Gotham-Metro Condensed Matter Meeting (1)

Gotham-Metro Condensed Matter Meeting

Friday, November 12, 2010

The New York Academy of Sciences

Presented By

 

From Richard Feynman to J. Robert Oppenheimer; from Thomas Edison to Nikola Tesla; from Egon Spengler to Reed Richards; the city of New York has served as a birthplace, workshop, and fictional setting for some of the most renowned physical scientists of the past century. To carry on the city’s reputation for fostering and connecting top scientific minds, students and faculty from over a dozen institutions in the New York metropolitan area have come together to organize a day-long science session bringing together the best in local condensed matter physics; the Gotham-Metro Condensed Matter Meeting! Hosted by the New York Academy of Sciences, this biannual conference is a fantastic chance for faculty, postdocs, and students to share ideas and research with fellow physicists training and working within commuting distance of New York City. The conference will include keynote lectures by distinguished speakers in both hard and soft condensed matter physics, student talks highlighting current research, poster sessions presenting research projects from diverse subfields, and a debate panel of local physicists discussing the most important unanswered questions in condensed matter physics, as well as a catered breakfast, lunch and reception. With some of the best new research in the Northeast, a fantastic view of Manhattan, and so many opportunities for new ideas and collaborations, this is an event no self-respecting physicist should miss!

Scientific Organizing Committee

Darya Aleinikava

College of Staten Island

Yang Bo

Princeton University

Sara Callori

Stony Brook University

Mauricio Campuzano

Stevens Institute of Technology

Eugene Dedits

College of Staten Island

Lisa Dixon

New York University

Dmitri Efetov

Columbia University

Senia Katalinic

Rutgers University

Manas Kulkarni

Stony Brook University

Jian Li

City College of New York

Matt Lohr

University of Pennsylvania

Peter Orth

Yale University

Anil Shrirao

New Jersey Institute of Technology

Chuck-Hou Yee

Rutgers University

Ye Xu

Yale University

Zhonghua (Lukas) Zhao

City College of New York

Past Meetings

Gotham-Metro Condensed Matter Meeting Spring 2009
Gotham-Metro Condensed Matter Meeting Fall 2009
Gotham-Metro Condensed Matter Meeting Spring 2010

Agenda

*Presentation times are subject to change.


9:00 AM

Poster Set-Up and Breakfast

10:00 AM

Soft Condensed Matter Keynote Presentation

When and How To Walk on Water: A New Perspective on Shear Thickening in Suspensions
Heinrich Jaeger, University of Chicago

SESSION I Short Talks

11:00 AM

Randomly packing spheres
Yuliang Jin, City College of New York

Quasiparticle scattering from vortices in d-wave superconductors:
Superflow and Berry phase contributions

Sriram Ganeshan, SUNY Stony Brook

SESSION II Short Talks

12:00 PM

Electron transport in graphene on Boron N itride
Cory Dean, Columbia

Separating stretching from folding in fluid mixing
Douglas H. Kelley, Yale University

Dynamical Mean-Field Theory for Quantum Chemistry
Nan Lin, Columbia University

Rapid prototyping method for cell patterning:
Adhesive tape master and its soft lithographic replication to pattern the MVEC cell

Anil Shrirao, NJ Institute of Technology

1:00 PM

Lunch (Provided)

2:00 PM

Hard Condensed Matter Keynote Presentation

Computational Design of New Multifunctional Materials:
From Magnetoelectronics To a Theory of Everything

Nicola Spaldin, UC Santa Barbara

3:00 PM

Poster Session

4:30 PM

Faculty Panel

Top Unanswered Questions in Condensed Matter Physics
Andrea Liu, U Penn
David Pine, NYU
David Schmeltzer, City College
Shivaji Sondhi, Princeton
David Vanderbilt, Rutgers

A panel of faculty from local institutions will compile and discuss a short list of the most pressing, important and relevant questions in the field of condensed matter physics, with help from the audience

5:30 PM

Reception

Speakers

Keynote Speakers

Heinrich Jaeger, PhD

University of Chicago

Nicola Spaldin, PhD

University of California Santa Barbara

Speakers

Cory Dean

Columbia University

Sriram Ganeshan

SUNY Stony Brook

Yuliang Jin

CUNY City College

Douglas H. Kelley

Yale University

Nan Lin

Columbia University

Anil Shrirao

NJ Institute of Technology

Speaker Abstracts

Keynote Presentations

When and How To Walk on Water: A New Perspective on Shear Thickening in Suspensions

