Colloquia & Seminars
  • CMTC Seminar
    Speaker Name: Brian Swingle

    Speaker Institution: Stanford

    Title: Renormalization Group Constructions of Topological Quantum Liquids

    Abstract: I will discuss recent work with John McGreevy (1407.8203) on constructing ground state wavefunctions of general gapped Hamiltonians using a renormalization group approach. The formalism provides a number of results including a partial proof of the area law for entanglement entropy, efficient tensor network representations for wavefunctions, a definition of short- and long-range entanglement, and a classification scheme which we conjecture applies to all gapped phases. A special role is played by what we call topological quantum liquids which are gapped phases that are insensitive to the "shape" of space (like quantum Hall fluids).

    Host: Jay D. Sau

    http://www.physics.umd.edu/cmtc/seminars.html
    When: Thu, October 30, 2014 - 11:00am
    Where: 2205 Toll Physics Building
  • Applied Dynamics Seminar
    Speaker Name: Andrey Vilesov

    Speaker Institution : USC, Dept of Chemistry

    Title: X-ray diffraction imaging of quantum vortices in superfluid He droplets
    When: Thu, October 30, 2014 - 12:30pm
    Where: IREAP Large Conference Room, ERF 1207
  • Refreshments for CNAM Cond. Matter Colloquium

    When: Thu, October 30, 2014 - 1:30pm
    Where: physics room 1305F, the "new" Toll Room
  • CNAM Condensed Matter Colloquium
    Speaker Name: Michael Lilly

    Speaker Institution: Sandia National Lab

    Title: Electron spin qubits using donors in silicon

    Abstract: Semiconductor nanoelectronic devices can be combined, or integrated, in a variety of ways to control a single electron and form a qubit. We have focused on silicon devices where the electron is confined on a single donor atom and its spin forms the qubit. Pulsed gate techniques allow spin readout for a single electron. At the end of the readout pulse, the electron is initialized to spin down. We demonstrate spin control by applying pulsed microwaves to coherently rotate the electron spin. Using these techniques, we have measured long spin lifetimes, measured single shot spin readout and recently observed coherent oscillations of a single electron spin. Devices for moving to two-qubits will be discussed at the end of the talk.

    Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
    When: Thu, October 30, 2014 - 2:00pm
    Where: physics room 1201
  • Super-Lie algebra cohomology and de Rham cohomology on supermanifolds
    Speaker: Paul Green
    Abstract: We will try to discuss how one could extend the work of Chavelley-Eilenberg to the case of supermanifolds.
    When: Thu, October 30, 2014 - 3:30pm
    Where: PHY 1117
  • JQI Special Seminar
    Speaker Name: Kartik Srinivasan

    Speaker Institution: NIST

    Title: Quantum frequency conversion and nanocavity optomechanics”.

    Abstract: Quantum frequency conversion is a valuable resource for overcoming spectral mismatch in photonic quantum systems. In this talk, I will provide an overview of our laboratory’s research on a variety of topics related to quantum frequency conversion. This includes proof-of-principle experiments combining single photon sources and established frequency conversion technology, and the development of a number of different nanophotonic devices of relevance to photonic quantum information science. Quantum dot single photon sources, four-wave-mixing-based frequency converters, and nanocavity optomechanical and electromechanical devices are amongst the topics that will be discussed

    Host: Luis Orozco
    When: Mon, November 3, 2014 - 11:00am
    Where: CSS 2400
  • EPT Seminar
    Title: LHC phenomenology of exotic fermions

    Speaker: Tanumoy Mandal, HRI

    Abstract: Many BSM extensions predict the existence of exotic fermions near the
    TeV scale. I will discuss the LHC phenomenology of such heavy exotic
    fermions, namely the vectorlike quarks that arise in various warped
    extra dimensional theories and the color octet electrons which appear
    in some quark-lepton compositeness models. In this regard, I will
    present a generic coupling extraction method with a toy example of
    exotic b' and a generic combined search strategy in the context of
    color octet electron.
    When: Mon, November 3, 2014 - 3:00pm
    Where: PSC 3150
  • Biophysics Seminar
    Speaker Name: Christian Kaiser

    Speaker Institution : John Hopkins University

    Title: Coupling of protein synthesis and folding: Pulling on single nascent chains with optical tweezers

    Abstract : Proteins are synthesized by the ribosome and must generally fold to become functionally active. Nascent protein folding can begin before synthesis is complete, but it has been very difficult to study the mechanisms and consequences of folding on the ribosome. We have developed an experimental system utilizing optical tweezers to follow nascent protein folding, which allows us to observe the folding of single nascent protein molecules in real time. We find that the ribosome slows the formation of stable tertiary interactions and decelerates both folding and misfolding of T4 lysozyme, the model protein used in our initial studies. Our results demonstrate that the ribosome not only decodes the genetic information and synthesizes polypeptides, but also promotes efficient de novo protein folding to the native state. Interestingly, we also found that nascent protein folding can, in turn, regulate ribosome activity. Interactions between the nascent chain and the polypeptide exit tunnel in the ribosome can cause decreased elongation rates and even arrest. We show that nascent chain folding in the vicinity of the ribosomal tunnel exit releases arrest by generating mechanical force. Our results provide mechanistic insight into how nascent chain folding and elongation are coupled during protein synthesis by the ribosome.
    When: Mon, November 3, 2014 - 4:00pm
    Where: 0112 Chemistry Bldg.
  • Space and Cosmic Ray Physics Seminar
    Speaker Name: Daniel Berdichevsky

