Past Seminars
Thursday, September 04 at 4:00pm (Dow 107)
Prof. Pastori Parravicini, Dept. of Physics "A. Volta", University of Pavia (Italy)
Graphene: A Fascinating Material from the Two-Dimensional World
Graphene, a monolayer of carbon atoms on the honeycomb topology, is emerging as a solid-state reservoir of massless Dirac fermions, and related quantum electrodynamics phenomena. Graphene provides a rich unconventional phenomenology, with relevant perspectives both in fundamental physics and in technological aspects.
The electronic structure and the current profiles of graphene ribbons are investigated within the Keldysh nonequilibrium formalism in the tight-binding framework. Simulations of charge transport in field-effect controlled graphene ribbons highlight the striking transport properties of carriers controlled by the Dirac points in the low energy region; these include minimal conductivity, diffusive shot noise, Klein tunneling, half-integer relativistic quantum Hall effect, current profiles, valley-valve filtering effect. Manipulations with magnetic fields and gate voltages of the electron-hole nature of carriers, intervalley scattering and current flow, open perspectives for the development of unconventional carbon devices based on charge conjugation symmetry of Dirac particles.
download as pdf
Host: Marco Fornari
Thursday, September 18 at 4:00pm (Dow 107)
Deptartment of Physics, Central Michigan University
DEPARTMENTAL JAMBOREE
- Prof. Alan Jackson: Far from crystals: Theoretical studies of glasses and atomic clusters.
- Prof. Andy Sieradzan: Atomic physics using laser spectroscopy.
- Prof. Marco Fornari: Materials for energy conversion: Design rules from first principles.
- Prof. Chris Tycner: Observational stellar astrophysics.
Host: Juan Peralta
Cookies and coffee @ 3:30pm in Dow 201.
Wednesday, September 24 (Dow 109)
Jan Fiala, Department of Physics, Central Michigan University
Mathematica 6: What is new and useful for teaching, studying, and research?
This seminar provides an introduction to some of technologies in Mathematica 6 and their applications across disciplines. Topics covered include numeric and symbolic computations, programming, working with data, visualization, creating technical documents, dynamic interactivity, and connection technologies. My presentation will follow closely the online seminar provided by Wolfram called A Technical Overview of Mathematica, but my objective will be the use of Mathematica for teaching and studying. In addition I will present examples of demonstrations in Physics and Mathematics.
Prerequisites: No background or previous experience with Mathematica is required to attend this seminar.
download notebook (and change the extension from .txt to .nb)
Thursday, October 02 at 4:00pm (Dow 107)
Artemis Spyrou, National Superconducting Cyclotron Laboratory, Michigan State University
Studying Nuclear Reactions to Understand the Stellar Cauldrons
During the past decades, major effort was devoted to the understanding of the processes which are responsible for the synthesis of all elements found in the cosmos. Although much more is now known about the different mechanisms and stellar environments where nucleosynthesis could take place, there are still many open questions that need to be resolved. One of the puzzles of astrophysical models is the production of a group of proton rich nuclei, the so called p nuclei. The term p nuclei refers to 35 stable nuclides, in the mass region between Se (Z=34) and Hg (Z=80), which are 10-100 times less abundant than their more neutron rich neighbors. These rare nuclei are not produced by the two neutron processes that create all other nuclides beyond iron. Instead, a different mechanism was proposed for their synthesis called the p process. In this talk a description of the possible p-process scenarios and the discrepancies between the predicted and the observed abundances of the p nuclei will be presented. The main focus will be the nuclear physics contribution to the p-process modeling. In particular, different experimental techniques will be described as well as resent results.
download as pdf
Host: Joe Finck
Cookies and coffee @ 3:30pm in Dow 201.
Thursday, October 16 at 4:00pm (Dow 107)
Chih-Wei Lai, Deptartment of Physics, Michigan State University
Condensation of Excitons and Exciton-Polaritons in Semiconductor Nanostructures
Excitons, the solid state analogue of the hydrogen atom or of positronium, have played a significant role in elucidating the optical properties of solids. The current interest in exciton physics is due to the possibility of creating novel nanoscale semiconductor structures of reduced dimensionality. In these systems, quantum size effects dramatically reshape the many-body interactions; therefore, these systems are ideal test beds for understanding quantum collective phenomena such as Bose-Einstein condensation (BEC). In particular, due to the light effective mass, excitons are expected to undergo BEC at a temperature six order of magnitude higher than that of atomic BEC. In planar semiconductor microcavities, the strong coupling between the microcavity photons and quantum well excitons further leads to the formation of quasiparticles know as exciton-polaritons. I will review key developments on the exciton and exciton-polariton condensations in semiconductor nanostructures. Specifically for exciton-polariton systems, I will report the following experimental observation of collective effects: (1) first and second order coherence, (2) Bogoliubov-like excitation spectra, (3) polarization properties of the condensates, and (4) coherent zero-state and pi-state in an exciton-polaritonic lattice.
