Colóquios do Departamento

Colóquios do DF - Realizados em 2015/2016


Quarta-feira dia 8 de Junho, às 16h30m

"The bright side of dark matter"


Orador: Nuno Peres, Universidade do Minho, Braga

Local: Anfiteatro PA2, Pav. Matemática, IST


ABSTRACT:

The basic aspects of the elementary physics of graphene plasmonics will be analysed in detail. The case of a single and double layer will be discussed. A model for the case of a periodic array of ribbons will be developed and compared with the experimental results. Some simple graphene nano-structures are briefly discussed.


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Quarta-feira dia 25 de Maio, às 16h30m

"The bright side of dark matter"


Orador: Ilídio Lopes, CENTRA - Instituto Superior Técnico

Local: Anfiteatro PA1, Pav. Matemática, IST


ABSTRACT:

Dark matter is now identified as being an invisible substance made of non-standard particles, that by the action of gravity alters the motion of stars and galaxies, bending the light emitted by distant luminous sources. This unknown matter makes almost 90% of the matter of our own Galaxy, similarly to the other galaxies in the Universe. In this talk, I start by reviewing the fundamental results that lead to the discovery of dark matter since more than 80 years ago. In the following, I discuss how the Sun and stars are used to study the properties of dark matter, either: to limit the number of proposed non-standard dark matter particle candidates, or as a template to study the impact of dark matter in the formation of the stars, stellar populations and galaxies in the early stages of the Universe.






Quarta-feira dia 18 de Maio , às 12h00m


"Detection and characterization of other planets: results from high resolution spectroscopy"


Orador: Nuno C. Santos, Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto

Local: Anfiteatro VA4, Pavilhão de Engª Civil, Piso -1, IST Alameda-campus


ABSTRACT:
As the number of known exoplanetary systems increases, the focus of exoplanet research is now pointed towards two major lines of research: i) the detection of very low mass planets, with the goal of finding an Earth sibling and understanding the frequency of Earths in our Galaxy, and ii) the detailed characterization of the planets, including their internal structure and atmospheres. New instrumentation projects are being developed towards these goals, using both ground- and space-based instrumentation. These efforts, led by the major international players (ESA, ESO, NASA) are driven by the long-lasting hope of detecting an Earth-like planet where life may have evolved.
In this talk I will review some of the major results in this field, with emphasis on those coming from high resolution spectroscopy. A focus will then be given to recent results we published regarding the detection of the reflected light spectrum from exoplanets. The potential of future instruments where our team is deeply involved will be discussed: the ESPRESSO and HIRES high resolution spectrographs (ESO VLT and E-ELT telescopes) and the CHEOPS and PLATO photometric missions (ESA).





Quarta-feira dia 11 de Maio, às 16h30m

"Clinical experience with the EDGE accelerator"


Oradora: Sandra Vieira, Department of Radiotherapy, Champalimaud Foundation, Lisbon

Local: Anfiteatro PA1, piso 01 do Pavilhão de Matemática, IST Alameda-campus


ABSTRACT:
The first clinical EDGE accelerator was installed in our department at the beginning of 2014. This accelerator is fully integrated with the Calypso and the Optical Surface Monitoring system (OSMS). A 6 Degree-of-Freedom couch is also a part of the assemble. Both Calypso and the OSMS are used to setup and monitor patient position during treatment. Using the Calypso system patient position is found with the help of beacon transponders whereas the OSMS relies on the surface of the patient. In this presentation a description of the EDGE clinical treatment delivery will be given. Patient cases treated at the EDGE with intensity beam modulation will also be shown including patient quality assurance procedures. Reasons for the increasing use of hypofractionated treatments (using 1, 3 or 5 treatment sessions) will also be discussed.







