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Cornell University
LASSP -  Laboratory of Atomic and Solid State Physics

Cornell Laboratory for Atomic and Solid State Physics

Christopher L. Henley Symposium

Christopher L. Henley
Prof Christopher L. Henley

59th Birthday Celebration
& Symposium

Join  with Professor Christopher L. Henley, friends and colleagues as we celebrate the contributions of Prof. Henley to the field of theoretical solid state physics. Our international panel of speakers will cover topics inspired by Henley's work in biophysics, quasicrystals, frustration, and interacting electrons and numerical methods.

Friday September 12, 2014

8:30AM–5:00PM, Banquet at 6:00PM

401 Physical Sciences Building

Cornell University

Register

Registration is closed as of September 4, 2014. Interested attendees should email je277@cornell.edu for availability.

Meals provided for out-of-town guests.

Cornell employees will be charged for cost of meals.

$32 for the Symposium

$63 for Symposium & Banquet

$31 for the Banquet only

Travel

Lodging links:

We recommend flying into the Ithaca Airport for convenience.

If you fly to Syracuse Airport, Ithaca Airline Limosine has a round trip service for $130.

Please contact Douglas Milton (dem8@cornell.edu) for any specific travel questions.

Organizers

  • Eun-Ah Kim, Cornell University
  • Veit Elser, Cornell University
  • Jane Kondev, Brandeis University

Program [PDF]

8:30 Arrival

8:50 Opening Remarks
Veit Elser, Cornell University

Frustration
Chair Veit Elser, Cornell University

9:00 Michel Gingras, University of Waterloo and Canadian Institute for Advanced Research
Has Compelling Experimental Evidence for Order-by-Disorder at Last Been Found in a Frustrated Magnetic Material?

Has Compelling Experimental Evidence for Order-by-Disorder at Last Been Found in a Frustrated Magnetic Material?

Michel Gingras, University of Waterloo and Canadian Institute for Advanced Research

Abstract: In some magnetic systems, known as frustrated magnets, the lattice geometry or the competition between different spin-spin interactions can lead to a sub-exponentially large number of accidentally degenerate classical ground states. Order-by-disorder (ObD) is a concept of central importance in the field of frustrated magnetism and to which Chris Henley made significant contributions in the late 1980s and early 1990s.

Saddled with large accidental degeneracies, a subset of states, those that support the largest quantum and/or thermal fluctuations, may be selected to form true long-range order. ObD has been discussed extensively on the theoretical front for over 30 years and proposed to be at play in a number of experimental settings.

Unfortunately, convincing demonstrations of ObD in real materials have remained scarce. In this talk, I will review the phenomena of thermal and quantum of order-by-disorder, mention the singular contributions Chris made to our understanding of ObD and, finally, discuss how recent work may have evinced compelling evidence for ObD in some frustrated XY pyrochlore antiferromagnetic materials.

9:30 Collin Broholm, The Johns Hopkins University
Neutron Scattering from Corner-sharing Simplexes - slides [PDF]

Neutron Scattering from Corner-sharing Simplexes

Collin Broholm, The Johns Hopkins University

10:00 David Huse, Princeton University
Order by disorder in spin glasses - slides [PDF]

Order by disorder in spin glasses

David Huse, Princeton University

slides [PDF]

slides [PDF]

Abstract: The phenomenon of "order by disorder" occurs in systems with highly degenerate ground states, when among the ground states those that are ordered have higher entropy than those that are disordered. Chris Henley made many important contributions to this subject for geometrically frustrated magnets. A similar story happens for +/-J Ising spin glasses, as has been realized only rather recently. I will discuss our results for the two-dimensional case (Thomas, Huse and Middleton, PRL 107, 047203 (2011)).

