Events List for the Academic Year

Event Time: Thursday, February 14, 2019 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar 2019-02-14T16:00:00 2019-02-14T17:00:00 3-minute thesis talks Event Information: Please come and support our students as they give 3-minute presentations of their thesis projects, as part of the international "3MT" competition! Event Location: Hennings 201
Event Time: Thursday, February 7, 2019 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar 2019-02-07T16:00:00 2019-02-07T17:00:00 TBD Event Location: Hennings 201
Event Time: Thursday, January 31, 2019 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar 2019-01-31T16:00:00 2019-01-31T17:00:00 TBD Event Location: Hennings 201
Event Time: Thursday, January 31, 2019 | 4:00 pm - 4:00 pm
Event Location:
Hennings 201
Add to Calendar 2019-01-31T16:00:00 2019-01-31T16:00:00 TBD Event Location: Hennings 201
Event Time: Thursday, January 31, 2019 | 2:00 pm - 3:00 pm
Event Location:
HENN 318
Add to Calendar 2019-01-31T14:00:00 2019-01-31T15:00:00 CM Seminar: Measurement and Control of Electron Dynamics Using THz Pulses Event Information: Phase-locked, few-cycle pulses of THz frequency light are powerful tools for both probing and driving ultrafast dynamics of low energy (meV scale) excitations in condensed matter. As an example of using THz pulses as a time-resolved probe, I discuss recent multi-THz spectroscopy experiments on the widely researched hybrid organometallic halide perovskites. These solution processable materials have been successfully applied to a variety of optoelectronic devices, most notably high efficiency photovoltaics achieving up to 22% power conversion efficiency in the lab (comparable to silicon). Their long carrier lifetimes and relative insensitivity of their electronic transport properties to the presence of impurities have been puzzling when considering their similarities to other direct band gap semiconductors like GaAs. This led to a proposal that charge carriers exist as large polarons, protected against scattering by their correlation to polar lattice vibrations. In this talk, I show ultrafast THz measurements provide direct evidence for the existence of polarons in these materials, resolving the quantum dynamics of their formation. In addition, strong field THz pulses can now be used to control the motion of charged particles on sub-cycle time scales. Along these lines, I will discuss our recent work on sub-cycle THz field emission of femtosecond electron wave packets from metal nanotips. We show that through field-assisted tunneling directly from the metal’s Fermi level, impressive electron bunch charges up to 106/shot are emitted on a sub-cycle time scale. These electrons are subsequently accelerated in the local THz field in the vicinity of the nanotip to keV energies over 100 nm length scales. We discuss possible applications as a source for single shot ultrafast electron diffraction and as a test bed for high field physics. Event Location: HENN 318
Event Time: Monday, January 28, 2019 | 3:00 pm - 4:00 pm
Event Location:
Hennings 318
Add to Calendar 2019-01-28T15:00:00 2019-01-28T16:00:00 CHIME results on Fast Radio Bursts Event Location: Hennings 318
Event Time: Thursday, January 24, 2019 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar 2019-01-24T16:00:00 2019-01-24T17:00:00 Symmetries in large scale structure, dark matter and black holes Event Information: We will discuss a few examples in cosmology and astrophysics where symmetries play an important role. First, we will show in what sense the dynamics of structure formation exhibits spontaneous symmetry breaking, and what it implies about the observed correlation functions. Second, we will explain the particle physics motivation for the idea that dark matter is an ultra-light pseudo-Goldstone boson, and explore its astrophysical implications. Lastly, if time permits, we will show how to construct an effective field theory of black hole perturbations based on symmetry considerations. Event Location: Hennings 201
Event Time: Thursday, January 24, 2019 | 3:00 pm - 4:00 pm
Event Location:
Hennings 318
Add to Calendar 2019-01-24T15:00:00 2019-01-24T16:00:00 Equity and Inclusion in PHAS Elections Event Information: Equity and Inclusion in PHAS Elections Time: 3:00 pm - 4:00 pm; Location: Hennings 318 https://equity-inclusion.phas.ubc.ca/2019/01/15/elections/ Event Location: Hennings 318
Event Time: Thursday, January 24, 2019 | 2:00 pm - 3:00 pm
Event Location:
BRIM 311, Stewart Blusson Quantum Matter Institute, 2355 East Mall
Add to Calendar 2019-01-24T14:00:00 2019-01-24T15:00:00 CM Seminar: CHIRAL ANOMALY AND CLASSICAL NEGATIVE MAGNETORESISTANCE OF WEYL METAL Event Information: We present a theory of magnetotransport phenomena related to the chiral anomaly in Weyl semimetals. We show that conductivity, thermal conductivity, thermoelectric and the sound absorption coefficients exhibit strong and anisotropic magnetic field dependences. In the presence of a magnetic field the Wiedeman-Franz law in these materials can be violated. We also discuss properties of magneto-plasmons and magneto-polaritons, whose existence is entirely determined by the chiral anomaly. Finally, we discuss the conditions of applicability of the quasi-classical description of electron transport phenomena related to the chiral anomaly. Event Location: BRIM 311, Stewart Blusson Quantum Matter Institute, 2355 East Mall
