## Events - Weekly

Sunday,
January 22 |
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Monday,
January 23 |

Tuesday,
January 24 |

Design and Construction of Oxide Heterostructures with Emergent Properties- Julia Mundy - UC Berkeley Materials systems with many strongly interacting degrees of freedom can host some of the most exotic physical ground states known. The subtle interplay of Coulomb interactions, electron-lattice coupling and spin/orbital ordering gives rise to phenomena as diverse as high-temperature superconductivity and topological insulating states as well as ferroelectricity and ferromagnetism. Many of these emergent ground states are found in perovskite oxide crystals where the close lattice matching across the series further permits abrupt heterointerfaces to be formed. Here I will show how advanced thin film deposition, in conjunction with analytical electron microscopy, can be used to engineer novel multifunctional complex oxide materials. In particular, I will discuss the design of the first material shown to be a strong magnetoelectric multiferroic at room-temperature, a promising candidate for low-power electronics in which electric fields control magnetic states. Jadwin A06 · 1:30 p.m.– 2:30 p.m. |

Wednesday,
January 25 |

Shining light on topological insulators and Weyl semimetals - Liang Wu, Berkeley The last decade has witnessed an explosion of research investigating the role of topology in band-structure, as exemplified by the wealth of recent works on topological insulators (TIs) and Weyl semimetals (WSMs). In this talk I hope to convince you that optical probes of solids give unique insight into these topological states of matter. First, I will discuss how we can probe the special low-energy electrodynamics of 3D TI thin films of Bi2Se3 using time-domain THz spectroscopy[1]. I will then discuss our work following the evolution of the response as a function of magnetic field from a semi-classical transport regime [2] to a quantum regime [3]. In the later case, although DC transport is still semi-classical, we find evidence for Faraday and Kerr rotation angles quantized in units of the fine structure constant [3]. This is consistent with the long-sought axion electrodynamics and the topological magneto-electric effect of 3D TIs. Among other aspects this give a purely solid-state measure of the fine structure constant based on a topological invariant [3]. I will also discuss how optics can observe quantized Hall conductance without involving the edge states [3]. Finally, I will present our most recent discovery of the largest 2nd harmonic generation in transition monopnictide Weyl semimetals such as TaAs [4] and talk about a new perspective of nonlinear optics in term of probing the Berry connection/curvature in momentum space [4]. (The focus of my talk will be on Refs. [3, 4].) 1.Wu, et al, Nat. Phys. 9, 410-414 (2013). 2.Wu, et al, Phy. Rev. Lett. 115, 217602 (2015). 3. Wu, et al, Science 354, 1124-1127 (2016). 4. Wu, et al, Nat. Phys. (2016). doi:10.1038/nphys3969 Jadwin A06 · 1:30 p.m.– 2:30 p.m. |

Thursday,
January 26 |

Friday,
January 27 |

Superconducting Quantum Electronics - Eli Levenson-Falk - Berkeley Superconducting materials enable the creation of novel electronics with fundamentally non-classical behavior. These quantum circuits can be used as detectors, magnetic field sensors, artificial atoms, and quantum bits, with applications ranging from chemistry to cryptography to studies of basic quantum mechanics. Fully realizing this potential requires us to cleverly design our circuits and experiments, to improve the performance of the basic circuit elements themselves, and to engineer scale-able systems. This work goes hand-in-hand with fundamental physics research, as each incremental improvement in performance opens up new experimental avenues. In this talk I will present some results from my own work tackling these practical challenges for applied and basic research, including studies of quasiparticle behavior in superconducting resonators and development of novel quantum-limited readout schemes. Jadwin A06 · 2:30 p.m.– 3:30 p.m. |

Saturday,
January 28 |