Past Events

  • Condensed Matter seminar: "Quantum Many-Body Physics Beyond Ground States"

    David Rittenhouse Laboratory, A4

    Thomas Iadecola, University of Maryland

    Recently a set of traditional assumptions in quantum condensed matter theory has been upended by the realization that many-body systems can host stable quantum phenomena at infinite temperature.  I will discuss recent work suggesting that there is a much richer landscape of such phenomena than has so far been appreciated.  First, I will show how strongly disordered quantum many-body systems can spontaneously segregate into delocalized and localized degrees of freedom, leading to a so-called "mobility emulsion." Second, I will discuss how symmetries in otherwise generic sys

  • Condensed Matter seminar: "Excitons in Flatland: Exploring and Manipulating Many-body Effects on the Optical Excitations in Quasi-2D Materials"

    David Rittenhouse Laboratory, A4

    Diana Qiu, Lawrence Berkeley Laboratory

    Since the isolation of graphene in 2004, atomically-thin quasi-two-dimensional (quasi-2D) materials have proven to be an exciting platform for both applications in novel devices and exploring fundamental phenomena arising in low dimensions. This interesting low-dimensional behavior is a consequence of the combined effects of quantum confinement and stronger electron-electron correlations due to reduced screening.

  • Condensed Matter seminar: "Strange quantum matter: Fermi surfaces sans Fermi liquids"

    David Rittenhouse Laboratory, A4

    Debanjan Chowdhury, Massachusetts Institute of Technology

    The concept of electronic quasiparticles, as introduced by Landau, is one of the cornerstones of the theory of quantum many-body systems. However, a growing number of recent experiments in strongly correlated quantum materials have forced us to confront the existence of quantum matter for which the concept of electronic quasiparticles does not apply. In the first part of this talk, I will consider the physics of an electrical insulator, where recent experiments have suggested the existence of gapless neutral fermionic excitations.

  • Condensed Matter seminar: "Exploring the Landscape of Complex Quantum States: From New Phases of Matter to Robust Schemes for Quantum Computation"

    David Rittenhouse Laboratory, A4

    Ksheerasagar "Sagar" Vijay, Harvard University

    We present recent advances in our understanding of (i) exotic quantum phases of matter in three dimensions, and (ii) robust mechanisms for storing and processing quantum information, that have been enabled by new techniques to study highly-entangled quantum states.  First, we introduce fundamentally new kinds of gapped quantum phases in three spatial dimensions, which are characterized by the presence of point-like excitations that are strictly immobile at zero temperature, and by degenerate ground-states that are locally indistinguishable.

  • Condensed Matter seminar: "Tensor Gauge Theories of Fractons"

    David Rittenhouse Laboratory, A4

    Michael Pretko, University of Colorado

    A fracton is an unusual new type of emergent quasiparticle, first proposed in the context of quantum spin liquids, which does not have the ability to move by itself.  Rather, fractons can only move by forming certain bound states.  In this talk, I will show that symmetric tensor gauge theories provide a natural theoretical framework for fractons, with the unusual mobility restrictions encoded in a set of higher moment charge conservation laws, such as conservation of dipole moment.  I will then show how the tensor gauge theory formalism identifies the conventional ela

  • Condensed Matter seminar: "The Berry curvature dipole of metals and the crossover from composite fermions to exciton superfluid”

    David Rittenhouse Laboratory, A4

    Inti Sodemann-Villadiego, Max Planck Institute, Dresden

    The first part of this talk will summarise our progress in non-linear transport of metals. I will describe a non-linear Hall effect that is allowed by time reversal symmetry and is controlled by the "Berry curvature dipole” (the average of the Berry curvature gradient in momentum space). I will argue that such Berry curvature dipole offers a solution to the old problem of defining an “order parameter” for broken inversion symmetry in metals, by playing the role of a non-linear version of the Drude weight.

  • Condensed Matter seminar: "Dirty Quantum Magnets"

    David Rittenhouse Laboratory, A4

    Itamar Kimchi, University of Colorado

    Studying quantum entanglement over the past 1--2 decades has allowed us to make remarkable theoretical progress in understanding correlated many-body quantum systems. However electrons in real materials experience random heterogeneities ("dirt") whose theoretical treatment, including strong correlations, has been a challenge.

  • Condensed Matter Seminar: "Revisiting and Repurposing the Double Helix"

    David Rittenhouse Laboratory, A6

    Taekjip Ha, Johns Hopkins University

    DNA is an iconic molecule that forms a double helical structure, providing the basis for genetic inheritance, and its physical properties have been studied for decades. In this talk, I will present evidence that sequence and methylation dependent physical properties of DNA such as flexibility and self-association may be important for biological functions [1, 2]. In addition, I will present a new application of DNA where mechanical modulations of cell behavior can be studied at the single molecule level using rupturable DNA tethers [3].

  • Condensed Matter Seminar: "Soft complexity in gels: network connectivity, viscoelasticity and failure"

    David Rittenhouse Laboratory, A6

    Emanuela Del Gado, Georgetown University

    Soft matter (colloids, polymers, proteins…) often self-assembles into gels with diverse structure and mechanics, ubiquitous in nature and extensively used to improve diverse industrial products, where they provide texture, softness, and stability. Through the interplay between their microstructure with an imposed deformation, they can be stretched, flow, squeezed or fractured, but controlling and being able to design such processes (think for example to soft inks for 3D printing technologies) requires a fundamental understanding that is still lacking.

  • Condensed Matter Seminar: "Terahertz-frequency light fields driving quantum material electrons, ions, and spins"

    David Rittenhouse Laboratory, A6

    Keith Nelson, Massachusetts Institute of Technology

    Terahertz-frequency light pulses can now be generated routinely with field amplitudes sufficient to drive highly nonlinear responses of materials and molecules.