In this talk, I will start from a general picture of light-matter interactions, such as quasiparticles and excitons, in solids and how to calculate them by first-principles approaches. Then I will focus on light-matter interactions of nanoscale materials, in which the reduced dimensionality substantially enhances many-electron interactions by orders of magnitude and results in unique excited-state properties, such as strongly polarized excitons and exciton liquids. By clarifying and calculating electron-electron, electron-hole, and electron-plasmon interactions, we can accurately explain many important measurements and provide new ideas to engineer light-matter interactions for exploring new science and realizing device and energy applications. Finally, beyond light-matter interactions, I will show how to combine different levels of first-principles tools and models to predict a wide range of electric and magnetic polarizations of solids and their applications.
Heisenberg’s uncertainty principle establishes a “standard quantum limit” of measurement precision that sets a bound on many precision measurements including atomic clocks and gravitational wave detectors. Using a special class of entangled quantum states known as squeezed states, it is possible to exceed the standard quantum limit. I will discuss our experiments investigating spin-1 atomic Bose-Einstein condensates in which non-equilibrium dynamical evolution creates spin-squeezed states with uncertainties an order of magnitude below the standard quantum limit. Additionally, we have developed novel quantum control techniques for the spin states and investigated Kibble-Zurek universality by quenching the spin system across a quantum phase transition. These experiments demonstrate new methods of manipulating out-of-equilibrium quantum systems, drawing together ideas from classical Hamiltonian dynamics and quantum squeezing of collective states.
We invite everyone to see the upcoming Transit of Mercury across the face of the Sun.
The inner planets (Mercury and Venus) can pass between the Earth and the Sun and, sometimes, they can be seen as little black dots traversing the face of the Sun over several hours. This is fairly rare for Mercury and very rare for Venus (next Venus transit is not till 2117). This is because although the two planets pass between the Earth and the Sun often, the planes of their orbit about the Sun do not coincide exactly with the plane of the Earth’s orbit around the Sun. Thus, most of the time, when they are directly between us and the Sun, they are a little above or a little below the solar disc. Once in a while the planes coincide and you can see the planets moving slowly (over the course of several hours) over the face of the Sun. The next time this will happen for Mercury is Monday, November 11th from 7:36 AM to 1:04 PM.
Weather permitting, we will be following this event from outside the Physics Building along Sanford Drive. We will set up a telescope with a solar filter so that the public will be able to safely view the event.
You cannot see the transit with the naked eye, and you must not look at the Sun either with the naked eye or with any optical equipment that is not equipped with the proper solar filters. We will be set up west of the Physics Building with a small telescope from about 9:30 AM (the transit will have already begun and Mercury will be silhouetted on the solar disc) until about 1:05 PM when the transit will have ended.
The next Mercury transit will not be until 2032, so come join us for this rare event!