Graduate Program in Physics at UFSC, Florianópolis

 THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar: 

   O Lado Escuro do Universo  

Rogerio Rosenfeld – Instituto de Física Teórica / UNESP

Abstract:

 Sabemos hoje que apenas 5% do Universo é composto de átomos. Nesse colóquio vou descrever brevemente o que pensamos que são os 95% restantes: matéria escura e energia escura.

Date: 10/April/2015 – (friday) – Place: Sala 212 – Auditório do Departamento de Física– Time: 10h15min

THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar: 

   O Centenário da Relatividade Geral 

Prof. Dr. Victor de Oliveira Rivelles

Instituto de Física – USP

 Abstract:

 Apresentaremos um panorama geral de uma das teorias que revolucionaram a física do século XX. Veremos o que levou Einstein a formular a relatividade geral, as mudanças de paradigmas que gerou, seus efeitos mais importantes, dentre eles ondas gravitacionais e buracos negros e como levou ao nascimento de um novo ramo da ciência, a cosmologia.

Date: 13/March/2015 – (friday) – Place: Sala 212 – Auditório do Departamento de Física– Time: 10h15min

 THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar: 

   Quantum dipolar gases for quantum magnetism 

Laurent Vernac

Laboratoire de Physique des Lasers / Université Paris 13

Abstract:

Bose Einstein Condensates (BEC) have been obtained with ultra cold atoms in 1995. In these quantum gases all atoms are in the same quantum state, which gives them unique properties in terms of coherence, and allows for observation of matter interference, superfluidity, or transition from superfluid to Mott insulator states in an optical lattice. I will present experimental results obtained in our group with chromium atoms. Due to the high spin (S=3) in the ground state of chromium, there are large magnetic dipole-dipole interactions (DDIs) between the atoms, which are long range, and anisotropic. They confer specific properties to chromium BECs. For example, the excitation spectrum depends on the direction of the magnetic field: a Cr BEC can be seen as an anisotropic superfluid [1]. DDIs allow as well the change of the magnetization of the sample, which leads to spontaneous depolarization of the BEC at low magnetic fields, and multi-components BECs [2,3]. The main part of my talk will be devoted to the results we have obtained in a 3D optical lattice. We have studied spin exchange dynamics due to DDIs in the Mott insulator state, with one or two atoms per lattice site [4]. Our system is well described by an effective XXZ spin Hamiltonian, with Ising and exchange terms. We thus obtain an interesting system for quantum simulation, which realizes a spin model used in condensed matter physics, with true spin-spin interactions. As correlations build up between the few thousands of atoms loaded in the lattice, our system should reveal as well the existence of entanglement between many particles, through the finding of a relevant experimental entanglement witness. I will conclude by perspectives offered by our recent production of a chromium quantum gas with the fermionic isotope (Fermi Sea) [5].

REFS.:

[1] Anisotropic Excitation Spectrum of a Dipolar Quantum Bose Gas G. Bismut et al., Phys. Rev. Lett. 109, 155302 (2012)

[2] Spontaneous demagnetization of a dipolar spinor Bose gas atultra-low magnetic field

B. Pasquiou, Phys. Rev. Lett. 106, 255303 (2011)

[3] Thermodynamics of a Bose-Einstein condensate with free magnetization B. Pasquiou et al., Phys. Rev. Lett., 108, 045307 (2012)

[4] Nonequilibrium Quantum Magnetism in a Dipolar Lattice Gas A. de Paz et al., Phys. Rev. Lett., 111, 185305 (2013)

[5] Chromium Dipolar Fermi SeaB. Naylor et al., Phys. Rev. A 91, 011603(R) (2015)

Date: 6/March/2015 – (friday) – Place: Sala 212 – Auditório do Departamento de Física– Time: 10h15min

THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar: 

Correlating Structural, Electronic and Ionic Diffusion Properties of Nanomaterials for Energy Storage 

Profª Drª Corinne Arrouvel / UFSCar – Sorocaba

 Abstract:

 The quest of new materials at the nanoscale is an important topic in the modern society. The industrial interest is to improve the energy conversion, the storage capacity and the kinetic of the electrochemical energy in high-technology devices. Materials should be in addition low cost, stable under a wide range of temperature and pressure conditions and safe. This talk will introduce basic concepts of electrochemistry, of bulk and surface properties in order to explain the difference of energy carrier transport mechanisms in rechargeable lithium batteries, capacitors, solid oxide fuel cells and solar cells. Combining computational and experimental techniques, we show that some key aspects are based on the search of optimized size and morphology of their nanocomponents. Anisotropic energy pathways and crystal shape will be therefore highlighted.

