Since 2002 Perimeter Institute has been recording seminars, conference talks, and public outreach events using video cameras installed in our lecture theatres. Perimeter now has 7 formal presentation spaces for its many scientific conferences, seminars, workshops and educational outreach activities, all with advanced audio-visual technical capabilities. Recordings of events in these areas are all available On-Demand from this Video Library and on Perimeter Institute Recorded Seminar Archive (PIRSA). PIRSA is a permanent, free, searchable, and citable archive of recorded seminars from relevant bodies in physics. This resource has been partially modelled after Cornell University's arXiv.org.
We introduce a new classical spin liquid on the pyrochlore lattice by extending spin ice with further neighbour interactions. This disorder-free spin model exhibits a form of dynamical heterogeneity with extremely slow relaxation for some spins while others fluctuate quickly down to zero temperature. We thus call this state "spin slush", in analogy to the heterogeneous mixture of solid and liquid water.
In this talk, I will describe a new technique—stochastic resonance magnetic force microscopy (SRMFM)—developed in my group for imaging the vortex dynamics in multiply connected superconducting devices. Unlike existing techniques, which directly image vortices, our technique relies on the mechanism of stochastic resonance to image the fluctuations between different vortex configurations.
General relativity is invariant under diffeomorphisms, and
excitations of the metric corresponding to diffeomorphisms
are nonphysical. In the presence of a boundary, though --
including a boundary at infinity -- the Einstein-Hilbert
action with suitable boundary terms is no longer fully
invariant, and certain diffeomorphisms are promoted to
physical degrees of freedom. After briefly describing how
this happens in (2+1)-dimensional AdS gravity, I will
report on work in progress on the asymptotically flat case,
The kagome lattice in a mineral compound "Herbertsmithite" represents structurally the most ideal kagome Heisenberg antiferromagnet known to date. Herbertsmithite does not undergo a magnetic long-range order or spin freezing at least down to ~J/2000. We will present 17-Oxygen and 2-Deuterium single crystal NMR study of Herbertsmithite. We will demonstrate that the ground state of the kagome plane has a spin gap ~ 0.05J [1], and ~5% excess Cu2+ ions occupying the out-of-plane Zn2+ sites are the only defects [2].
A many-body quantum system on the verge of instability between competing ground states exhibits emergent phenomena. Interacting electrons on triangular lattices are likely subjected to multiple instabilities in the charge and spin degrees of freedom, affording diverse phenomena related to the Mott physics. The molecular conductors are superior model systems for studying the Mott physics because of the designability and controllability of material parameters such as lattice geometry and bandwidth by chemical substitution and/or pressure.
Current observations provide precise but limited information about inflation and reheating. Theoretical considerations, however, suggest that the early universe might be filled with a large number of interacting fields with unknown interactions. How can we quantitatively understand the dynamics of perturbations during inflation and reheating in such scenarios and when only limited
constraints are available from observations? Based on a precise
In recent years, there has been much interest in honeycomb lattice quantum magnets described by Kitaev-Heisenberg Hamiltonian. For example, honeycomb lattice iridates, such as Na2IrO3 and Li2IrO3 have been intensely scrutinized. Recently, we proposed that a 4d honeycomb magnet α-RuCl3 is a promising candidate material in which Kitaev physics could be studied. I will give an overview of the physics of alpha-RuCl3, and talk about recent experimental and theoretical advances.
Spectral distortions of the CMB provide a powerful new probe of early Universe processes. Even if so far no average spectral distortion has been seen, LCDM does predict several signals that are within reach of current technology. In this talk, I will give a broad brush overview of our most recent understanding of the formation and evolution of distortions in the early Universe, highlighting guaranteed LCDM signals and what we hope to learn from them about the Universe we live in.
We have recently demonstrated an experimental platform to isolate 2D materials that are unstable in the ambient environment. I will discuss our recent studies of the charge density wave compound 1T-TaS2 and superconducting 2H-NbSe¬ in the atomically thin limit, made possible using this technique. In TaS2, we uncover a new surface charge density wave transition that is distinct from that in the bulk layers, as well as demonstrate continuous electrical control over this phase transition.
Beyond their deceptively featureless ground states, spin liquids are particularly remarkable in the exotic nature of their (fractionalised and gauge charged) excitations. Quenched disorder can be instrumental in nucleating or localising defects with unusual properties, revealing otherwise hidden features of these topological many-body states. This talk discusses how to turn the nuisance of disorder into a powerful probe and origin of new collective behaviour.