10:30 Break

 

Quasicrystals
Chair Mike Widom, Carnegie Mellon University

11:00 Marc de Boissieu,Université de Grenoble, Science et Ingénierie des Matériaux et Procédés
Quasicrystals: structure and dynamics - slides [PDF]

Quasicrystals: structure and dynamics

Marc de Boissieu,Université de Grenoble, Science et Ingénierie des Matériaux et Procédés

slides [PDF]

Abstract: The discovery of quasicrystals in 1982 by Dan Shechtman, has been a breakthrough in crystallography which led to a paradigm shift and has deeply modified our understanding of long range ordered materials. Indeed, quasicrystals are materials which are long range ordered but without periodicity: their diffraction pattern presents sharp Bragg peaks but with symmetries, such as five-fold rotation axes, incompatible with lattice translation. After an introduction on quasicrystals, recent results on their atomic structure in the binary icosahedral CdYb quasicrystal system will be presented. The structure of the quasicrystal is now well understood, and atomic scale simulations are at hand.

References
1. T. Janssen, G. Chapuis and M. de Boissieu: Aperiodic Crystals. From modulated phases to quasicrystals, Oxford University Press, Oxford 2007
2. Takakura H, Gomez C P, Yamamoto A, de Boissieu M and Tsai A P 2007 Nature Materials 6 58.
3. M. de Boissieu, S. Francoual, M. Mihalkovic, K. Shibata, et al. Nature Materials, 6, 977-984, (2007).
4. H. Euchner, T. Yamada, H. Schober, S. Rols, M. Mihalkovic, et al. J. Phys.: Condens. Matter, 24, 415403, (2012).
5. H. Euchner, T. Yamada, S. Rols, T. Ishimasa, Y. Kaneko, J. Ollivier, H. Schober et al. J. Phys.: Condens. Matter, 25, 115405, (2013)
6. T. Yamada, H. Euchner, C. P. Gómez, H. Takakura, R. Tamura and M. de Boissieu J. Phys.: Condens. Matter, 25, 205405, (2013).

11:30 Marek Mihalkovic, Slovak Academy of Science
Canonical-cell tiling and real icosahedral structures

Canonical-cell tiling and real icosahedral structures

Marek Mihalkovic, Slovak Academy of Science

12:00 Ron Lifshitz, Tel Aviv University
Mesoscopic Quasicrystals

Mesoscopic Quasicrystals

Ron Lifshitz, Raymond & Beverly Sackler School of Physics & Astronomy, Tel Aviv University

Abstract: Most of the research on quasicrystals, since their discovery over three decades ago, has concentrated on the study of solid-state quasicrystals in the form of inter-metallic alloys. In my talk I shall focus on quasicrystals composed of building blocks whose dimensions are on a mesoscopic scale of tens to thousands of nanometers. These range from artificially constructed metamaterials, such as photonic quasicrystals, to self-assembled soft-matter quasicrystals[1-3]. In addition to having promising applications, especially in the optical domain, these materials give us the opportunity to study quasicrystals in ways that were impossible before. As time permits, I shall discuss a few aspects of our work on these systems, ranging from our recent explanation of the stability of certain quasicrystals composed of soft isotropic particles [4,5], and our numerical discovery of "cluster quasicrystals" [6], to the design of nonlinear photonic quasicrystals for optical frequency conversion [7].

[1] Zeng, Ungar, Liu, Percec, Dulcey, & Hobbs (2004)Nature 428, 157. [2] Hayashida, Dotera, Takano, & Matsushita (2007) Phys. Rev. Lett. 98, 195502. [3] Talapin, Shevchenko, Bodnarchuk, Ye, & Murray (2009) Nature 461, 964. [4] Lifshitz & Diamant (2007) Phil. Mag. 87, 3021. [5] Barkan, Diamant, & Lifshitz (2011)  Phys. Rev. B 83, 172201. [6] Barkan, Engel, & Lifshitz (2014) Phys. Rev. Lett. 113, in press. [7] Lifshitz, Arie, & Bahabad (2005) Phys. Rev. Lett. 95, 133901.

 

12:30 Lunch

 

Interacting electrons and numerical methods
Chair Jan von Delft, University of Munich

1:30 Bert Halperin, Harvard University
Fractional quantized Hall effect and phase transitions in the lowest Landau level of monolayer graphene

Fractional quantized Hall effect and phase transitions in the lowest Landau level of monolayer graphene.