    Speaker Institution: Goddard Space Flight Center

    Title: On a few properties of very dilute matter frozen in space magnetic fields

    Abstract: For a case study, the flux-rope (FR) that passed Earth on June 2, 2014 (1) (see also listing of magnetic clouds and their properties in the Wind SC MFI science team site at http://wind.gsfc.nasa.gov/mfi/mag_cloud_S1.html), we proceed to interpret plasma and magnetic field observations in the context of MHD. The observations used are 3s average interplanetary magnetic field (Wind/MFI instrument) and 3s plasma (Wind/SWE instruments) data (2). After identifying the observed correlation between electron density, temperature and pressure in the plasma frame of reference we proceed to establish the existence of a relationship between these plasma observables with the magnetic field pressure. By assuming ideal MHD conditions to be valid we proceed to confirm that the medium is diamagnetic, as is to be expected for the MHD state of matter and magnetic field which is assumed to be a superconducting medium. Additionally we infer the presence of magnetization work, as well as a few other constitutive properties of this state of matter.

    (1) Berdichevsky D. B., R. P. Lepping, and C. J. Farrugia, Geometric considerations of the evolution of magnetic flux ropes, Phys. Rev. E67, doi:10.1103/PhysRevE.036405. Lepping R. P. et al, A summary of Wind magnetic clouds for years 1995 – 2003: model-fitted parameters, associated errors and classifications, Ann. Geophysicae, 24, 215-245, 2006.

    (2) Ogilvie, K. W., et al, SWE, A comprehensive plasma instrument for the Wind spacecraft, Space Sci. Rev., 71, 55 – 77, 1995; Lepping R. P., et al , The Wind Magnetic Field Investigation, Space Sci. Rev., 71, 207 – 229, 1995.

    Notes: Coffee, Tea & Cookies 4:15-4:30 PM
    When: Mon, November 3, 2014 - 4:30pm
    Where: CSS Room 2400
  • CMTC Seminar
    Speaker Name: Titus Neupert

    Speaker Institution: Princeton

    Title: Interacting surface states of three-dimensional topological insulators

    Abstract: The surface states of three-dimensional topological insulators are celebrated for their robustness against perturbations, provided that time-reversal symmetry and particle number conservation are not violated. In my talk, I want to survey their possible phases in the limit where interactions between the surface electrons are strong. To that end, I choose a spherical topological insulator geometry to make the surface amenable to numerical studies of finite size systems. In this case, the single-particle problem maps to that of Landau orbitals on the sphere with a magnetic monopole at the center that has unit strength and opposite sign for electrons with opposite spin.

    Restricting the single particle Hilbert space to the small region in the surface Brillouin zone that is covered by the surface Dirac cone enforces a nontrivial quantum geometry on the problem, resulting in distinct real-space localization properties of the electron orbitals. Assuming density-density contact interactions, we find superconducting and anomalous (quantum) Hall phases for attractive and repulsive interactions, respectively. Our setup is ideally adapted to the search for recently proposed topologically ordered surface terminations that could be microscopically stabilized by tailored surface interaction profiles.

    Host: Philip Brydon

    http://www.physics.umd.edu/cmtc/seminars.html
    When: Tue, November 4, 2014 - 11:00am
    Where: 2205 Toll Physics Building
  • Informal Statistical Physics Seminar
    Speaker Name: Mr. Zhiyue Lu

    Speaker Institution : UMCP

    Title : An Integral Method to Compute Helmholtz Free Energies of Crystalline Solids.
    When: Tue, November 4, 2014 - 1:15pm
    Where: 1116 IPST Building, Bldg. 85
  • Physics Colloquium
    Speaker Name: Steven Kivelson

    Speaker Institution: Stanford University

    Title: Quenched Disorder and Vestigial Nematicity

    Abstract: Intermediate phases with “vestigial order” occur when the spontaneously broken symmetries of a “fully ordered” groundstate are restored sequentially as a function of increasingly strong thermal or quantum fluctuations, or of increasing magnitude of quenched randomness. As an important example, incommensurate charge-density-wave short-range order (i.e. with a finite correlation length) and a sharp phase transition to a phase with long-range nematic order is shown to be natural in the presence of weak quenched disorder in systems which, in the absence of disorder, would have unidirectional (stripe) ordered ground states. Recent experiments probing charge order in the pseudo-gap regime of the hole-doped cuprate high-temperature superconductors and nematic order in the Fe based superconductors are interpreted in light of these results.
    When: Tue, November 4, 2014 - 4:00pm
    Where: PSC Lobby
  • CMTC Seminar
    Speaker Name: Steven Kivelson (Stanford)

    Title: Theory of Intertwined Orders in High Temperature Superconductors

    Abstract: The electronic phase diagrams of many highly correlated systems, and in particular the cuprate high temperature superconductors, are complex, with many different phases appearing with similar - sometimes identical - ordering temperatures even as material properties, such as a dopant concentration, are varied over wide ranges. This complexity is sometimes referred to as "competing orders." However, since the relation is intimate, and can even lead to the existence of new phases of matter such as the putative "pair-density-wave," the general relation is better thought of in terms of "intertwined orders." We selectively analyze some of the experiments in the cuprates which suggest that essential aspects of the physics are reflected in the intertwining of multiple orders-not just in the nature of each order by itself. We also summarize and critique several theoretical ideas concerning the origin and implications of this complexity.