Quarta-feira dia 04 de Maio, às 16h30m


"Novel approaches in photovoltaics: Materials, devices and prospects"


Orador: Jorge Morgado, Organic Electronics Group, IT-LX

Local: Anfiteatro PA1, piso 01 do Pavilhão de Matemática, IST Alameda-campus


ABSTRACT:
Since the discovery of the photovoltaic effect, a significant effort has been made to develop the technology of the photovoltaic solar cells. Inorganic semiconductors, namely silicon, for a wider use, and compound semiconductors, for specific applications, have been the materials of choice. In this seminar I will describe the novel approaches that are being developed, with special emphasis on the new materials and fabrication techniques. I will also discuss the current limitations and possibilities of these new technologies.





Quarta-feira dia 13 de Abril, às 16h30m

"Microscopic black holes and (most) perfect fluid"


Orador: Elias Kiritsis, Universidade de Creta, Grécia

Local: Anfiteatro PA1, piso 01 do Pavilhão de Matemática, IST Alameda-campus


ABSTRACT:
Two tales will be told: The first involves Quantum Chromodynamics, the theory of the strong interaction. This theory is mostly intractable calculationally at low energies but was subjected over many years to a lot of experimental scrutiny. In the last 20 years, heavy ion experiments have provided a glimpse into a new phase of quark matter, that of the quark gluon plasma. On the other hand, a theoretical breakthrough relates strongly coupled gauge theories to string theories and gravity. Black holes are some of the strange beasts in such theories. The two approaches meet each other via a duality and they provide us with the opportunity to study (among other things) microscopic black holes in the laboratory.





Quarta-feira dia 06 de Abril, às 16h30m

"101 Years of General Relativity: From Cosmology to Black Holes and Fundamental Theories"


Orador: José Sande Lemos, Centro Multidisciplinar de Astrofísica - CENTRA, Departamento de Física, Instituto Superior Técnico

Local: Anfiteatro PA1, piso 01 do Pavilhão de Matemática, IST Alameda-campus


ABSTRACT:
General relativity was conceived in its final form in November 25, 1915, by Einstein. It is a geometrical spacetime theory of gravitation and matter. In this Colloquium, a presentation of the main aspects of general relativity, as well as its major implications in the past 101 years, namely, cosmology, black holes, and fundamental theories, will be presented. In the wake of the recent detection of gravitational waves due to black hole collision, there is a bright road ahead for the physics of the gravitational field. What the future holds for research in general relativity and gravitation will also be alluded to.





Quarta-feira dia 30 de Março, às 16h30m

"All-Electric Spintronics in Graphene"


Orador: Aires Ferreira, Department of Physics, University of York, United Kingdom

Local: Anfiteatro PA1, piso 01 do Pavilhão de Matemática, IST Alameda-campus


ABSTRACT:

Graphene—a one-atom thick layer of carbon atoms with unique electronic properties—is considered a promising candidate to implement novel electron-spin-based approaches to advanced storage and logic computing, an effort known as spintronics [1].

Recent evidence for giant spin–orbit coupling enhancement in graphene-based systems have opened up intriguing possibilities [2]. The presence of spin–orbit interactions in graphene is predicted to unlock a plethora of phenomena, including non-trivial Z2 topological phases [3]. Of particular interest is the spin Hall effect, a set of relativistic spin–orbit coupling phenomena whereby charge currents propagating in nonmagnetic materials generate spin currents and vice versa. In addition to their fundamental interest, spin Hall effects are a key ingredient in schemes for the manipulation and inter-conversion of spin and charge signals via pure electrical means, including spin Hall effect-induced spin–orbit torques at metal- ferromagnetic interfaces, and detection of spin currents generated from the spin Seebeck effect.

Theory predicts that dilute adatoms inducing short-range spin–orbit interactions in graphene can trigger a robust and gate-tunable spin Hall effect through the resonant skew scattering mechanism [4]. Recent experiments exploring non-local spin transport in H-bar graphene devices and spin pumping in graphene/magnetic insulator interfaces confirm the early theoretical predictions, paving the way for all- electric spintronics in two-dimensional carbon platforms [2,4].