Event Time: Wednesday, January 23, 2019 | 1:00 pm - 2:00 pm
Event Location:
Henn 318
Add to Calendar 2019-01-23T13:00:00 2019-01-23T14:00:00 New Sources of Gravitational Radiation: The Black Hole Graviton Laser Event Information: Black holes admit quantum mechanical bound states of ultra light particles such axions or neutrinos.  These states can undergo quantum transitions absorbing or emitting gravitons. Graviton trajectories, in the particle picture, in principle can correspond to gravitons that orbit the black hole arbitrarily many times before finally escaping to infinity. Quantum mechanically, such graviton trajectories correspond to graviton-black hole scattering states which exhibit an arbitrarily large time delay before they emerge at infinity. The spontaneous emission of such graviton states coupled with their subsequent stimulated emission as the graviton circles around the black hole through the lasing medium, can in principle give rise to significant amplification. The observation of intense, monochromatic beams of coherent gravitons would then be a confirmation of the existence of ultra light massive particles and shed light on the properties of black holes. Event Location: Henn 318
Event Time: Monday, January 21, 2019 | 3:00 pm - 4:00 pm
Event Location:
Hennings 318
Add to Calendar 2019-01-21T15:00:00 2019-01-21T16:00:00 Radiation-Dominated Black Hole Accretion Flows Event Information: At high accretion rates, the outward force of radiation pressure generated by energy released by infalling matter can exceed the inward pull of gravity.  Such super-Eddington accretion flows occur in many systems, such as the inner regions of quasars and luminous AGN, ultra-luminous X-ray sources (ULXs), and tidal disruption events.  Understanding such flows is important not only for interpreting the spectra and variability of these sources, but also to predict the rate of growth of black holes in the early universe, and to quantify energy and momentum feedback into the medium surrounding the black hole, a process likely to be important in galaxy formation.  New results from a study of the magnetohydrodynamics of luminous accretion flows, in which radiation pressure dominates, will be presented. Our results reveal new physical effects, such as turbulent transport of radiation energy, that require extension of standard thin-disk models.  We discuss the implications of our results for the astrophysics of accreting black holes. Event Location: Hennings 318
Event Time: Thursday, January 17, 2019 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar 2019-01-17T16:00:00 2019-01-17T17:00:00 Ultrastrong coupling of a single artificial atom to the electromagnetic field Event Information: I will present our results on the observation of ultrastrong interactions between an artificial atom and a one-dimensional quantum electromagnetic field. In this new regime the atom-field interaction strength is comparable to or larger than the atomic frequency. We design a tunable coupling circuit between the atom, a flux qubit, and the electromagnetic field in a superconducting transmission line, which allows us to explore the transition from weak to ultrastrong coupling. The experiments rely on coherent measurements of scattering of microwaves by the atom. We observe a linewidth comparable to the atomic frequency, a clear signature of ultra-strong coupling. We also find that the atomic frequency is systematically smaller than the bare atomic frequency, in agreement with renormalization by the field.  In the second part of the talk I will discuss experiments in which we apply strong driving to the atom. We show that the driving amplitude can be used to change the threshold for the coherent to incoherent transition for atom dynamics, as observed spectroscopically and in agreement with theory. Finally, I will discuss prospects for the study of the atomic time dynamics in the ultra-strong coupling regime and its implications for investigations of open system physics, quantum optics, and relativistic quantum information. Event Location: Hennings 201
Event Time: Thursday, January 17, 2019 | 2:00 pm - 3:00 pm
Event Location:
311 - 2355 East Mall
