Conference

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TQFTs and Topological Phases of Matter

Zhenghan Wang Microsoft Corporation
May 06, 2013

PIRSA:13050022
Mathematical physics
3d boson topological insulators and quantum spin liquids

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics
May 06, 2013

PIRSA:13050021
Condensed Matter
Diluted Magnetism in Iridates: Studies of Rh-doped Sr2Ir2O4

Pat Clancy University of Toronto
April 25, 2013

PIRSA:13040137
Condensed Matter
Higgs Boson in Condensed Matter: From Polaron to Topological Insulator
April 25, 2013

PIRSA:13040132
Particle Physics

Condensed Matter
Tensor Networks: an Overview

Lukasz Cincio Los Alamos National Laboratory
April 25, 2013

PIRSA:13040131
Quantum Information
New Neutron Scattering Results on the Enigmatic Ground State of the Pyrochlore Magnet Tb2Ti2O7

Katharina Fristsch McMaster University
April 25, 2013

PIRSA:13040136
Condensed Matter
Absence of Pauling's Residual Entropy in Dy2Ti2O

Jan Kycia University of Waterloo
April 25, 2013

PIRSA:13040130
Condensed Matter
The Quantum von Neumann Architecture and the Future of Quantum Computing with Superconducting Circuits

Matteo Mariantoni Institute for Quantum Computing (IQC)

April 25, 2013

PIRSA:13040135
Spin-1/2 Heisenberg Antiferromagnet on the Kagome Lattice: a Z2 Spin Liquid with Fermionic Spinons

Zhihao Hao University of Waterloo
April 25, 2013

PIRSA:13040134
Condensed Matter
Reaching Experimentally Quantum Criticality: A Playground to Explore Novel Correlated Quantum States of Matter

Radu Coldea University of Oxford
April 25, 2013

PIRSA:13040133
Condensed Matter
This is What a Scientist Looks Like
- Sampa Bhadra York University
- Natalia Toro Stanford University
- Shohini Ghose Wilfrid Laurier University
March 08, 2013

PIRSA:13030086
The Effects of Limited Resources and Opportunities on Women’s Careers in Physics: Results from the Global Survey of Physicists

Rachel Ivie American Institute of Physics

March 08, 2013

PIRSA:13030082

TQFTs and Topological Phases of Matter

Zhenghan Wang Microsoft Corporation
May 06, 2013

PIRSA:13050022
Mathematical physics
In two spatial dimensions, there is a good correspondence between TQFTs and topological phases of matter for spin systems. I will discuss this correspondence in one and three spatial dimensions for spin systems. If time permits, I will also discuss the situation for fermion systems.
3d boson topological insulators and quantum spin liquids

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics
May 06, 2013

PIRSA:13050021
Condensed Matter
I will discuss recent work on 3d Symmetry Protected Topological (SPT) phases of bosonic systems, and their implications for understanding the more exotic quantum spin liquid phases. First I will describe various characterizations of these 3d SPT phases, in particular their surface effective theories and (when applicable) bulk electromagnetic response. Next I will show how this understanding leads to several new insights into the theory of both 2d and 3d quantum spin liquids. Finally I will provide an explicit construction of several 3d SPT phases in a system of `coupled layers'. This includes a 3d SPT state that is beyond the existing cohomology classification of such states.
Diluted Magnetism in Iridates: Studies of Rh-doped Sr2Ir2O4

Pat Clancy University of Toronto
April 25, 2013

PIRSA:13040137
Condensed Matter
The physics of iridium-based 5d transition metal oxides has attracted significant interest due to the potential for exotic magnetic and electronic ground states driven by strong spin-orbit coupling effects. Among the most extensively studied iridates is the layered perovskite Sr2IrO4, which was recently proposed as the first experimental realization of a novel Jeff=1/2 spin-orbital Mott insulating state. Intriguing similarities between Sr2IrO4 and La2CuO4, the parent compound of the high-Tc cuprates, have also led to speculation that it may be possible to induce superconductivity in this system through chemical doping. We have investigated the magnetic properties of the doped system Sr2Ir1-xRhxO4 using a combination of resonant magnetic x-ray scattering (RMXS), resonant inelastic x-ray scattering (RIXS), and x-ray absorption spectroscopy (XAS) techniques. These measurements reveal the effect of Rh-doping on the magnetic structure, phase diagram, and characteristic magnetic excitations of Sr2IrO4, and provide fundamental information about the role of quenched Rh impurities.
Higgs Boson in Condensed Matter: From Polaron to Topological Insulator
April 25, 2013

PIRSA:13040132
Particle Physics

Condensed Matter
In this talk I will briefly review the polaron physics, which has helped theorists to conceive the BCS theory of conventional superconductors as well as experimentalists to discover high temperature superconductors in the cuprates. Specifically I will talk about how charge carriers obtain their
masses from coupling to the phonon field in one, two, three or higher dimensions. More recently, there is increasing interest in topological insulators where a gap can be opened which may suggest new version of Higgs mechanism in condensed matter.
Tensor Networks: an Overview