Heinrich Jaeger, PhD, University of Chicago

Suspensions of solid particles in simple liquids can exhibit remarkably counter-intuitive behavior. A prototypical example is a mixture of cornstarch in water which appears like a thin liquid when stirred slowly but, when forced more strongly, turns solid-like to the point where it can support a person's weight for a short time, enough to walk across without sinking in. This shear thickening is a form of extreme non-Newtonian response with a viscosity that tends to diverge at a critical shear rate. Traditionally, shear thickening has been interpreted as being driven by hydrodynamic interactions between the particles inside the suspension. This talk will review some recent experimental findings which add up to a new perspective whereby shear thickening can be understood as arising from the interplay between dilation and confinement of the particle arrangement near jamming. This "granular" perspective is independent of any underlying hydrodynamic model and can predict in simple terms the scaling of the stress range over which shear thickening is observable. In particular, it argues that strong shear thickening is a generic property of all suspensions and that it can be recovered even in systems dominated by a large yield stress once this yield stress is reduced sufficiently.

Computational Design of New Multifunctional Materials: From Magnetoelectronics To a Theory of Everything

Nicola Spaldin, PhD, University of California Santa Barbara

Modern computational methods are proving to be invaluable in the first-principles design of new materials with specific targeted functionalities. I will illustrate their utility with two examples from the field of multiferroics: First, the design of new materials for electric-field control of magnetism, and second, testing extensions to the Standard Model by searching for the electric dipole moment of the electron.

Short Talks

Electron transport in graphene on BN

C. R. Dean1,2, A. F. Young 3, P. Kim3, J. Hone2, K. Shepard1
1Department of Electrical Engineering, Columbia University, New York, NY
2Department of Mechanical Engineering, Columbia University, New York, NY
3Department of Physics, Columbia University, New York, New York

Hexagonal BN (h-BN) represents the insulator analogue of graphene, sharing identical crystal structure but with B and N atoms each comprising the two sublattices. Owing to its large bandgap, chemical inertness, hexagonal lattice structure (with only 2% lattice mismatch to graphene), planar (i.e. atomically flat) surface structure and good dielectric properties, single crystal h-BN is an ideal supporting substrate in graphene FET devices. We discuss our investigation of graphene-BN hybrid devices, realized by precision transfer of mechanically exfoliated graphene and single crystal h-BN flakes. We compare device performance of graphene-over-BN with the more conventional graphene-over-SiO2 geometry.  Recent magnetoresistance measurements in ultraclean graphene-on-BN devices are discussed.

Quasiparticle Scattering From Vortices in d-wave Superconductors: Superflow and Berry Phase Contributions

Sriram Ganeshan, SUNY Stony Brook

In the vortex state of a d-wave superconductor, massless Dirac quasiparticles are scattered from magnetic vortices via a combination of two basic mechanisms: effective potential scattering due to the superflow swirling about the vortices and Aharonov-Bohm scattering due to the Berry phase acquired by a quasiparticle upon circling a vortex. In this talk, we present scattering contribution of each of these mechanisms in the absence of the other. First [1], we consider the superflow contribution by calculating the differential cross section for a quasiparticle scattering from the effective non-central potential of a single vortex. Next [2], we consider the Berry phase contribution, which results in branch cuts between neighboring vortices across which the
quasiparticle wave function changes sign. Here, the simplest problem that captures the physics is that of scattering from a single finite branch cut that stretches between two vortices. Elliptical coordinates are natural for this two-center problem and we proceed by separating the massless Dirac equation in elliptical coordinates. Using the method of partial wave analysis, we construct the exact scattering cross section for this case. We summarize the scattering effect of each mechanism, superflow and Berry phase, as a future motivation to study the effect of interference between these two mechanisms in the double vortex setup.
[1] M. Kulkarni, S. Ganeshan, and A. C. Durst, arXiv:1006.2818
[2] S. Ganeshan, M. Kulkarni and A. C. Durst, arXiv:1010.2213

Randomly Packing Spheres

Yuliang Jin, CUNY City College

Randomly packing spheres of equal size into a container consistently results in a static configuration with a density of ~ 64%.  The ubiquity of random close packing (RCP) rather than the optimal crystalline array at 74% begs the question of the physical law behind this empirically deduced state. Indeed, there is no signature of any macroscopic quantity with a discontinuity associated with the observed packing limit. Here we show that RCP can be interpreted as a manifestation of a thermodynamic singularity, which defines it as the ''freezing point'' in a first-order phase transition between ordered and disordered packing phases. Despite the athermal nature of granular matter, we show the thermodynamic character of the transition in that it is accompanied by sharp discontinuities in volume and entropy. This occurs at a critical compactivity, which is the intensive variable that plays the role of temperature in granular matter.  Our results predict the experimental conditions necessary for the formation of a jammed crystal bycalculating an analogue of the ''entropy of fusion''. This approach is useful since it maps out-of-equilibrium
problems in complex systems onto simpler established frameworks in statistical mechanics.

