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Colloquia This Term

ics Colloquium
Friday, August 25, 2017
3:30 PM
Physics Building, Room 204

"Available"
ics Special Physics Forum for Faculty, Students, and Staff


Friday, September 1, 2017
3:30 PM
Physics Building, Room 203
Note special room.
Physics Forum
ics Colloquium
Friday, September 8, 2017
3:30 PM
Physics Building, Room 204
Tianran Chen [Host: Seunghun Lee]
UVA-Physics
"Origin of Long Lifetime of Band-Edge Charge Carriers in Organic-Inorganic Lead Iodide Perovskites"
ABSTRACT:

Long carrier lifetime is what makes hybrid organic-inorganic perovskites high performance photovoltaic materials. Several microscopic mechanisms behind the unusually long carrier lifetime have been proposed, such as formation of large polarons, Rashba effect, ferroelectric domains, and photon recycling. Here, we show that the screening of band-edge charge carriers by rotation of organic cation molecules can be a major contribution to the prolonged carrier lifetime. Our results reveal that the band-edge carrier lifetime increases when the system enters from a phase with lower rotational entropy to another phase with higher entropy. These results imply that the recombination of the photo-excited electrons and holes is suppressed by the screening, leading to the formation of polarons and thereby extending the lifetime. Thus, searching for organic-inorganic perovskites with high rotational entropy over a wide range of temperature may be a key to achieve superior solar cell performance.

ics Colloquium
Friday, September 15, 2017
3:30 PM
Physics Building, Room 204
Cass Sackett [Host: Joe Poon]
UVA-Physics
"Tune-out wavelength spectroscopy: a new technique to characterize atomic structure"
 
 Slideshow (PDF)
ABSTRACT:

When you shine a laser on an atom, the electric field of the light induces a dipole moment, resulting in an energy shift. The dipole can be either parallel or anti-parallel to the field, depending on the frequency of the light. This corresponds to negative or positive energies. At certain frequencies, however, the induced dipole is zero. The corresponding light wavelength is called a tune-out wavelength. The location of the various tune-out wavelengths depend on the electronic wave function in the atom, particularly the dipole matrix elements . So by measuring the tune-out wavelength, the dipole matrix elements can be determined more accurately than by conventional techniques. This is useful because the dipole matrix elements are also used to relate precision atomic experiments like parity violation to fundamental particle properties like the weak mixing angle. We have developed a new technique for measuring  tune-out wavelengths, which should improve our knowledge of many matrix elements by an order of magnitude or more. We hope that this will support new generations of precision atomic measurements.

SLIDESHOW:
ics Special Colloquium and Hoxton Lecture


Thursday, September 21, 2017
7:00 PM
Chemistry Building, Room 402
Note special date.
Note special time.
Note special room.
Nergis Mavalvala
M.I.T.
"The Warped Universe: the one hundred year quest to discover Einstein’s gravitational waves"
ABSTRACT:

In 2016, scientists announced the first ever detection of gravitational waves from colliding black holes, launching a new era of gravitational wave astrophysics. Gravitational waves were predicted by Einstein a hundred years earlier. I will describe the science, technology, and human story behind these discoveries that provide a window into some of the most violent and warped events in the Universe.

 

ics Colloquium
Friday, September 22, 2017
3:30 PM
Physics Building, Room 204
Nergis Mavalvala [Host: Cass Sackett]
M.I.T.
"Future directions in gravitational-wave detection"
ABSTRACT:

The Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves for the first time in 2015. Since then there have been a couple more detections of binary black hole mergers. I will discuss the instruments that made these discoveries, the science so far, and plans for future improvements and upgrades to LIGO. 

VIDEO:
ics Colloquium
Friday, September 29, 2017
3:30 PM
Physics Building, Room 204
Xiaochao Zheng [Host: Joe Poon]
UVA-Physics
"Peeling the Atomic Onion"
ABSTRACT:

The word "atom" (a-tomos) originates from ancient Greek philosophers, who argued that objects can be eventually divided into discrete, small particles, beyond which matter is no longer cuttable.  Our search for the answer to "What the matter is made of" has gone a long way, from the first experimental evidence of atoms in the 1800's, to Rutherford's alpha scattering on gold foils, to modern day's linear accelerators looking into the atomic nucleus. We now understand that matter is made of quarks and leptons, currently named elementary particles (objects of no size) that form the foundation of the Standard Model of Particle Physics. However, if we look back at this journey, one may wish to oppose the view of the ancient Greeks and argue that quarks and leptons cannot be the end of the story, that our quest for peeling the atomic onion may be a timeless journey.

I will discuss the frontier research in electron scattering at the GeV energy level. I will focus on parity violation in electron scattering off the proton and the neutron and the extraction of neutral-weak effective couplings between electrons and quarks, and show how such high precision measurements are now helping us venturing further into the study of subatomic structure. 

ics Colloquium
Friday, October 6, 2017
3:30 PM
Physics Building, Room 204
Kent Paschke [Host: Joe Poon]
UVA-Physics
"TBA"
ics Colloquium
Friday, October 13, 2017
3:30 PM
Physics Building, Room 204
Prem Kumar [Host: Olivier Pfister]
Northwestern University
"TBA"
ics Colloquium
Friday, October 20, 2017
3:30 PM
Physics Building, Room 204
Simonetta Liuti [Host: Joe Poon]
UVA-Physics
"Tomography of the Atomic Nucleus"
ics Colloquium
Friday, October 27, 2017
3:30 PM
Physics Building, Room 204
Avi Pe'er [Host: OSA/SPIE Student Chapter]
Bar Ilan University
"TBA"
ics Colloquium
Friday, November 3, 2017
3:30 PM
Physics Building, Room 204
Ted Hodapp [Host: Olivier Pfister]
APS Bridge Program
"TBA"
ics Colloquium
Friday, November 10, 2017
3:30 PM
Physics Building, Room 204
Vladimir Dobrosavljevic [Host: Gia-Wei Chern]
Florida State University
"TBA"
ics Colloquium
Friday, November 17, 2017
3:30 PM
Physics Building, Room 204

"Available"
ics Colloquium
Friday, December 1, 2017
3:30 PM
Physics Building, Room 204
Xiaoliang Qi [Host: Israel Klich ]
Stanford University
"TBA"
Colloquia and Special Lectures Committee
Cass Sackett (Chair)
Gordon Cates (Member)
Bob Hirosky (Member)
Bob Jones (Member)
Marija Vucelja (Member)
Nilanga Liyanage (Ex-Officio)

To add a speaker, send an email to cas8m@Virginia.EDU Include the seminar type (e.g. Colloquia), date, name of the speaker, title of talk, and an abstract (if available). [Please send a copy of the email to phys-speakers@Virginia.EDU.]