References:
- Coherent zero-state and p-state in an exciton-polariton condensate array, Nature 450, 529 (2007).
- Observation of Bogoliubov excitations in exciton-polariton condensates, Nature Physics 4, 700 (Sep 2008)
download as pdf
Host: Juan Peralta
Cookies and coffee @ 3:30pm in Dow 201.
Thursday, October 23 at 4:00pm (Dow 107)
Charles I. Sukenik, Department of Physics, Old Dominion University
Photoassociative Spectroscopy of Trapped Ultracold Atoms
Photoassociative spectroscopy, the probing of free-bound transitions with high resolution, has proven to be a powerful tool in the ultracold regime. At ultracold temperatures, the low translational energy and narrow thermal distribution of the colliding atoms allow vibrational and rotational structure of molecular spectra to be clearly resolved, even close to the dissociation limit. In this talk, we will discuss recent results of photoassociative spectroscopy performed on colliding ultracold metastable-state argon atoms confined in a magneto-optical trap and present measurements of the collisional trap loss resulting when ultracold rubidium atoms are simultaneously confined with the argon. We will also discuss our findings of an investigation to spatially confine ultracold rubidium atoms in a pulsed optical dipole force trap. We will conclude with a brief discussion of future directions of the research, including spectroscopy of purely-long range molecular states of the krypton dimer.
download as pdf
Host: Andy Sieradzan
Cookies and coffee @ 3:30pm in Dow 201.
Thursday, October 30 at 4:00pm (Dow 107)
Nicola Bonini, Department of Materials Science and Engineering, Massachusetts Institute of Technology
Transport Properties of Carbon Nanostructures from First-Principles
Carbon forms a variety of stable structures, from precious diamond to inexpensive graphite. Surprisingly, it is the latter that excites scientists the most. The reason is that graphene, a single layer of graphite, and nanotubes, rolled-up graphene, are unique low-dimensional systems that show exceptional physical properties. For example, they have the highest thermal conductivities ever reported and they exhibit outstanding electron transport properties, that make them very promising materials for future technological applications. In this talk, I will review the main results of our first-principles calculations of the electronic and vibrational properties of these systems. In particular, I will discuss our results on the electron-phonon and phonon-phonon interactions, which are the key ingredients to understand the energy relaxation mechanisms in these systems and control their transport properties.
download as pdf
Host: Marco Fornari
Cookies and coffee @ 3:30pm in Dow 201.
Thursday, November 13 at 4:00pm (Dow 107)
Don Morelli, Department of Chemical Engineering & Materials Science Michigan State University
Materials for Energy Conversion II:
What We've Done in the Lab
New theoretical approaches and first principles calculations (see for instance "Materials for Energy Conversion: Design Rules from First Principles" presented in this seminar series by CMU's Marco Fornari in September) have been introduced recently to guide the search for new materials with enhanced thermoelectric energy conversion efficiency. This talk will focus on our efforts to implement some of these new concepts in the laboratory. Thermoelectric efficiency increases with thermoelectric figure of merit Z = a2s/k, where a is the Seebeck coefficient, s the electrical conductivity, and k the thermal conductivity. Two distinct routes for increasing Z are thus i) thermal conductivity reduction; and ii) enhancement of the power factor a2s. We will present an overview of our work on several materials systems, including filled skutterudites, I-V-VI2 semiconductors, nanocomposites, and hybridization gap semiconductors, which are chosen with these design rules in mind and on which promising results have been demonstrated.
download as pdf
Host: Marco Fornari
Thursday, April 17 at 4:00pm (Dow 107)
Jacek Borysow, Department of Physics, Michigan Tech University
Quest for the Mass of Neutrino
or
Michigan & Texas Against the Rest of the World
"Discoveries involving neutrinos are reshaping the foundations of our understanding of nature. Two Nobel Prizes in physics recognized the detection of neutrinos coming from the Sun and from exploding stars. More recent underground neutrino experiments have excited scientific community with definite observations that neutrinos of different types transform into one another, implying that they have mass. Neutrinos have moved from obscurity onto center stage in astrophysics and in particle physics".
-National Research Council, NAS 2003
I will describe the joint Michigan Tech and The University of Texas anti-neutrino mass experiment (NEXTEX) that will resolve the electron anti-neutrino mass to at least 0.5 eV, by measuring the endpoint energy spectrum of the beta electrons from molecular tritium. The knowledge of the neutrino mass scale has significant impact on astrophysics and cosmology. Because the universe contains a huge number of neutrinos, their mass could be a significant fraction of the total mass of the universe. The neutrino masses could determine whether the universe will continue expanding or eventually collapse; so an unexpected additional mass could change current predictions of the fate of the universe. This seminar is a story about the pitfalls and the glory of the great experiment.
