Applied Physics / Physics Colloquium

Applied Physics/Physics Colloquium

Topic: 
Novel Kondo Physics in Non-Kramers Doublets
Abstract / Description: 

Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.

Refreshments in the lobby of Varian Physics at 4:15 pm.

 

Autumn 2015/2016, Committee: A, Linde (Chair), S. Chu, P. Hayden, M. Schnitzer, L. Senatore

Date and Time: 
Tuesday, December 1, 2015 - 4:30pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
Physics and Applied Physics Annual Update
Abstract / Description: 

The "State of the Departments" colloquium is an annual update and welcome to our faculty, students, and friends, from the Chairs of the Physics and Applied Physics Departments.

Please note that the Paul Kirkpatrick Award will be announced at the start of this colloquium

Date and Time: 
Tuesday, September 29, 2015 - 4:15pm to 5:30pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium: Special Seminar

Topic: 
The Phases of Hard Sphere Systems
Abstract / Description: 

One of the simplest models of statistical mechanics is a system of identical hard sphere particles, placed inside a box whose energy and volume are free to fluctuate in response to an environment characterized by a temperature and pressure. A dimensionless pressure parameter p is formed from a combination of the sphere radius, the temperature, and the pressure of the environment. Qualitatively different average properties of the sphere packing are controlled by this dimensionless pressure: a "disordered" gas phase at small p and an "ordered" crystalline phase at large p. Since all (nonintersecting) sphere configurations are isoenergetic, the mechanism for crystalline ordering, called "order by disorder", is purely entropic in nature. Sphere packings having the highest possible density correspond to the limit of infinite p.


In addition to providing a physicist's intuition on the existence of phases in the hard sphere system, this tutorial talk will also touch on topics of mathematical interest. In the limit of many spheres (so "magic number" effects are minimized), does statistical mechanics distinguish among the different densest structures that arise in three dimensions? In higher dimensions, where much less is known, might we expect more than two phases, or perhaps just a single phase?

Applied Physics event page

Date and Time: 
Wednesday, April 22, 2015 - 4:00pm to 5:00pm
Venue: 
Building 380, Room 384-I

Applied Physics/Physics Colloquium: Advanced LIGO

Topic: 
Advanced LIGO: The Coming Dawn of Gravitational Wave Physics and Astronomy
Abstract / Description: 

For more than 50 years, scientists have endeavored to detect gravitational waves from galactic and extra-galactic compact astrophysical sources such as supernovae and merging neutron stars and black holes. Beginning in the 1960's, a series of ever more sensitive instruments were constructed to search for them. Alas, no gravitational waves have yet been found.

With Advanced LIGO coming online in 2015, we have good reason to believe that is about to change. In this colloquium I'll discuss gravitational waves, what makes them so interesting and challenging to detect, and how the Advanced LIGO interferometers will hunt for them. Gravitational wave science cuts across a broad swath of disciplines: general relativity, classical and quantum optics, materials science, and multi-messenger astronomy, so there should be something in the talk for everyone.

Date and Time: 
Tuesday, May 26, 2015 - 4:00pm to 5:00pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
Topological Insulators beyond Band Theory
Abstract / Description: 

Our appreciation of insulating states of quantum matter has been deepened in the last decade by the theoretical prediction and subsequent experimental discovery of topological insulators. Much of the theoretical discussion of these phases is informed by free electron band theory. In this talk, I will describe recent progress in generalizing the concept of topological insulation to strongly interacting electronic systems. I focus on a minimal generalization known as symmetry-protected topological (SPT) phases. Just like the familiar topological insulators, these states have a bulk gap and no exotic excitations, but have nontrivial surface states that are protected by symmetry. I will show how interactions enable many SPT phases for spin-orbit coupled three dimensional electronic insulators that have no analog in band theory. I describe their physical properties and experimental fingerprints. More generally, studies of such SPT phases represent possibly the simplest context for the interplay between interactions, symmetry, and topology in states of quantum matter. I will describe how the insights obtained provide fresh viewpoints on a number of other frontier theoretical problems in quantum condensed matter physics.

Date and Time: 
Tuesday, May 19, 2015 - 4:00pm to 5:15pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
Searching for the First Stars
Abstract / Description: 

Through observations of the CMB, we have a clear picture of the conditions in the universe at the point where atoms first combined and the universe became transparent. From deep observations of galaxies, we can study the universe at a z of ~ 6. Here, we find galaxies, smaller and more irregular than in our local universe, but recognizable as galaxies. In the critical period between recombination and z~6, the first stars and galaxies were born. Their radiation reionized the universe, and their nucleosynthetic products contaminated the interstellar matter from which later generations of stars would form with heavy elements. I will review the investigations that have searched for the diffuse light from this epoch, starting with total power observations such as those done by DIRBE on COBE to more recent observations of spatial correlations by the GSFC, Akiri, Irvine, and Caltech groups. There has been rapid progress in this research. Spatial correlations between the near IR emission and Chandra soft X-ray emission suggests an origin in energetic systems, while large scale spatial correlations seen in the near IR suggest an origin in stars stripped from galaxies. The next years will see these conflicts resolved and may reveal a first clear view into the concealed early history of the universe.