Add to Calendar 2019-01-17T14:00:00 2019-01-17T15:00:00 CM Seminar: Coherent soft X-ray scattering and imaging of electronic textures in quantum solids Event Information: Strongly-correlated electron systems with competing collective electronic phases are often inherently granular. The spatial organization of the electronic degrees of freedom is essential to understand the phenomenology of these complex systems, yet there are currently no probes of the charge, spin, and orbital degrees of freedom that can simultaneously afford momentum-space sensitivity and nanoscale spatial resolution.   In this talk, I will show recent resonant soft X-ray scattering and imaging studies of the spatial textures of electronic orders (charge/spin-density-waves) in cuprate high-Tcs and rare earth nickelate thin films.  For the cuprates, I will present evidence of a doping-induced transition from a 'Wigner glass' to a 'Wigner crystal' state in electron-doped Nd2CuO4, that occurs around the characteristic doping of the Fermi surface reconstruction (~10%). For thin films of rare earth nickelate NdNiO3, I will discuss scanning resonant magnetic nanodiffraction (<100 nm resolution) experiments to elucidate the spatial organization of spin-density-wave domains as a function of temperature across the Neel transition. Intriguingly, we have observed a return-point-memory effect in the spin degrees of freedom and intrinsic scale-invariant textures with power-law correlations that might be suggestive of a second-order nature of the magnetic transition in this material.   I will conclude with some perspectives and a glimpse to very recent resonant coherent diffractive imaging experiments performed at latest-generation, highly-coherent synchrotron X-ray sources to resolve the complex (amplitude/phase) density-wave order parameter down to an ultimate resolution below 30 nm (and beyond).  Event Location: 311 - 2355 East Mall
Event Time: Wednesday, January 16, 2019 | 1:00 pm - 2:00 pm
Event Location:
Henn 309 (NEW LOCATION)
Add to Calendar 2019-01-16T13:00:00 2019-01-16T14:00:00 Partners and Quantum Information Capsules Event Information:  Where do entangled quantum systems store information in a total pure state? This question is nontrivial and interesting since the entanglement among subsystems delocalizes the information, and is significantly related to the information loss problem of evaporating black holes.  So far, a common picture is that of a subsystem and its purification partner sharing the information quantum mechanically. For entangled multiple qubits in an arbitrary pure state, we introduce a new picture of a single qubit in the correlation space referred to as quantum information capsule (QIC), confining the information perfectly.  Unlike the partner picture, in the QIC picture, by swapping the single-body state, leaving other subsystems untouched, the whole information can be retrieved out of the system. After the swapping process, no information remains in the system. Event Location: Henn 309 (NEW LOCATION)
Event Time: Monday, January 14, 2019 | 3:00 pm - 4:00 pm
Event Location:
Hennings 318
Add to Calendar 2019-01-14T15:00:00 2019-01-14T16:00:00 Counting Stars: Developing Probabilistic Cataloguing for Crowded Fields Event Information: The depth of next generation surveys poses a great data analysis challenge: these surveys will suffer from crowding, making their images difficult to deblend and catalogue. Sources in crowded fields are extremely covariant with their neighbours and blending makes even the number of sources ambiguous. Probabilistic cataloguing returns an ensemble of catalogues inferred from the image and can address these difficulties. We present the first optical probabilistic catalogue, cataloguing a crowded Sloan Digital Sky Survey r band image cutout from Messier 2. By comparing to a DAOPHOT catalogue of the same image and a Hubble Space Telescope catalogue of the same region, we show that our catalogue ensemble goes more than a magnitude deeper than DAOPHOT. We also present an algorithm for reducing this catalogue ensemble to a condensed catalogue that is similar to a traditional catalogue, except it explicitly marginalizes over source-source covariances and nuisance parameters. We also detail efforts to make probabilistic cataloguing more computationally efficient and extend it beyond point sources to extended objects. Probabilistic cataloguing takes significant computational resources, but its performance compared to existing software in crowded fields make it a enticing method to pursue further. Event Location: Hennings 318
Event Time: Friday, January 11, 2019 | 10:00 am - 12:00 pm
Event Location:
Room 309, Hennings Building
Add to Calendar 2019-01-11T10:00:00 2019-01-11T12:00:00 Departmental Oral Examination (Thesis Title: “Precise Measurement of Rare Pion Decay”) Event Information: Abstract: A precise measurement of the pion to positron or muon decay branching ratio provides a test of lepton universality incorporated in the Standard Model (SM) of particle physics. If a measurement is consistent with the SM, new constraints could be set on new physics. Most remarkably, a deviation could imply the presence of a new pseudo-scalar interaction whose energy scales up to O(1000 TeV) would enhance the branching ratio by O(0.1%). In some instances, these constraints can far exceed the reach of direct searches at colliders. This dissertation represents the latest experimental measurement effort by the PIENU collaboration. The current analysis presented in this thesis is blinded but includes the highest quality data portion available of around 3M  π → e ν events. Furthermore, major experimental systematic problems have been solved, allowing for increased precision up to 0.12% in the branching ratio and up to 0.06% in test of lepton universality. Event Location: Room 309, Hennings Building