SIGMA-PI-SIGMA Reception to follow in Dow 231 after the talk.
Host: Andy Sieradzan
Thursday, March 20 4:00pm (Dow 107)
Dr. Dana E. Backman, SOFIA and the SETI Institute
Nearby Stars and Debris Disks: A Ringside Seat to Planet Formation
Astronomers have discovered disks of gas and dust around many young
stars that may be the sites of ongoing planet formation. Some
nearby older stars are surrounded by rings and disks of material
that are probably remnants of planet formation processes. These
so-called "debris disks" have sizes and structures resembling the
Kuiper Belt of icy objects orbiting beyond Neptune in our solar
system. Current observations of debris disks by Earth- and
space-based observatories will be reviewed, including signs of the
gravitational influence of large planets on the disk morphologies.
Future observations of these systems by SOFIA (Stratospheric
Observatory for Infrared Astronomy) are expected to provide better
evidence of the presence of planets associated with the debris disks.
Host: Chris Tycner
-
Wednesday, March 19 7:00pm (Dow 171)
Dr. Dana E. Backman, SOFIA (Stratospheric Observatory for Infrared Astronomy) and the SETI Institute
Harlow Shapley Public Astronomy Lecture:
Looking for Life in All the Right Places: An Astrobiological Tour of the Solar System
As soon as the Copernican revolution made humanity aware that the
Earth is one planet among many, speculation began about the
possibility that other planets might be inhabited. The main focus of
interest always has been Mars, with the most Earth-like surface
conditions of any planet. Rovers Spirit and Opportunity have found
clear evidence that Mars was once wetter and warmer than at present.
In addition, Viking Mars lander soil test results from the 1970s
indicated possible biological activity, and some investigators believe
Mars rock ALH84001 contains fossil microbes plus their metabolic
products. Beyond Mars, there is evidence for liquid water under ice
crusts on Jupiter's moons Europa and Ganymede and Saturn's moon
Enceladus, as well as abundant organic compounds in the atmosphere and
on the surface of Saturn's moon Titan. Could any of these worlds
harbor Earth-like, water-and-carbon-based life? Astrobiology research
and planetary exploration may reveal answers within just a few
decades.
Host: Chris Tycner
-
Thursday, February 28 4:15pm (Dow 107)
Veronica Barone, Department of Physics, Central Michigan University
Graphene Nanoribbons: The Rising Star in Nanomaterials Research
Graphene-based materials have emerged as one of the most promising candidates for the new generation of electronic devices. Here, we will discuss the rich variety of electronic properties displayed by different types of the so-called graphene nanoribbons. These ribbons are narrow strips of graphene that exhibit electronic behavior similar to that of carbon nanotubes. However, unlike nanotubes, carbon nanoribbons can be produced in a much more controllable manner. Despite this great advantage, their exotic electronic and magnetic properties depend strongly on the nature of the edges that are characteristic of these systems. We will present results of our first-principles calculations of the electronic properties of these materials, considering pristine and functional groups at the edges. We will also explore the electronic properties of other multi-component hexagonal networks.
Host: Juan Peralta
Cookies and coffee: 3:45pm in Dow 201.
-
Thursday, February 07 4:00pm (Dow 107)
Dr. Erika Grundstrom, Vanderbilt University
RY Scuting Along: Studying a Messy Binary
A long time ago in a binary far, far away, one star was growing while another was shrinking. Even though this actually happened 7000 years ago, the light from these events in the RY Scuti binary is just getting to us. Right now we see one star dumping some of its mass onto its companion - active mass transfer and a messy transfer at that. I'll show you how we gleaned information about the two stars (such as masses) and determined that there is a 2000 A.U. double-ring nebula and a 1 A.U. circumbinary disk around the two stars, gas leaking from L2, and an accretion torus around the mass gainer. Eventually, one or both of these stars will go supernova.
Host: Chris Tycner
-
Thursday, January 10 4:00pm (Dow 107)
Krzysztof Starosta, Michigan State University
Recoil Distance and Doppler Shift Attenuation Lifetime Measurements at NSCL
Transition rate were measured recently for the first and the second 2+ states in N=Z 64Ge, far from the line of nuclear stability. The experimental results are in excellent agreement with large-scale Shell Model calculations applying the recently developed GXPF1A interactions. The measurement was done using the Recoil Distance Method (RDM) and a unique combination of state-of-the-art instruments at the National Superconducting Cyclotron Laboratory (NSCL). States of interest were populated via an intermediate-energy single-neutron knock-out reaction. RDM and related Doppler Shift Attenuation studies of knock-out and fragmentation reaction products hold the promise of providing lifetime information for excited states in a wide range of unstable nuclei. Physics applications of both methods will be presented and discussed.