Lukasz Cincio Los Alamos National Laboratory
April 25, 2013

PIRSA:13040131
Quantum Information
Tensor network algorithms provide highly competitive tools for analyzing ground state properties of quantum lattice models in one and two spatial dimensions. The most notable examples involve matrix product states, projected entangled pair states and multiscale entanglement renormalization ansatz. The key underlying idea of all the approaches is to decompose a quantum many-body state into a carefully chosen network of tensors.
In this talk I will give an introduction to the subject and show how tensor networks can be used to characterize topological order.
New Neutron Scattering Results on the Enigmatic Ground State of the Pyrochlore Magnet Tb2Ti2O7

Katharina Fristsch McMaster University
April 25, 2013

PIRSA:13040136
Condensed Matter
The ground state of the candidate spin liquid pyrochlore magnet Tb2Ti2O7 (TTO) has been long debated. Despite theoretical expectations of magnetic order below ~1K based on classical Ising-like Tb3+ spins, earlier muSR and neutron scattering experiments showed no long range order down to 50mK. This motivated two theoretical scenarios to account for the apparently disordered ground state: a quantum spin ice scenario and a non-magnetic singlet ground state. I will discuss new neutron scattering measurements on TTO that show short range spin correlations developing below ~ 0.5 K with a (½, ½, ½) ordering wavevector, and a concomitant opening of a spin gap across most of the Brillouin zone. Our measurements also refine the crystal field ground state for Tb3+ in TTO and in its sister, “soft” spin ice compound Tb2Sn2O7.
Absence of Pauling's Residual Entropy in Dy2Ti2O

Jan Kycia University of Waterloo
April 25, 2013

PIRSA:13040130
Condensed Matter
The discovery of the spin-ice phase in Dy2Ti2O7 numbers among the most significant findings in magnetic materials in over a decade. The spin-ice model is based on an elegant analogy to Pauling’s model of geometrical frustration in water ice, and predicts the same residual entropy, as confirmed by numerous measurements. Melko, den Hertog and Gingras, with numerical work using a loop algorithm to speed up equilibration times, were able to determine an ordering for this system. This had not been seen experimentally observed by several groups. I will present new experimental results for the specific heat of Dy2Ti2O7, demonstrating why previous measurements were unable to correctly capture its low temperature behaviour. By carefully tracking the flow of heat into and out of the material, we observe a non-vanishing specific heat at low temperatures indicating the residual entropy does not actually agree with the Pauling value.
The Quantum von Neumann Architecture and the Future of Quantum Computing with Superconducting Circuits

Matteo Mariantoni Institute for Quantum Computing (IQC)

April 25, 2013

PIRSA:13040135

Superconducting quantum circuits have made significant advances over the past decade, allowing more complex and integrated circuits that perform with good fidelity. We have recently implemented a machine comprising seven quantum channels, with three superconducting resonators, two phase qubits, and two zeroing registers. I will explain the design and operation of this machine, first showing how a single microwave photon |1> can be prepared in one resonator and coherently transferred between the three resonators [1]. I will then demonstrate how this machine can be used as the quantum-mechanical analog of the von Neumann computer architecture, which for a classical computer comprises a central processing unit and a memory holding both instructions and data. The quantum version comprises a quantum central processing unit (quCPU) that exchanges data with a quantum random-access memory (quRAM) integrated on one chip, with instructions stored on a classical computer [2]. Finally, I will demonstrate that the quantum von Neumann machine provides one unit cell of a two-dimensional qubit-resonator array that can be used for surface code quantum computing. This will allow the realization of a scalable, fault-tolerant quantum processor with the most forgiving error rates to date [3].
[1] M. Mariantoni et al., Nature Physics 7, 287-293 (2011)
[2] M. Mariantoni et al., Science 334, 61-65 (2011)
[3] A. G. Fowler, M. Mariantoni, J. M. Martinis, and A. N. Cleland, Phys. Rev. A 86, 032324 (2012)
Spin-1/2 Heisenberg Antiferromagnet on the Kagome Lattice: a Z2 Spin Liquid with Fermionic Spinons

Zhihao Hao University of Waterloo
April 25, 2013

PIRSA:13040134
Condensed Matter
Motivated by recent numerical and experimental studies of the spin-1/2 Heisenberg antiferromagnet on kagome, we formulate a many-body model for fermionic spinons, which are just uncoupled spins. The spinons interact with an emergent U(1) gauge field and experience strong short-range attraction in the S=0 channel. The ground state of the model is generically a Z(2) liquid. We calculate the edge of the two-spinon continuum and compare the theory to the slave-fermion approach to the Heisenberg model.
Reaching Experimentally Quantum Criticality: A Playground to Explore Novel Correlated Quantum States of Matter