Event Time: Thursday, January 10, 2019 | 4:00 pm - 5:00 pm
Event Location:
Hennings 201
Add to Calendar 2019-01-10T16:00:00 2019-01-10T17:00:00 Towards a more efficient model of particle physics Event Information: Grand unified theories envision the standard model of particle physics as a piece of a larger system.  However, in this talk we will ask the opposite question:  Could the standard model result from a set of algebras much smaller than itself? By the late 1930s, Arthur Conway knew that the complex quaternions (just a 4 complex-dimensional algebra) could single-handedly encode the notion of rotations and boosts, in addition to the degrees of freedom of electric and magnetic fields, energy and momentum, fermionic spin and chirality.  Here we will demonstrate hints that the octonions might be capable of similar feats in efficiency. This colloquium is tailored so as to be as accessible as possible. Students are more than welcome to attend! Event Location: Hennings 201
Event Time: Thursday, January 10, 2019 | 2:00 pm - 3:00 pm
Event Location:
BRIM 311, Stewart Blusson Quantum Matter Institute, 2355 East Mall
Add to Calendar 2019-01-10T14:00:00 2019-01-10T15:00:00 CM Seminar: Materials Informatics: the 4th paradigm Abstract Event Information: Materials informatics (MI) may be considered the 4th paradigm of scientific inquiry, in addition to experimental, theoretical and computational approaches. MI is made possible by the universal access to abundant scientific data, assisted by advances in software and machine learning (ML) to analyze the data. For materials problems with specific designing goals, physics-based indicators (or assumptions) are necessary to help narrowing down the informatics search. In this talk I shall present materials discovery by MI + ML, including 2D ferromagnets, solid state electrolytes, molecules for OLED, and possible high Tc superconductors. We conclude that backed by theory and first principles simulation, and eventually by experimental verification, MI + ML is a very efficient approach for materials discovery. Acknowledgements: work in collaboration with Dr. Eric Zhu (NanoacademicTech., Canada), Dr. Yifa Qin (HZWTECH, Shanghai, China), Dr. Zhongli Liu (McGill), Dr. Xianghua Kong (McGill). Event Location: BRIM 311, Stewart Blusson Quantum Matter Institute, 2355 East Mall
Event Time: Monday, January 7, 2019 | 3:00 pm - 4:00 pm
Event Location:
Hennings 318
Add to Calendar 2019-01-07T15:00:00 2019-01-07T16:00:00 The New Horizons spacecraft's encounter with the small Kuiper Belt object Ultima Thule Event Information: On 1st January 2019 the New Horizons spacecraft encountered a small body beyond Neptune named Ultima Thule. In this informal collquium we will cover the initial results that have emerged this week and provide background on the importance of the science that can be addressed. Event Location: Hennings 318
Event Time: Thursday, December 20, 2018 | 2:00 pm - 3:00 pm
Event Location:
BRIM 311
2355 East Mall
Vancouver BC
V6T 1Z4
Add to Calendar 2018-12-20T14:00:00 2018-12-20T15:00:00 CM Seminar: Cavity Spintronics Event Information: Cavity spintronics (also known as spin cavitronics) is a newly developing, interdisciplinary field that brings together microwave and optical communities with researchers in spintronics and magnetism. The field started around 2014 when it was found that ferromagnets in cavities hybridize with both microwaves and light by light-matter interaction [1]. Since then, the emergence of cavity spintronics has attracted broad interest from groups studying quantum electrodynamics, cavity polaritons, optomechanics, superconductivity, plasmonics, and phononics. At the center stage of the topic is the physics of magnon-photon coupling: Via the quantum physics of spin-photon entanglement on the one hand and classical electrodynamic coupling on the other, magnon-photon coupling connects some of the most exciting concepts in modern physics, such as quantum information and quantum optics, with one of the oldest sciences on earth, magnetism.  This talk aims to provide an introduction to this new frontier of condensed matter physics to researhers working in magnetism, spintronics, quantum information, and microwave technologies. The talk starts with a historical review, tracing this new field back to some of the most courageous work in the history of magnetism, spintronics, cavity quantum electrodynamics,  and polaritons. Recent experiments focusing on the development of new cavity-mediated techniques, such as coupling of magnetic moments, distant manipulation of spin current, qubit-magnon coupling, and conversion between optical and microwave photons, will be highlighted.   [1] Can-Ming Hu, “Dawn of cavity spintronics,” https://arxiv.org/abs/1508.01966 Event Location: BRIM 311 2355 East Mall Vancouver BC V6T 1Z4