This Colloquium will survey the rich interplay between intrinsic (topological) and extrinsic (disorder- related) mechanisms underlying the spin Hall effect in materials. The resonant scattering physics characteristic of two-dimensional massless Dirac fermions, and its importance to the giant spin Hall effect recently observed will be discussed. The solution of linear Boltzmann transport equations will be shown to disclose a hierarchy of relaxation times, accurately describing additional distortions of the Fermi surface due to spin–orbit coupling induced by extrinsic sources, such as adatoms [4].

The last part will discuss the intriguing role of bona fide quantum processes in the spin Hall effect, beyond Boltzmann transport theory. Based on calculations for a representative model system obtained through a nonperturbative diagrammatic treatment introduced recently [6], I will argue that a spin Hall effect induced by quantum coherent skew scattering is within reach the current state of the art.


1. W. Han et al. Nature Nanotech. 9, 794 (2014). M. Kamalakar et al. Nature Comm. 6, 6766 (2015)

2. J. Balakrishnan et al. Nat. Comm. 5, 4748 (2014); A. Avsar et al. Nat. Comm. 5, 4875 (2014); Z. Wang et al., Nat. Comm. 6, 8339 (2015). J. Mendes et al. Phys. Rev. Lett. 115, 226601 (2015)

3. C.L. Kane, and E.J. Mele, Phys. Rev. Lett. 95, 226801 (2005)

4. A. Ferreira et al. Phys. Rev. Lett. 112, 066601 (2014)
5. M. Milletari and A. Ferreira, arXiv pre-print: 1601.08076 (2016)





Quarta-feira dia 16 de Março, às 17h00m

"Gravitational waves: the sound of the universe"


Orador: Víctor Cardoso, CENTRA and Physics Department, IST

Local: Anfiteatro PA1, piso 01 do Pavilhão de Matemática, IST Alameda-campus


ABSTRACT:

A 14 de Setembro de 2015, às 09:50:45 UTC, os dois interferómetros LIGO detectaram um sinal de ondas gravitacionais provenientes da fusão de dois buracos negros. Esta descoberta histórica marca o nascimento da era da Astronomia de Ondas Gravitacionais, abrindo uma nova janela para o panorama do Universo Gravitacional, até agora invisível. Neste Colóquio será descrita a ciência envolvida nesta descoberta.






Quarta-feira dia 9 de Março, às 16h30m

"Valorização do Conhecimento: desafios e oportunidades"


Orador: José Carlos Caldeira, Presidente da Agencia Nacional de Inovação

Local: Anfiteatro PA1, piso 01 do Pavilhão de Matemática, IST Alameda-campus


ABSTRACT:
A valorização do conhecimento e a sua transferência entre os diversos agentes do Sistema Nacional de Inovação é um tema prioritário a nível nacional e internacional. A apresentação vai destacar alguns dos respetivos desafios e oportunidades, destacando as vertentes da cooperação e do financiamento


Quarta-feira dia 2 de Março, às 13h30m

"Diffusion"


Orador: Simone Calogero, Chalmers University of Technology

Local: Anfiteatro do Complexo Interdisciplinar, IST


ABSTRACT:
Diffusion is a type of motion which is observed in a variety of physical systems and at different scales. The applications are ubiquitous and range over fields as different as physics, biology, economics and social sciences. In this talk I will discuss some classical topics in diffusion theory, including Brownian motion and plasma dynamics, as well as its recent application to explain the nature of dark energy in Cosmology.








Colóquios do DF - Realizados no 1º Semestre de 2015/2016


Quarta-feira dia 9 de Dezembro, às 16h30m


"Neutrinos have mass! And so what?"


Orador: Filipe Rafael Joaquim, Departamento de Física & Centro de Física Teórica de Partículas, IST

Local: Anfiteatro VA3 (IST, Pavilhão de Civil)


ABSTRACT:
In this colloquium I will make a brief overview of theoretical aspects and open problems in Neutrino physics, and discuss the impact of the discovery of neutrino oscillations in our current understanding of fundamental interactions.