Radu Coldea University of Oxford
April 25, 2013

PIRSA:13040133
Condensed Matter
Realizing experimentally continuous phase transitions in the electronic ground state of materials near zero temperature as a function of tuning some external parameter (magnetic field, pressure etc.) offers a unique opportunity to probe the extreme regime (near the transition point) where strong quantum correlations encompass the macroscopic sample as a whole, so called “quantum criticality” [1]. In this regime of strong correlations small perturbations/interactions can stabilize novel forms order or collective fluctuations that otherwise do not exist. One of the theoretically most studied paradigms for quantum criticality is a chain of Ising spins driven by a transverse field to a critical point separating spontaneous magnetic order and paramagnetic phases. We have realized this system experimentally by applying strong magnetic fields to the quasi-one-dimensional Ising ferromagnet CoNb2O6 and have probed via single-crystal inelastic neutron scattering the evolution of the magnetic order and spin excitation spectrum as a function of applied field at mili-Kelvin temperatures [2]. Near the critical point the spin excitations were theoretically predicted nearly two decades ago to have a set of quantum resonances (collective modes of vibration of the interacting spins) with universal ratios between their frequencies reflecting an exceptional mathematical structure of the quantum many-body eigenstates with a “hidden” E8 symmetry governing the physics in the scaling limit. Experiments indeed observed evidence for a spectrum of resonances and the ratio between the frequencies of the two lowest modes approached the "golden ratio" near the critical point, as predicted by field theory. As a second example of novel physics near quantum criticality I will discuss how an amplitude-modulated incommensurate spin-density wave (SDW) order appears near the field-induced critical point in the quasi-1D spin-1/2 XY antiferromagnet Cs2CoCl4. Incommensurate SDWs are very uncommon in magnetic insulators and are not stable zero-temperature ground states at the classical mean-field level, we propose that here such a state is stabilized by the strong quantum fluctuations associated with the proximity to the critical point and the weak frustrated inter-chain couplings.
This is What a Scientist Looks Like
- Sampa Bhadra York University
- Natalia Toro Stanford University
- Shohini Ghose Wilfrid Laurier University
March 08, 2013

PIRSA:13030086
The Effects of Limited Resources and Opportunities on Women’s Careers in Physics: Results from the Global Survey of Physicists

Rachel Ivie American Institute of Physics

March 08, 2013

PIRSA:13030082

The results of the Global Survey of Physicists draw attention to the need to focus on factors other than representation when discussing the situation of women in physics. Previous studies of women in physics have mostly focused on the lack of women in the field. This study goes beyond the obvious shortage of women and shows that there are much deeper issues. For the first time, a multinational study was conducted with 15000 respondents from 130 countries, showing that problems for women in physics transcend national borders. Across all countries, women have fewer resources and opportunities and are more affected by cultural expectations concerning child care. We show that limited resources and opportunities hurt career progress, and because women have fewer opportunities and resources, their careers progress more slowly. We also show the disproportionate effects of children on women physicists' careers. Cultural expectations about home and family are difficult to change. However, for women to have successful outcomes and advance in physics, they must have equal access to resources and opportunities. An article based on these findings can be found at: http://www.physicstoday.org/resource/1/phtoad/v65/i2/p47_s1

Title	Speaker(s)	Date	Talk Type	Info link
TQFTs and Topological Phases of Matter	Zhenghan Wang	2013-05-06	Conference	View details
3d boson topological insulators and quantum spin liquids	Senthil Todadri	2013-05-06	Conference	View details
Diluted Magnetism in Iridates: Studies of Rh-doped Sr2Ir2O4	Pat Clancy	2013-04-25	Conference	View details
Higgs Boson in Condensed Matter: From Polaron to Topological Insulator		2013-04-25	Conference	View details
Tensor Networks: an Overview	Lukasz Cincio	2013-04-25	Conference	View details
New Neutron Scattering Results on the Enigmatic Ground State of the Pyrochlore Magnet Tb2Ti2O7	Katharina Fristsch	2013-04-25	Conference	View details
Absence of Pauling's Residual Entropy in Dy2Ti2O	Jan Kycia	2013-04-25	Conference	View details
The Quantum von Neumann Architecture and the Future of Quantum Computing with Superconducting Circuits	Matteo Mariantoni	2013-04-25	Conference	View details
Spin-1/2 Heisenberg Antiferromagnet on the Kagome Lattice: a Z2 Spin Liquid with Fermionic Spinons	Zhihao Hao	2013-04-25	Conference	View details
Reaching Experimentally Quantum Criticality: A Playground to Explore Novel Correlated Quantum States of Matter	Radu Coldea	2013-04-25	Conference	View details
This is What a Scientist Looks Like	Sampa Bhadra, Natalia Toro, Shohini Ghose	2013-03-08	Conference	View details
The Effects of Limited Resources and Opportunities on Women’s Careers in Physics: Results from the Global Survey of Physicists	Rachel Ivie	2013-03-08	Conference	View details

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