Date: 05/December/2014 – (Friday) – Place: Sala 212 – Auditório do Departamento de Física- Time: 10h15min

THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar: 

Nonperturbative QCD effects in forward scattering at LHC 

Prof. Emerson Gustavo de Souza Luna – IF/UFRGS

Abstract:

We study infrared contributions to semihard parton-parton interactions by considering an effective charge whose finite infrared behavior is constrained by a dynamical mass scale. Using an eikonal QCD-based model in order to connect this semihard parton-level dynamics to the hadron-hadron scattering, we obtain predictions for the proton-proton ($pp$) and antiproton-proton ($\bar{p}p$) total cross sections, $\sigma_{tot}^{pp,\bar{p}p}$, as well as for the ratios of the real to imaginary part of the forward scattering amplitude, $\rho^{pp,\bar{p}p}$. We discuss the theoretical aspects of this formalism and consider the phenomenological implications of a class of energy-dependent form factors in the high-energy behavior of the forward amplitude. Our results, obtained using a group of updated sets of parton distributions, are consistent with the recent data from the TOTEM experiment.

Date: 28/November/2014 – (Friday) – Place: Sala 212 – Auditório do Departamento de Física- Time: 10h15min

 THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar: 

   Aplicações de Transistores de Filme Fino em Displays Transparentes e Flexíveis 

Prof. Dr. Lucas Fugikawa Santos

Universidade Estadual Paulista, UNESP, Departamento de Física – Campus de São José do Rio Preto.

Abstract:

Transistores de filme fino (TFTs) são dispositivos eletrônicos que têm sido amplamente aplicados em circuitos de controle de displays planos de matriz ativa baseados tanto em cristais líquidos (AMLCDs) quanto em diodos emissores de luz orgânicos (AMOLEDs). Embora a grande maioria dos displays de matriz ativos produzidos atualmente utilizem como material ativo o silício amorfo (a-Si), novos tipos de materiais têm sido estudados para poderem suprir as exigências de aplicações que irão requerer maiores taxas de repetição, recursos 3-D, grandes áreas, transparência e flexibilidade. Óxidos metálicos amorfos como o óxido de zinco (ZnO), óxido de zinco e índio (IZO) e óxido de índio, gálio e zinco (IGZO) são materiais que têm sido considerados como bons candidatos para substituir o a-Si em determinadas aplicações, em especial as que demandam transparência e flexibilidade. Recentemente, a produção de TFTs desses materiais depositados por solução tem chamado bastante a atenção, devido ao enorme potencial para a deposição em grandes áreas e a diminuição dos custos de produção. No presente trabalho, iremos apresentar os resultados de TFTs de óxidos metálicos processados por solução e discutir sobre os desafios tecnológicos que precisam ser superados para que esse tipo de tecnologia alcance o mercado.

[1] K.K. Banger, Y. Yamashita, K. Mori, R.L. Peterson, T. Leedham, J. Rickard and H. Sirringhaus, Nat. Mat. 10, 45-50 (2011).

[2] M.C. Gwinner, Y. Vaynzof, K.K. Banger, P.K.H. Ho, R.H. Friend and H. Sirringhaus, Adv. Funct. Mat. 20, 3457-3465 (2010)

 Date: 21/November/2014 – (Friday) – Place: Sala 212 – Auditório do Departamento de Física– Time: 10h15min

THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar: 

Studies of Dipolar Bose-Einstein condensates in optical lattices 

Prof. Dr. Emanuel Alves de Lima Henn – Instituto de Física de São Carlos / USP

Abstract:

 In this talk we discuss some aspects of a strongly dipolar, Chromium Bose-Einstein condensate in an optical lattice, focusing on its stability and in the observed confinement induced-collapse of the condensate when release from the trap. Optical lattices are rich playgrounds for dipolar BECs since this environment brings into play the interplay between short and long range interactions and, if suitably tailored, make the dipolar BEC much more stable, bringing it closer to reveal some interesting and new phases predicted theoretically. In this talk we show the first measurements of the stability of a dipolar BEC in an optical lattice and also the phenomena of dipolar collapse induced by a change in the cloud geometry. We also discuss new perspectives in the field of dipolar quantum gases.

Date: 14/November/2014 – (Friday) – Place: Sala 212 – Auditório do Departamento de Física– Time: 10h15min