Bertrand I. Halperin, Harvard University
Many fractional quantized Hall states have been seen in the zeroth Landau level of graphene (i.e., in the range -2 < ν < 2), but there are striking differences between the wings of the Landau level (|ν | > 1) and the center portion (|ν | < 1). In the outer portion, fractions with odd numerator seem to be missing. In the inner portion, fractions with even and odd numerators are seen, and experiments at Harvard also see phase transitions, as a function of magnetic field or electron density, at fixed filling fraction. We argue that these differences can be largely understood as a consequence of the effects of interaction terms in the Hamiltonian that violate SU(2) valley symmetry, which act differently in the wings and in the center of the Landau level. Missing fractions may be a consequence of low-energy Skyrmions.

2:00 Siew-Ann Cheong, Nanyang Technological University
Numerical Methods as Exploration Tools for Theoretical Condensed Matter Physics - slides [PPTX]

2:30 Hitesh Changlani, University of Illinois at Urbana-Champaign
Density matrix based numerical method for discovering order in interacting systems

Density matrix based numerical method for discovering order in interacting systems

Hitesh Changlani, University of Illinois at Urbana-Champaign

Abstract: As part of my graduate research with Professor Chris Henley, I ventured into understanding the low energy physics of randomly diluted antiferromagnets at the percolation threshold [1]. In this talk I will summarize the key ideas we developed during this work to provide a context for the general themes that emerged from this study. In particular, I will show how one can process numerical information from low-lying "quasidegenerate states" (QD) in a manner that reveals the underlying low energy degrees of freedom. This is done with a quasidegenerate density matrix (QDDM), a mathematical construct involving diagonal and off-diagonal density matrices (those between all pairs of QD states). I will conclude by providing representative examples, in which numerical data from accurate many-body calculations was used to reveal the underlying order parameter and to detect a quantum phase transition [2].

[1] H.J. Changlani, S. Ghosh, S. Pujari, C.L. Henley, Phys. Rev. Lett. 111, 157201 (2013)
[2] C.L. Henley and H.J. Changlani, arXiv: 1407.4189

3:00 Anders W Sandvik, Boston University
Low-energy excitations in percolating quantum spins - slides [PDF]

Low-energy excitations in percolating quantum spins

Anders W Sandvik, Boston University

slides [PDF]

Abstract: When the 2D square-lattice S=1/2 Heisenberg antiferromagnet is randomly diluted with non-magnetic impurities, the long-range order is lost only at the classical percolation point. The percolating cluster possesses long-range order although it has vanishing stiffness, as is the case also in the corresponding classical system. However, the excitations of the quantum system have distinct non-classical features, due to the formation of almost localized moments in regions of the cluster where there is sublattice imbalance (excess of sites belonging to one of the sublattices). These excitations were discovered and detected using exact diagonalization of small clusters as well as quantum Monte Carlo simulations of larger systems. I will discuss some aspects of this work.

 

3:30 Break

 

Biological physics
Chair: Chen Zeng, George Washington University

4:00 Jane Kondev, HHMI and Brandeis University
DNA folding in cells

DNA folding in cells

Jane Kondev, HHMI and Brandeis University

Abstract: The length of DNA in a living cell exceeds the linear size of the volume it occupies by three or more orders of magnitude. Therefore, for DNA to fit inside a cell it must be folded up. Experimental techniques based on fluorescence imaging and DNA sequencing have begun to quantitatively characterize the folded state of DNA in cells, revealing mathematical rules that can be understood in the context of simple physics models. In this talk I will describe the emerging experimental and theoretical landscape of DNA folding in cells, and discuss how cells might control the folded state of DNA so as to regulate its biological functions such as recombination and transcription.

4:30 Rob Phillips, California Institute of Technology
How Viruses Make New Viruses: A Single-Molecule View

How Viruses Make New Viruses: A Single-Molecule View

Rob Phillips, California Institute of Technology

Abstract: One of the most beautiful and interesting meeting places of geometry, biology and physics is the study of viruses. Using single-molecule techniques, it has become possible to examine viruses both while they package and eject their DNA. This talk will begin with simple physical arguments about the forces that attend viral DNA packaging and ejection as well as the resulting time scales for such ejection. Using these predictions as motivation, I will describe single-molecule experiments designed to watch the ejection process one virus at a time both in vitro and in vivo. In both settings, the results provide challenges to current theoretical interpretations of the ejection process and build upon many of the scientific themes that have been central to the career of Prof. Chris Henley.

