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Publications

Current-Induced Torques with Dresselhaus Symmetry Due to Resistance Anisotropy in 2D Materials

Cornell Affiliated Author(s)
Author
Gregory Stiehl
David MacNeill
Nikhil Sivadas
Ismail Baggari
Marcos Guimarães
Neal Reynolds
Lena Kourkoutis
Craig Fennie
Robert Buhrman
Daniel Ralph
Abstract

We report measurements of current-induced torques in heterostructures of Permalloy (Py) with TaTe2, a transition-metal dichalcogenide (TMD) material possessing low crystal symmetry, and observe a torque component with Dresselhaus symmetry. We suggest that the dominant mechanism for this Dresselhaus component is not a spin-orbit torque but rather the Oersted field arising from a component of current that flows perpendicular to the applied voltage due to resistance anisotropy within the TaTe2.

Journal
American Chemical Society (ACS)
Date Published
Funding Source
Rubicon 680-50-1311
DE-SC0017671
1429155
1542081
1708499
1719875
DMR-1539918
DMR-1708499
DMR-1719875
ECCS-1542081
NSF-MRI-1429155
680-50-1311

The electronic complexity of the ground-state of the FeMo cofactor of nitrogenase as relevant to quantum simulations

Cornell Affiliated Author(s)
Author
Zhendong Li
Junhao Li
Nikesh Dattani
C. Umrigar
Garnet Chan
Abstract

We report that a recent active space model of the nitrogenase FeMo cofactor, proposed in the context of simulations on quantum computers, is not representative of the electronic structure of the FeMo cofactor ground-state. A more representative model does not affect much certain resource estimates for a quantum computer such as the cost of a Trotter step, while strongly affecting others such as the cost of adiabatic state preparation.

Journal
Journal of Chemical Physics
Date Published
Funding Source
1665333
ACI-1445606
Group (Lab)
Cyrus Umrigar Group

A wave of WNT signaling balanced by secreted inhibitors controls primitive streak formation in micropattern colonies of human embryonic stem cells

Cornell Affiliated Author(s)
Author
I. Martyn
A.H. Brivanlou
E.D. Siggia
Abstract

Long-range signaling by morphogens and their inhibitors define embryonic patterning yet quantitative data and models are rare, especially in humans. Here, we use a human embryonic stem cell micropattern system to model formation of the primitive streak (PS) by WNT. In the pluripotent state, E-cadherin (E-CAD) transduces boundary forces to focus WNT signaling to the colony border. Following application of WNT ligand, E-CAD mediates a front or wave of epithelial-to-mesenchymal (EMT) conversion analogous to PS extension in an embryo.

Journal
Development (Cambridge)
Date Published
Funding Source
PHY 1502151
R01 HD080699
R01GM101653
Research Area

Intermittent plasticity in individual grains: A study using high energy x-ray diffraction

Cornell Affiliated Author(s)
Author
K. Chatterjee
A.J. Beaudoin
D.C. Pagan
P.A. Shade
H.T. Philipp
M.W. Tate
Sol Gruner
P. Kenesei
J.-S. Park
Abstract

Long-standing evidence suggests that plasticity in metals may proceed in an intermittent fashion. While the documentation of intermittency in plastically deforming materials has been achieved in several experimental settings, efforts to draw connections from dislocation motion and structure development to stress relaxation have been limited, especially in the bulk of deforming polycrystals.

Journal
Structural Dynamics
Date Published
Funding Source
DE-SC0017631
1332208
Group (Lab)
Sol M. Gruner Group

Mapping cell migrations and fates in a gastruloid model to the human primitive streak

Cornell Affiliated Author(s)
Author
I. Martyn
E.D. Siggia
A.H. Brivanlou
Abstract

Although fate maps of early embryos exist for nearly all model organisms, a fate map of the gastrulating human embryo remains elusive. Here, we use human gastruloids to piece together a rudimentary fate map for the human primitive streak (PS). This is possible because differing levels of BMP, WNT and NODAL lead to self-organization of gastruloids into homogenous subpopulations of endoderm and mesoderm, and comparative analysis of these gastruloids, together with the fate map of the mouse embryo, allows the organization of these subpopulations along an anterior-posterior axis.

