F.C. Pereira


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Scientific Reports Top 100 in Physics 2018

Scientific Reports, an online, multidisciplinary, open access journal from the publishers of Nature (Springer Nature Publishing) has released a list of their most highly accessed physics articles in 2018 (#SREPTop100). The list is based on nature.com web analytics, covering accesses from January to December 2018. According the Scientific Reports, the list features authors from around the World, and the papers highlight valuable research within physics from an international community.

Our paper “Thermal conductivity of graphene-hBN superlattice ribbons” is one of the Top 25 most accessed papers. Being more precise, it received 1836 article views in 2018, making  it the 11th most accessed paper out of more than 1133 papers published by Scientific Reports in 2018 including all areas of physics.

We are particularly proud of this work for two main reasons. First, because it is a product of Isaac M. Felix Master’s thesis, my first graduate student supervision ever. Second, because it has been completely developed and executed at UFRN, including the computational support provided by our supercomputing center NPAD. Isaac is currently on the final year of his Doctoral studies.

Coverage by UFRN news and Blog do BG.

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New paper in Carbon – Mechanical, optical and thermal transport properties of graphene-like BC3 and BC6N

Our third publication of 2019 “Outstanding strength, optical characteristics and thermal conductivity of graphene-like BC3 and BC6N semiconductors” has just been accepted for publication in Carbon.

Carbon-based 2D materials with honeycomb lattices, such as graphene, polyaniline carbon-nitride, and boron-carbide exhibit exceptional physical properties. Here, we propose two novel graphene-like materials with BC6N stoichiometry. We employ first-principles calculations to explore mechanical, optical and thermal transport characteristics of graphene-like BC3 and BC6N monolayers. The absence of imaginary phonon frequencies confirm the dynamical stability of BC3 and BC6N monolayers. First principles results also reveal that BC3 and BC6N present high elastic moduli and tensile strengths. Electronic structure calculations show that BC3 and BC6N monolayers are indirect and direct bandgap semiconductors, respectively. An analysis of their optical absorption spectra reveals absorption peaks for in-plane polarization in the visible range. Finally, ab-initio based anharmonic lattice dynamics calculations predict room temperature lattice thermal conductivities of 410 and 1710  W/-K, respectively. Notably, the thermal conductivity of BC6N is one of the highest among 2D materials. Our results indicate that those new BC6N monolayers are promising candidates for the design of novel nanodevices.

This work is our most recent collaboration with Dr. Bohayra Mortazavi and Prof. Timon Rabczuk at Bauhaus-Universität Weimar.

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Physics education paper accepted in Revista Brasileira de Ensino de Física

My first ever publication in a physics education journal, “Total entropy variation for an object in contact with heat reservoirs: the path to reversibility” has just been accepted for publication in Revista Brasileira de Ensino de Física, published by the Brazilian Physical Society.

In this paper we explore the second law of thermodynamics, which is one of the least understood fundamental physical laws among science and engineering students, possibly due to its subtleness and alternative statements. We consider the entropy variation of an isolated system composed of an object and one or more heat reservoirs, as the absolute temperature of the object varies due to heat exchange with the reservoirs, one at a time. We obtain a general expression for the total entropy variation, ∆S, in terms of the object’s heat capacity and the number of reservoirs, N. We employ a simple numerical routine to show that ∆S decreases as N increases, approaching zero as N becomes very large. Since the temperature difference between subsequent reservoirs becomes infinitesimal as N increases, we analytically show that ∆S vanishes, in accordance with the second law of thermodynamics. In the manuscript we also propose an undergraduate exam problem based on this demonstration.

The idea for this work came to me when I was preparing a problem set for the undergraduate Statistical Physics course, which I taught at UFRN in 2017 and 2018. The course was based on “Fundamentals of Statistical and Thermal Physics” by F. Reif, which contains a similar problem in its Chapter 4. The analytical solution was presented by one of the students in the class, Lucas R.D. Freitas, who co-authored the manuscript with me.

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Colloquium at UNICAMP

This week I am presenting a Colloquium at the Institute of Physics (IFGW) at UNICAMP, the top ranking research university in Latin America. It is a great honour for me and I thank my host, Prof. Alexandre F. Fonseca, for this kind invitation. During the week I will also discuss new projects with Alexandre and his group.

The presentation is entitled “Exploring phonon thermal transport in 2D materials with molecular dynamics simulations”. Since its aimed at a broad audience of graduate students and faculty, it begins with a general introduction to nanotechnology, moving on to the relationship between thermal transport and dimensionality, molecular dynamics simulations and finally to our results. I will detail our quest to improve thermal conductivity calculations for graphene from 2013 to 2017, and conclude with some recent results by Ph.D. student Isaac Felix.

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Paper accepted in Physical Review E – Dirac wave transmission in Lévy disordered systems

Our first paper of 2019 “Dirac wave transmission in Lévy disordered systems” has just been accepted for publication in Physical Review E, an American Physical Society journal.

In this paper we investigate the propagation of electronic waves described by the Dirac equation subject to a certain disorder distribution. The disorder takes the form of potential barriers following an unusual statistical distribution, know as the Lévy distribution. Our numerical calculations reveal a phase transition from anomalous to standard to anomalous localization as the incidence energy increases. In contrast, electronic waves described by the Schrödinger equation do not present such transition. We obtain the phase diagram delimiting anomalous and standard localization regimes, and argue that these transitions can also be characterized by the dispersion of the transmission. We attribute the transition to an abrupt reduction in transmittance when the incidence angle is higher than a critical value, which induces a decrease in transmission fluctuations.

This work is a collaboration with Jonas R. F. Lima and Anderson L. R. Barbosa, both at Universidade Federal Rural de Pernambuco. A.L.R. Barbosa was also my graduate school colleague at UFPE back in 2003-2005. Networking does pay off.

Posted in TNG Publications

Brazilian Academy of Sciences

We just got news I have been elected Affiliated Member of the Brazilian Academy of Sciences (ABC). This is a 5-year membership for Brazilian scientists under 40 years of age, recognizing young researchers of notable talent. My term in the ABC will be from Jan. 01, 2019 to Dec. 31, 2023. This is certainly a great honor, for which I am very grateful.

My profile can be found here.

The Brazilian Academy of Sciences was founded in 1916. It is a non profit, non governmental, independent honorific scientific society. It acts as consultant for the federal government performing technical studies and studies on scientific policies. It focuses in the scientific development of the Country, the interaction among Brazilian scientists and their interaction with researchers from other nations.

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