Fall 2016

It’s All About Water

Speaker(s): 
Peter Hamm
Dates: 
Thursday, October 13, 2016 - 4:00pm to 5:00pm

Ultrafast time-resolved spectroscopy, and in particular its extension to multidimensional techniques, can tell us a lot about solvation dynamics, structural dynamics and energy transfer processes of solution phase molecular systems. I will illustrate applications of these spectroscopies by discussing a couple of quite diverse examples that lie at the interface between Physics, Biology and Chemistry. In different ways, these examples highlight the importance of water as a very special substance. That is, I will start out with the ultrafast structural dynamics of...

Quantum Mechanics, Chemical Space, and Machine Learning

Speaker(s): 
O. Anatole von Lilienfeld
Dates: 
Thursday, September 29, 2016 - 4:30pm to 5:30pm

Many of the most relevant chemical properties of matter depend explicitly on atomistic details, rendering a first principles approach mandatory. Alas, even when using high-performance computers, brute force high throughput screening of compounds is beyond any capacity for all but the simplest systems and properties due to the combinatorial nature of chemical space, i.e. all compositional, constitutional, and conformational isomers. Consequently, efficient exploration algorithms need to exploit all implicit redundancies present in chemical space. I will discuss...

Many Body Localisation with Weak Disorder in the Quantum East Model

Speaker(s): 
Philip Crowley
Dates: 
Thursday, September 22, 2016 - 4:00pm to 6:00pm

Recent research has shown the Many-Body Localised phase to be a robust state of matter, thus furthering renewed interest in the quantum dynamics of closed systems. The existence of this non-thermalising phase is now well established in sufficiently low-dimensional and disordered systems. However the possibility of a many-body localised phase in the absence of static disorder remains an interesting prospect.

We study a kinetically constrained spin model with a putative disorder-free localisation transition and characterise the different...

Electron-electron Interaction Physics in Two-dimensional Materials

Speaker(s): 
Allan MacDonald
Dates: 
Monday, October 17, 2016 - 4:30pm to 6:00pm

Two-dimensional (2D) materials are interesting in part because their electron density can be varied in situ by transferring charge from nearby metallic layers, and because 2D materials can be stacked in a wide variety of configurations to achieve quite different physics properties. My talk will explain several theoretically imagined examples of electron-electron interaction physics in 2D materials, some of which have already been realized experimentally. I will briefly discuss spatially-indirect exciton condensate superfluids in transition metal dichalcogenides...

Decoherence and Flux Noise in Fluxonium-based Qubits

Speaker(s): 
Angela Kou
Dates: 
Thursday, October 13, 2016 - 4:00pm to 5:00pm

Superconducting qubits are created by connecting Josephson junctions, which are non-linear, non-dissipative elements,to simple electrical circuits. In this talk, I will give a brief introduction to the fluxonium qubit, which is a Josephson junction connected to a superinductance. I will then introduce an artificial molecule, composed of two strongly coupled fluxonium atoms, which possesses a tunable magnetic moment. Using an applied external flux,we can tune the molecule between two regimes: one in which the ground-excited state manifold has a magnetic dipole...

Skyrmion in Helimagnets

Speaker(s): 
Jiadong Zhang
Dates: 
Thursday, September 29, 2016 - 4:30pm to 5:30pm

Common magnets, such as refrigerator magnets and recorded bits in your hard disk, have aligned magnetic moments as compelled by the exchange interaction that causes ferromagnetism in the first place. Helimagnets are new types of magnets that exist in materials with broken inversion (non-centrasymmetric) symmetry, which enables the Dzyaloshinskii-Moriya interaction (DMI) to favor moments to be perpendicular to each other.  As a result of the competition, the ground state of a helimagnet is a spin helix and equally fascinating, the existence of skyrmion in...

Embedding Ground and Excited States in Real and Imaginary Time

Speaker(s): 
Michele Pavanello
Dates: 
Tuesday, September 27, 2016 - 2:30pm to 3:30pm

Over the past four years the Pavanello Research Group has developed an array of density embedding methods for the description of periodic and molecular systems alike, their Born-Oppenheimer adiabatic dynamics, as well as nonadiabatic Ehrenfest dynamics. The overarching goal of this effort has been to allow first principle simulations to approach realistic time- and length-scales, and to shed light on the dynamical behavior of complex systems. Our theory development has resulted in a new open-source density embedding software called embedded Quantum-ESPRESSO –...

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