Quarta-feira dia 2 de Dezembro, às 16h30m

"Cloning the Higgs"


Orador: João Paulo Silva, Centro de Física Teórica de Partículas, IST

Local: Anfiteatro VA3 (IST, Pavilhão de Civil)


ABSTRACT:

CERNʼs LHC has recently discovered a spinless particle:the Higgs boson.
The electroweak and strong interactions are described by gauge groups, determining the number of spin 1 particles. The number of spin 1/2 families was determined by experiments at LEP, while nothing constrains the number of spin 0 particles. Determining their number and nature is a key problem in particle physics. Multi-Higgs models have many interesting features, which will be addressed here.





Quarta-feira dia 25 de Novembro, às 16h30m


"Magnetic tunnel junction devices and applications: from basic research to production"


Orador: Ricardo Ferreira, International Nanotechnology Laboratory, Braga

Local: Anfiteatro VA3 (IST, Pavilhão de Civil)


ABSTRACT:

Magnetoresistive devices and magnetic nanostructures are key building blocks in a large number of commercial electronic products across a wide range of applications covering industrial positioning sensors, automotive sensors, hard disk drive read heads and embedded memories. Simultaneously, the research around this type of structures and devices that explore pure spin currents and the interaction between charge currents and spin currents is very active. This creates an environment very favorable to the interaction between researchers and industry. With such a strong interaction the research, development and optimization process is very often driven by very practical questions related with the deployment of technological solutions in a production environment. How to optimize a device for a certain application, ensuring that it can be produced reproductively? How to scale up the production capacity? How to speed up the manufacturing process? How to characterize a process, rather than a single, isolated device?

This presentation will focus on the key developments carried out at INL during the last 4 years, including the development of high yield and high uniformity processes for the production of state-of-the-art magnetoresistive devices using CoFeB/MgO/CoFeB Magnetic Tunnel Junctions both at micrometric (100 μm down to 2 μm) and nanometric (down to 50 nm) scales.

Some applications and collaborative projects concerning the use of magnetic tunnel junctions as magnetic field sensors will be presented, including the current plans and activities to produce complex hybrid devices which integrate MTJs, MEMS, CMOS and more technologies.

A description of the current activities and projects concerning the development of Spin Transfer Nano-Oscillators will also be presented with a focus on the current efforts to improve the endurance of <1nm thin MgO tunnel barriers aiming the production of large amplitude homogeneous nano-oscillators and nano-oscillators excited with pure spin currents.





Quarta-feira dia 18 de Novembro, às 16h30m


Physical approaches for the study of insect embryo development"


Orador: Ivo Telley, Instituto Gulbenkian de Ciência

Local: Anfiteatro VA3 (IST, Pavilhão de Civil)


ABSTRACT:

Embryogenesis is a phase of animal development in which cells multiply and migrate to specific places of the embryo where they engage in a determined function. The earliest phase of embryo development is dedicated for cell and genome multiplication. A beautiful example of embryo development in which cellular entities are to be placed at specific locations is the insect, for example the fruit fly. After fertilisation the egg transitions into and embryo and undergoes several fast rounds of nuclear multiplication, in which the genome is duplicated and segregated, while the egg cell membrane does not divide. These nuclei are then positioned and anchored at the cell cortex, and within one hour several thousand cells are formed at once. To date, we do not know much about the mechanisms underlying the migration of nuclei during the first nine divisions. It is fascinating, however, that the micrometer sized nuclei travel almost a millimetre. The insect embryo is challenging to study under the microscope because it is rather large and filled with diffractive particles. Our group has adopted an explant approach, in which we reduce the volume of the embryo artificially, to study nuclear and cytoskeletal dynamics in explants of the early (0–90 min) Drosophila melanogaster fertilized egg and embryo.





Quarta-feira dia 11 de Novembro, às 16h30m


"From high-speed AFM to 4π holographic AFM"


Orador: Mervyn Miles, HH Wills Physics Laboratory, University of Bristol

Local: Anfiteatro VA3 (IST, Pavilhão de Civil)


ABSTRACT: Conventional AFM has limitations: (i) low imaging rate, (ii) probe-sample force interaction, and (iii) samples that are non-planar.