    Host: Jay D. Sau

    http://www.physics.umd.edu/cmtc/seminars.html
    When: Wed, November 5, 2014 - 10:00am
    Where: 2205 Toll Physics Building
  • Nuclear Physics Seminar
    Title: Massive and massless modes of the triplet phase of neutron matter

    Speaker: Srimoyee Sen, UMD

    Abstract: Neutron matter at densities of the order of the nuclear saturation density is believed to have neutrons paired in the 3P2 channel. We study the low lying modes of this phase and find two massless modes (angulons), resulting from the spontaneous breaking of rotational symmetry as well as three other, gapped modes. We compute their masses at arbitrary temperatures. We also estimate the neutrino emissivity of the goldstone modes in the presence of a magnetic field.
    When: Wed, November 5, 2014 - 1:00pm
    Where: PSC 3150
  • Fall CMTC Symposium -- Day 1
    Talk schedule:

    11:00 AM Pallab Goswami, Axial anomaly and negative longitudinal magnetoresistance: theory vs. experiment

    11:45 AM Alejandro Lobos, Magnetic edge-states in strongly interacting one-dimensional topological Kondo insulators

    1:30 PM Jed Pixley, Unconventional Superconductivity near a Kondo Destroyed Quantum Critical Point

    2:15 PM Jimmy Williams, Quantum Nanoelectronics in Oxides

    3:00 PM Vlad Manucharyan, Single Cooper pair proximity effect in mesoscopic quantum dots

    The entire talk schedule can be found at http://www.physics.umd.edu/cmtc/seminars.html
    When: Wed, November 5, 2014 - 11:00am
    Where: PHY 2205
  • Fall CMTC Symposium -- Day 2
    Talk schedule:

    11:00 AM William Cole, Magnetism and superfluidity of spin-orbit coupled bosons in one dimension

    11:45 AM Xiaopeng Li, Chiral spin superfluidity and spontaneous spin Hall effect in optical lattices

    1:30 PM Stefan Natu, What can we learn from far from equilibrium dynamics in interacting Bose gases?

    2:15 PM Juraj Radic, Stoner ferromagnetism in a thermal pseudospin-1/2 Bose gas

    3:00 PM Setiawan, Topological Phase Transition in Spin Orbit-Coupled Ultracold Fermi Gas

    The entire talk schedule can be found at http://www.physics.umd.edu/cmtc/seminars.html
    When: Fri, November 7, 2014 - 11:00am
    Where: PHY 2205
  • JQI Seminar
    Speaker Name: Alan Aspuru-Guzik

    Speaker Institution: Harvard

    Hosts: Luis Orozco, James Williams

    Title and Abstract to follow
    When: Mon, November 10, 2014 - 11:00am
    Where: CSS 2400
  • EPT Seminar
    Title: tk

    Speaker: Michael Graesser, Los Alamos National Laboratory

    Abstract: tk
    When: Mon, November 10, 2014 - 3:00pm
    Where: PSC 3150
  • Space and Cosmic Ray Physics Seminar
    Speaker Name: Marc Swisdak

    Speaker Institution : University of Maryland

    Title: TBA

    Abstract: TBA

    Notes: Coffee, Tea & Cookies 4:15-4:30 PM
    When: Mon, November 10, 2014 - 4:30pm
    Where: CSS Room 2400
  • CMTC Seminar
    Speaker Name: Konstantin Matveev

    Speaker Institution: Argonne National Laboratory

    Title: Conductance of uniform quantum wires

    Abstract: At low temperatures the conductance of a single channel quantum wire takes the quantized value e^2/h, a universal combination of the electron charge and Planck's constant. This result is well understood in the model of noninteracting electrons. I will discuss corrections to the conductance of long uniform quantum wires caused by interactions between electrons. Properties of such one-dimensional systems are commonly described in terms of the Luttinger liquid theory. In this approximation, the excitations of the system are noninteracting bosons decoupled from the electric current flowing through the wire, and the conductance remains quantized. I will show that relaxation processes not captured by the Luttinger liquid theory lead to equilibration of the excitations with the current and give rise to a temperature-dependent correction to the conductance. The latter is determined by the velocity of the excitations and the relaxation rate.

    Host: Jay D. Sau

    http://www.physics.umd.edu/cmtc/seminars.html
    When: Tue, November 11, 2014 - 11:00am
    Where: 2205 Toll Physics Building
 

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