Journal
Development (Cambridge)
Date Published
Funding Source
R01 GM101653
R01HD080699
Research Area

Monotone learning with rectified wire networks

Cornell Affiliated Author(s)
Author
V. Elser
D. Schmidt
J. Yedidia
Abstract

We introduce a new neural network model, together with a tractable and monotone online learning algorithm. Our model describes feed-forward networks for classification, with one output node for each class. The only nonlinear operation is rectification using a ReLU function with a bias. However, there is a rectifier on every edge rather than at the nodes of the network. There are also weights, but these are positive, static, and associated with the nodes. Our rectified wire networks are able to represent arbitrary Boolean functions.

Journal
Journal of Machine Learning Research
Date Published
Group (Lab)
Veit Elser Group

Tools for change: Measuring student conceptual understanding across undergraduate biology programs using bio-maps assessments

Cornell Affiliated Author(s)
Author
M.K. Smith
S.E. Brownell
A.J. Crowe
N.G. Holmes
J.K. Knight
K. Semsar
M.M. Summers
C. Walsh
C.D. Wright
B.A. Couch
Abstract

Assessing learning across a biology major can help departments monitor achievement of broader program-level goals and identify opportunities for curricular improvement. However, biology departments have lacked suitable tools to measure learning at the program scale. To address this need, we developed four freely available assessments called Biology-Measuring Achievement and Progression in Science or Bio-MAPS for general biology, molecular biology, ecology/evolution, and physiology programs.

Journal
Journal of Microbiology and Biology Education
Date Published
Funding Source
DUE-1322364
DUE-1322556
DUE-1323010
1322364

Vector-resolved magnetooptic kerr effect measurements of spin-orbit torque

Cornell Affiliated Author(s)
Author
Halise Celik
H. Kannan
T. Wang
A.R. Mellnik
X. Fan
X. Zhou
R. Barri
D.C. Ralph
M.F. Doty
V.O. Lorenz
J.Q. Xiao
Abstract

We demonstrate simultaneous detection of current-driven dampinglike and fieldlike spin-orbit torques in heavy metal/ferromagnetic metal bilayers by measuring all three magnetization components mx,my, and mz using a vector-resolved magnetooptic Kerr effect (MOKE) technique based on quadrant detection. We investigate the magnitude and direction of spin-orbit torques in a series of platinum/permalloy samples, finding good agreement with results obtained via polar and quadratic MOKE measurements without quadrant detection. © 1965-2012 IEEE.

Journal
IEEE Transactions on Magnetics
Date Published
Funding Source
1624976
DMR-1624976
DE-SC0016380

Visualizing electronic quantum matter

Cornell Affiliated Author(s)
Author
K. Fujita
M.H. Hamidian
P.O. Sprau
S.D. Edkins
J.C.S. Davis
Abstract

Modern quantum materials support a wide variety of exotic and unanticipated states of quantum matter and differ radically in phenomenology from conventional systems such as metals, semiconductors, band insulators, and ferromagnets. For example, quantum materials exhibit states such as electron liquid crystals, fluids of fractionalized quantum particles, quantum-entangled spin liquids, and topologically protected composite quantum particles.

Journal
Springer Handbooks
Date Published
Group (Lab)
J.C. Seamus Davis Group

High-Performance Image-Based Measurements of Biological Forces and Interactions in a Dual Optical Trap

Cornell Affiliated Author(s)
Author
J.L. Killian
J.T. Inman
M.D. Wang
Abstract

Optical traps enable the nanoscale manipulation of individual biomolecules while measuring molecular forces and lengths. This ability relies on the sensitive detection of optically trapped particles, typically accomplished using laser-based interferometric methods. Recently, image-based particle tracking techniques have garnered increased interest as a potential alternative to laser-based detection; however, successful integration of image-based methods into optical trapping instruments for biophysical applications and force measurements has remained elusive.

Journal
ACS Nano
Date Published
Research Area
Group (Lab)
Michelle Wang Group