The vertical probe high-speed force microscope operates in non-contact and is based on shear- force microscopy (ShFM). In this HS ShFM [1], a vertically-mounted laterally-oscillating probe detects the sample surface ~1 nm from it as a result of the change in the mechanical properties of the water in confined geometry between the probe tip and the sample. With this technique, very low normal forces are applied to the specimen.

Conventional AFMs require planar samples because the probe raster scans in a plane. It is as if the tip is only ‘seeing’ the sample from above. We have overcome this limitation by steering the tip of a nanorod, fabricated with 2-photon polymerisation, in a 3D scan using holographic optical traps [2], in order to scan around a sample from any direction.

1. Fletcher J, Harniman RL, et al., Science 340 (2013) 595-599.

2. Phillips DB, et al., Nature Photonics 8 (2014) 400–405.




Quarta-feira dia 04 de Novembro, às 16h30m


"Luminescent wide bandgap nanomaterials"


Orador: Teresa Monteiro, Departamento de Física e I3N, Universidade de Aveiro

Local: Anfiteatro VA3 (IST, Pavilhão de Civil)


ABSTRACT: Low dimensional structures such as quantum wells, wires and nanoparticles are being increasingly used in our daily life in a wide range of technological applications with a tremendous impact in the global and societal needs.

Nitrides and oxides-based nanostructures with large bandgap energy are nowadays of upmost interest in lighting technologies and emergent luminescent based bio-applications. In both fields, several approaches can be followed to the materials’ growth/synthesis and doping aiming the tuning of the nanomaterials light emission with enhanced functionalities. For the desired applications, a deep knowledge of the materials optical properties should be thoroughly investigated to improve their efficiency and device development.

In this talk an overview of the luminescent properties of undoped and lanthanide doped nitrides (GaN-based) and oxides (ZnO, ZrO2) nanomaterials will be given. The nature of the defects from where the nanomaterials emission is originated will be discussed and explored in order to tailor the materials properties for solid state light and biological applications.




Quarta-feira dia 28 de Outubro, às 16h30m


"Pendulum clocks hanging from a wall: a synchronization mystery from Huygens"


Orador: Professor Luís Viseu Melo, Departamento de Física do Instituto Superior Técnico

Local: Anfiteatro VA3 (IST, Pavilhão de Civil)


In the XVII century Huygens observed the synchronization of two pendulum clocks hanging from a wall. We developed a model explaining this phenomenon, which is different from the problem of two clocks hanging from a moveable base. The data obtained in the laboratory are matched by the model and indicate that the communication between the clocks is done through sound pulses propagating in the wall.





Quarta-feira dia 21 de Outubro, às 16h30m


"A concise inventory of printable/flexible/stretchable sensors: technologies and applications for high volume applications"


Orador: Roger H. Grace, Roger Grace Associates

Local: Anfiteatro VA3 (IST, Pavilhão de Civil)



Quarta-feira dia 14 de Outubro, às 16h30m


"The 2015 Nobel Prize in Physics"


Orador: Heinrich Hoerber, Univ. Bristol, Reino Unido

Local: Anfiteatro VA3 (IST, Pavilhão de Civil)


The 2015 Nobel Prize in Physics was attributed to Takaaki Kajita and Arthur B. McDonald, "for the discovery of neutrino oscillations, which shows that neutrinos have mass". Kajita and McDonald have had leading roles in, respectively, the Super-Kamiokande (SK) and Sudbury Neutrino Observatory (SNO) experiments, that have solved the so-called "atmospheric neutrino anomaly" and "solar neutrino problem". With that, they have given huge insights into the fundamental nature of neutrinos.

After providing some general context, this seminar will describe the main challenges of the experiments and their results, briefly mentioning the portuguese participation in SNO.


It will conclude with the general picture of the consistency between the several experimental observations from many different sources, in the framework of three massive neutrinos, one of the most fascinating aspects of this field.