Host: Mihai Horoi
Thursday, March 20 4:00pm (Dow 107)
Dr. Dana E. Backman, SOFIA and the SETI Institute
Nearby Stars and Debris Disks: A Ringside Seat to Planet Formation
Astronomers have discovered disks of gas and dust around many young stars that may be the sites of ongoing planet formation. Some nearby older stars are surrounded by rings and disks of material that are probably remnants of planet formation processes. These so-called "debris disks" have sizes and structures resembling the Kuiper Belt of icy objects orbiting beyond Neptune in our solar system. Current observations of debris disks by Earth- and space-based observatories will be reviewed, including signs of the gravitational influence of large planets on the disk morphologies. Future observations of these systems by SOFIA (Stratospheric Observatory for Infrared Astronomy) are expected to provide better evidence of the presence of planets associated with the debris disks.
Host: Chris Tycner
Wednesday, March 19 7:00pm (Dow 171)
Dr. Dana E. Backman, SOFIA (Stratospheric Observatory for Infrared Astronomy) and the SETI Institute
Harlow Shapley Public Astronomy Lecture:
Looking for Life in All the Right Places: An Astrobiological Tour of the Solar System
As soon as the Copernican revolution made humanity aware that the Earth is one planet among many, speculation began about the possibility that other planets might be inhabited. The main focus of interest always has been Mars, with the most Earth-like surface conditions of any planet. Rovers Spirit and Opportunity have found clear evidence that Mars was once wetter and warmer than at present. In addition, Viking Mars lander soil test results from the 1970s indicated possible biological activity, and some investigators believe Mars rock ALH84001 contains fossil microbes plus their metabolic products. Beyond Mars, there is evidence for liquid water under ice crusts on Jupiter's moons Europa and Ganymede and Saturn's moon Enceladus, as well as abundant organic compounds in the atmosphere and on the surface of Saturn's moon Titan. Could any of these worlds harbor Earth-like, water-and-carbon-based life? Astrobiology research and planetary exploration may reveal answers within just a few decades.
Host: Chris Tycner
Thursday, February 28 4:15pm (Dow 107)
Veronica Barone, Department of Physics, Central Michigan University
Graphene Nanoribbons: The Rising Star in Nanomaterials Research
Graphene-based materials have emerged as one of the most promising candidates for the new generation of electronic devices. Here, we will discuss the rich variety of electronic properties displayed by different types of the so-called graphene nanoribbons. These ribbons are narrow strips of graphene that exhibit electronic behavior similar to that of carbon nanotubes. However, unlike nanotubes, carbon nanoribbons can be produced in a much more controllable manner. Despite this great advantage, their exotic electronic and magnetic properties depend strongly on the nature of the edges that are characteristic of these systems. We will present results of our first-principles calculations of the electronic properties of these materials, considering pristine and functional groups at the edges. We will also explore the electronic properties of other multi-component hexagonal networks.
Host: Juan Peralta
Cookies and coffee: 3:45pm in Dow 201.
Thursday, February 07 4:00pm (Dow 107)
Dr. Erika Grundstrom, Vanderbilt University
RY Scuting Along: Studying a Messy Binary
A long time ago in a binary far, far away, one star was growing while another was shrinking. Even though this actually happened 7000 years ago, the light from these events in the RY Scuti binary is just getting to us. Right now we see one star dumping some of its mass onto its companion - active mass transfer and a messy transfer at that. I'll show you how we gleaned information about the two stars (such as masses) and determined that there is a 2000 A.U. double-ring nebula and a 1 A.U. circumbinary disk around the two stars, gas leaking from L2, and an accretion torus around the mass gainer. Eventually, one or both of these stars will go supernova.
Host: Chris Tycner
Thursday, January 10 4:00pm (Dow 107)
Krzysztof Starosta, Michigan State University
Recoil Distance and Doppler Shift Attenuation Lifetime Measurements at NSCL
Transition rate were measured recently for the first and the second 2+ states in N=Z 64Ge, far from the line of nuclear stability. The experimental results are in excellent agreement with large-scale Shell Model calculations applying the recently developed GXPF1A interactions. The measurement was done using the Recoil Distance Method (RDM) and a unique combination of state-of-the-art instruments at the National Superconducting Cyclotron Laboratory (NSCL). States of interest were populated via an intermediate-energy single-neutron knock-out reaction. RDM and related Doppler Shift Attenuation studies of knock-out and fragmentation reaction products hold the promise of providing lifetime information for excited states in a wide range of unstable nuclei. Physics applications of both methods will be presented and discussed.
Host: Mihai Horoi
Physics Department
| Phone: 989-774-3321 | 203 Dow Hall