5:00 Robijn Bruinsma, University of California at Los Angleles
DNA confinement drives uncoating of the HIV Virus - slides [PDF]

DNA confinement drives uncoating of the HIV Virus

I. Rouzina1 and R. Bruinsma2
1 Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN
2 Department of Physics and Astronomy; Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA

slides [PDF]

Abstract: The capsid that protects the genome molecule(s) of a virus is in general quite robust against mechanical stress. An outstanding exception is the mature capsid of retroviruses, such as HIV. We present a description of the mature HIV capsid where a key function is not the mechanical protection of the genome but instead a role as a "reactor vessel" for the action of the enzyme reverse transcriptase that converts single-stranded RNA molecules into double-stranded DNA molecules inside mature HIV viral capids. The uncoating of the HIV virus is determined by the fracture force exerted on the capsid wall by the DNA torus that is produced by the reverse transcriptase.

 

 

6:00 Banquet

 

Attendees

Vinay Ambegaokar, Cornell University
Neil & Judith Ashcroft, Cornell University
Collin Broholm, The Johns Hopkins University
Robijn Bruinsma, University of California at Los Angleles
Susan  Buck-Morris, Cornell University
Ernest Chan, EXP Capital Management, LLC.
Hitesh & Suravi Changlani, University of Illinois at Urbabna-Champaign
Hanrong Chen, Harvard University
Siew-Ann Cheong, Nanyang Technological University
Eugene Chudnovsky, Lehman College
Eric Cockayne, Ceramics Division, NIST
Itai Cohen, Cornell University
Marc de Boissieu, Science et Ingénierie des MAtériaux et Procédés
Carol  Devine, Cornell University
Veit & Liz Elser, Cornell University
Carl & Zsofia Franck, Cornell University
Michel Gingras, University of Waterloo
Lis Gronlund, Union of Concerned Scienctists
Nan Gu, Massachusetts Institute of Technology
Bert Halperin, Harvard University
Lorien Hayden, Cornell University
Christopher Henley, Cornell University
Nancy M. Henley
Richard Hennig, Cornell University
Paul A. Houle
David Huse, Princeton University
Eun-Ah Kim, Cornell University
Christopher King
Genya Kolomeisky, University of Virginia
Eugene Kolomiesky, Academy of Sciences of the USSR
Jane Kondev, Brandeis University
Matt Lapa, Univ. Illinois at Urbana-Champaign
Andreas Lauchli, University of Innsbruck
Michael Lawler, Cornell University
Seung-Hun  Lee, University of Virginia
Pak-Wo Leung, Hong Kong University of Science and Technology
Ron Lifshitz, Tel Aviv University
Christos Likos, University of Vienna
See Joon Lim, Stanford University
N. David Mermin, Cornell University
Alan Middleton, Syracuse University
Marek Mihalkovic, Slovak Academy of Science
Erich Mueller, Cornell University
Chris Myers, Cornell University
Mark Newman, University of Michigan
Jeevak Parpia, Cornell University
Abhay  Pasupathy, Columbia University
Ritchie Patterson, Cornell University
Rob Phillips, California Institute of Technology
Sumiran Pujari, Kentucky University
Raghu Raghavan, Act-On Software, Inc.
Ramakrishna Raghavan, NYC
Jacob Ruff, Cornell University
Anders Sandvik, Boston University
Jim Sethna, Cornell University
Qing Shen, Cornell University
Eric  Siggia, Cornell University
Sophia Robin Sklan, MIT
Arthur Smith, American Physical Society
Bhuvanesh Sundar, Cornell University
Oleg Tchernyshyov, Johns Hopkins University
Petros Thomas, Cornell University
Robert Thorne, Cornell University
Cyrus Umrigar, Cornell University
Abolhassan Vaezi, Cornell University
Ben Villalobos
Mike & Mary Widom, Carnegie Mellon University
Chen Zeng, George Washington University
Nai- Gong Zhang, The George Washington University