Seminar

The study of unconventional superconducting materials remains an active frontier of condensed matter physics. Exotic superconductivity, such as high T_C, topological, and heavy-fermion superconductors, often rely on phase sensitive measurements to determine the underlying pairing and/or the nature of novel excitations. In this talk I will detail the use of Josephson effect to detect novel properties of two multiband superconducting systems: NbSe₂ [1] and SnTe [2]. Focus will primarily be given modification of conventional Josephson effects due to the loss of time...

Additive manufacturing (AM), known as 3D Printing, has given rise to powerful capabilities for converting 3D digital models into physical objects. The valuable features of AM include the ability to build parts with tailored properties for custom applications, the high efficiency of material utilization, and the unprecedented flexibility for fabricating complex or intricated structures that cannot be made by traditional manufacturing processes. 

AM has been over 30 years old since its inception, and yet the technology is still a frontier with unexplored potentials partly due to the...

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”...

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...

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...

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...

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...

In the 5th century BCE, Zeno of Elea devised dozens of arguments against the possibilities of motion, change, and plurality. The loveliest of these, the Arrow Paradox, is briefly stated: "The flying arrow is motionless." In 1970, Wes Salmon published an anthology devoted to Zeno's Paradoxes and amply demonstrating their capacity to reward scrutiny from the perspectives afforded by mathematics and physics as they themselves move forward. Wes's introduction to that anthology was my first assignment in my first philosophy course. In 2019, I'll try to demonstrate that Zeno's paradoxes continue...