Fall 2019

Swanson Engineering faculty promotions

  • By Jenny Stein
  • 2 October 2019

The Autumnal Equinox ushers in a season of welcome changes in the Swanson Engineering Department, in the form of faculty promotions! Congratulations to Giannis Mpourmpakis and John Keith for their promotions and to Karl Johnson, Chris Wilmer, and Susan Fullerton for receiving the William Kepler Whiteford Professorship, William Kepler Whiteford Fellowship, and Bicentennial Board of Visitors Faculty Fellowship, respectively.

Phase-change photonics for all-optical memory, computation, and beyond

Dr. Nathan Youngblood
Wednesday, October 2, 2019 - 12:00pm

Phase-change chalcogenides (such as AgInSbTe and Ge2Sb2Te5) have been used commercially as an optical storage medium in the last few decades owing to their high optical contrast and long-term stability, but only recently has a fully integrated photonic device been demonstrated. This approach not only enables all-optical memory on-chip, but also allows multilevel data storage with improved SNR, low switching energy, and high speed operation. In the first part of this talk, new innovations in phase-change, non-volatile photonic memory will be presented, including their use for “in-memory”...

Chromophore Packing and Singlet Fission Rates

Josef Michl
Thursday, December 5, 2019 - 4:00pm

Results of a theoretical examination of the effect of crystal packing on singlet fission (SF) rate are presented.  For a model system (pair of ethylenes) and several known or suspected SF materials: tetracene (1), cibalackrot (2), and 1,3-diphenylisobenzofuran (3), we predict molecular pair arrangements that are especially favorable for the rate of SF.  The predictions are obtained from an approximate evaluation of squares of SF eectronic matrix elements, based on a complete search of all possible pair packing geometries.  This is refined by an evaluation of...

Don't Cry Over Spilled Entropy

Stefano Curtarolo
Friday, October 4, 2019 - 11:30am

Critical understanding of large amount of data exposes the unavoidability of disorder and leads to new descriptors for discovering entropic materials. The formalism, based on the energy distribution spectrum of randomized calculations, captures the accessibility of equally-sampled states near the ground state and quantifies configurational disorder capable of stabilizing high-entropy homogeneous phases. The methodology - applied to disordered refractory 5-metal carbides (promising candidates for high-hardness, high melting point applications) – uncovers scientific surprises. Directions for...

Quantum quench and nonequilibrium dynamics in lattice-confined spinor Bose-Einstein condensates

Yingmei Liu
Monday, October 21, 2019 - 4:00pm

Bose-Einstein condensates (BECs) are ultra-cold gases, in which all atoms have a single collective wavefunction for their spatial degrees of freedom. With an additional spin degree of freedom, spinor BECs constitute a collective quantum system offering an unprecedented degree of control over such parameters as spin, density, temperature, and the dimensionality of the system. Spinor BECs have thus been considered as good quantum simulators for verifying and optimizing condensed matter models. In this talk, I will discuss a novel quantum phase transition realized in our antiferromagnetic...

Integrated Photonic Circuits for Classical and Quantum Information Processing

Qing Li
Wednesday, September 25, 2019 - 12:00pm

In addition to being the most successful material for electronics, silicon is also an excellent photonic material receiving widespread interest from both academia and industry. Following the tremendous success enjoyed by integrated electronics, integrated photonic circuits in silicon hold the promise of device scaling, mass fabrication, and system-level integration, which could revolutionize many traditional photonic technologies and create a wealth of practical applications. In this talk, I will provide several such examples focused on classical and quantum information processing. In the...

Superfluids of Light

David Snoke
Monday, October 14, 2019 - 4:00pm

It is possible to engineer the properties of photons in an optical medium to have an effective mass and repulsive interactions, so that they act like a gas of atoms. These "renormalized photons" are called polaritons. In the past decade, several experiments have demonstrated many of the canonical effects of Bose-Einstein condensation and superfluidity of polaritons. In this talk I will review some of this past work and present recent results with polaritons that have very long lifetime, including movies of equilibration and damped oscillations of a condensate.