Separating Stretching From Folding in Fluid Mixing

Douglas H. Kelley, Yale University

Efficient large-scale mixing of an impurity in a fluid depends on stretching and folding--together they expand the periphery of material volumes, allowing diffusion to mix at small scales. Yet stretching and folding are difficult to decouple in real flows with complex spatiotempora structure. To separate the two processes, we divide the local fluid deformation into affine and non-affine parts; similar techniques have been used previously to identify shear transformation zones in glassy solids and colloids. We study stretching and folding in a quasi-two-dimensional laboratory flow, measuring its velocity by tracking about 30 000 particles per frame. At short times stretching dominates, but once fluid elements have elongated, folding becomes suddenly stronger and dominates thereafter. The relative strength of the two processes also varies strongly in space. This work is supported by the National Science Foundation.

Dynamical Mean-Field Theory for Quantum Chemistry

Nan Lin, C. A. Marianetti, Andrew J. Millis, and David R. Reichman

The dynamical mean-field concept of approximating an unsolvable many-body problem in terms of the solution of an auxiliary quantum impurity problem, introduced to study bulk materials with a continuous energy spectrum, is here extended to molecules, i.e. finite systems with a discrete energy spectrum. Application to chains and small clusters of hydrogen atoms yields ground state energies which are competitive with leading quantum chemical approaches at intermediate and large interatomic distances, and provides good approximations to the excitation spectrum. The method is a promising approach to the strong correlation problems of quantum chemistry.

Microfluidic Devices Fabricated by Soft-Lithographic Replication of Adhesive Tape for Patterning Biological Cells

Anil Shrirao, Raquel Perez-Castillejos, New Jersey Institute of Technology

We describe a method to fabricate microfluidic devices using only bench-top materials and tools (adhesive tape, scalpel, 65°C oven, glass slides, and PDMS1). We base our developments on soft lithography2, which replicates a master (typically: micropatterned photoresist) in PDMS. But access to photolithography is often limited in non-engineering-focused settings—e.g., medical schools and biology-oriented research centers. Non-photolithographic techniques exist3 and compared to those techniques, ours is the very simplest way to fabricate PDMS devices, as it uses bench-top materials and tools only. First we attach one (or more) tape layer to a glass slide (Fig. 1a) and pattern the tape with a blade following the lines of the design (b,c), removed the extra tape (d), and replicated the master in PDMS (e,f). The tape thickness (~60 µm4) sets the height of the microchannels. Larger heights result from stacking several tape layers. For maximum simplicity, we used a scalpel to pattern the tape with features larger than 0.25 mm—laser cutters or robotic blades could be used for higher precision. We have replicated the same tape master up to 50 times and did not show signs of wearing out.

We used these tape-replicated microfluidic devices to pattern biological cells—in particular, Micro Vascular Endothelial Cells or MVEC. Our results show the viability of the patterned MVE cells for times of culture of up to seven days. After patterning, we released the cells from any spatial constraints and monitored for seven days their migration and proliferation on the surface of the culturing dish.

We believe benchtop fabrication of microdevices will favor the development of microlabs in settings lacking cleanroom facilities, such as biologically-oriented research institutions or teaching-intensive colleges and high schools. Even for those with access to a cleanroom, our method offers rapidity (~1h to fabricate a device), low cost (<$1/device), and safety (no harmful chemicals or UV required).
[1] Information about Dow Corning® brand Silicone Encapsulants, Dow Corning Product Information.
[2] Y. Xia and G. M. Whitesides, Annu. Rev. Sci., 1998, 28: 153-184.
[3] M.S. Thomas, B. Millare, J.M. Clift, D. Bao, C. Hong, and V.I. Vullev. 2010. “Print-and-peel fabrication for microfluidics: what’s in it for biomedical applications?” Ann. Biomed. Eng., 38: 21.
[4] 3M Scotch® Transparent Tape 600; www.3m.com.

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