Date and Time: 
Tuesday, May 12, 2015 - 4:00pm to 5:00pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium

Topic: 
The Story of Single Molecules, from Early Spectroscopy in Solids to Super-Resolution Nanoscopy in Cells and Beyond
Abstract / Description: 

More than 25 years ago, low temperature experiments aimed at establishing the ultimate limits to optical storage in solids led to the first optical detection and spectroscopy of a single molecule in the condensed phase. At this unexplored ultimate limit, many surprises occurred where single molecules showed both spontaneous changes (blinking) and light-driven control of emission, properties that were also observed in 1997 at room temperature with single green fluorescent protein variants. In 2006, PALM and subsequent approaches showed that the optical diffraction limit of ~200 nm can be circumvented to achieve super-resolution fluorescence microscopy, or nanoscopy, with relatively nonperturbative visible light. Essential to this is the combination of single-molecule fluorescence imaging with active control of the emitting concentration and sequential localization of single fluorophores decorating a structure. Super-resolution microscopy has opened up a new frontier in which biological structures and behavior can be observed in live cells with resolutions down to 20-40 nm and below. Examples range from protein superstructures in bacteria to bands in actin filaments to details of the shapes of amyloid fibrils and much more. Current methods development research addresses ways to extract more information from each single molecule such as 3D position and orientation, in thick cells. Still, it is worth noting that in spite of all the focus on super-resolution, even in the "conventional" single-molecule tracking regime where the motions of individual biomolecules are recorded in solution or in cells rather than the shapes of extended structures, much can still be learned about biological processes.

Date and Time: 
Tuesday, April 28, 2015 - 4:00pm to 5:00pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium: Quantum Entanglement in Higher Dimensions

Topic: 
Quantum Entanglement in Higher Dimensions
Abstract / Description: 

2015 Robert Hofstadter Memorial Lecturer

Many fundamental experiments in quantum information have been performed with qubits, i.e. in rather low dimensional Hilbert spaces. Various experimental techniques have recently opened up discrete higher dimensions for experiments. These are particularly multi-mode interference and photon states with more complex wavefronts, like orbital angular momentum (OAM) states.

I will present some recent results focusing on OAM states and on verifications of entanglement in very high dimensions. So far, entanglement of quantum states with quantum numbers around 1,000 and of superposition in more than 100-dimensional Hilbert space have been realized. This may shed interesting light on the question of the quantum-classical transition. I will also discuss recent experiments for using some of these states in quantum communication with higher alphabets.

Entangled quantum states also provide novel ways for nonlocal imaging. Most recently, it was seen that one can obtain imaging where the photon interacting with the object does not even have to be detected. This exploits the fact that the phase of a product state cannot be localized.

Date and Time: 
Tuesday, April 21, 2015 - 4:00pm to 5:00pm
Venue: 
Hewlett 201

Applied Physics/Physics Colloquium: The Atacama Large Millimeter/submillimeter Array (ALMA) - Revealing New Chemical and Physical Views of the Cosmos

Topic: 
The Atacama Large Millimeter/submillimeter Array (ALMA) - Revealing New Chemical and Physical Views of the Cosmos
Abstract / Description: 

The Atacama Large Millimeter/submillimeter Array (ALMA) has already provided a new and exciting views of the Universe even before it has reached Full Science Observations. With the availability of both Science Verification data and PI data that are now publically available to the scientific community, we have only touched the surface of what is possible with the current array of ALMA capabilities. In this presentation, I will highlight the capabilities of this groundbreaking new facility which is providing order of magnitude improvements in sensitivity, resolution and bandwidth than any current astronomical observatory operating at these wavelengths. ALMA is open to wide variety of scientific investigation and has already challenged our current understanding of star and planet formation, investigations into general relativity and uncovered a molecular complexity in a variety of astronomical conditions that have no terrestrial counterpart. ALMA is capable of testing current physical and chemical theory in the most extreme environments imaginable. Finally, I will present an opportunity to get involved in the future of the ALMA observatory as it is constantly being expanded to meet the needs of the scientific community.

Date and Time: 
Tuesday, April 14, 2015 - 4:15pm to 6:00pm
Venue: 
Hewlett 201

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