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Publications

Thermodynamic Signatures of Weyl Fermions in NbP

Cornell Affiliated Author(s)
Author
K. Modic
Tobias Meng
Filip Ronning
Eric Bauer
Philip Moll
B. Ramshaw
Abstract

We present a high magnetic field study of NbP—a member of the monopnictide Weyl semimetal (WSM) family. While the monoarsenides (NbAs and TaAs) have topologically distinct left and right-handed Weyl fermi surfaces, NbP is argued to be “topologically trivial†due to the fact that all pairs of Weyl nodes are encompassed by a single Fermi surface. We use torque magnetometry to measure the magnetic response of NbP up to 60 tesla and uncover a Berry paramagnetic response, characteristic of the topological Weyl nodes, across the entire field range.

Journal
Scientific Reports
Date Published
Funding Source
1752784
715730
Group (Lab)
Brad Ramshaw Group

Transcription factor regulation of RNA polymerase’s torque generation capacity

Cornell Affiliated Author(s)
Author
J. Ma
C. Tan
X. Gao
Fulbright Jr., R.M.
J.W. Roberts
M.D. Wang
Abstract

During transcription, RNA polymerase (RNAP) supercoils DNA as it translocates. The resulting torsional stress in DNA can accumulate and, in the absence of regulatory mechanisms, becomes a barrier to RNAP elongation, causing RNAP stalling, backtracking, and transcriptional arrest. Here we investigate whether and how a transcription factor may regulate both torque-induced Escherichia coli RNAP stalling and the torque generation capacity of RNAP.

Journal
Proceedings of the National Academy of Sciences of the United States of America
Date Published
Research Area
Group (Lab)
Michelle Wang Group

Automated home cage training of mice in a hold-still center-out reach task

Cornell Affiliated Author(s)
Author
T. Bollu
S.C. Whitehead
N. Prasad
J. Walker
N. Shyamkumar
R. Subramaniam
B. Kardon
Itai Cohen
J.H. Goldberg
Abstract

An obstacle to understanding neural mechanisms of movement is the complex, distributed nature of the mammalian motor system. Here we present a novel behavioral paradigm for high-throughput dissection of neural circuits underlying mouse forelimb control. Custom touch-sensing joysticks were used to quantify mouse forelimb trajectories with micron-millisecond spatiotemporal resolution. Joysticks were integrated into computer-controlled, rack-mountable home cages, enabling batches of mice to be trained in parallel.

Journal
Journal of Neurophysiology
Date Published
Funding Source
DP2HD087952
Research Area
Group (Lab)
Itai Cohen Group

Probing many-body interactions in monolayer transition-metal dichalcogenides

Cornell Affiliated Author(s)
Author
D. Van Tuan
B. Scharf
Z. Wang
J. Shan
K.F. Mak
I. Žutić
H. Dery
Abstract

Many-body interactions in monolayer transition-metal dichalcogenides are strongly affected by their unique band structure. We study these interactions by measuring the energy shift of neutral excitons (bound electron-hole pairs) in gated WSe2 and MoSe2. Surprisingly, while the blueshift of the neutral exciton X0 in electron-doped samples can be more than 10 meV, the blueshift in hole-doped samples is nearly absent.

Journal
Physical Review B
Date Published
Funding Source
N000141712793
1410407
1503601
DESC0012635
DESC0013883
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Real-time vibrations of a carbon nanotube

Cornell Affiliated Author(s)
Author
A.W. Barnard
M. Zhang
G.S. Wiederhecker
M. Lipson
P.L. McEuen
Abstract

The field of miniature mechanical oscillators is rapidly evolving, with emerging applications including signal processing, biological detection1 and fundamental tests of quantum mechanics2. As the dimensions of a mechanical oscillator shrink to the molecular scale, such as in a carbon nanotube resonator3–7, their vibrations become increasingly coupled and strongly interacting8,9 until even weak thermal fluctuations could make the oscillator nonlinear10–13.

Journal
Nature
Date Published
Funding Source
DGE-0654193
ECCS-1542081
DMR-1719875
0928552
2012/17765-7
Group (Lab)
Paul McEuen Group

Thickness dependence of superconductivity in ultrathin NbS2

Cornell Affiliated Author(s)
Author
R. Yan
G. Khalsa
B.T. Schaefer
A. Jarjour
S. Rouvimov
K.C. Nowack
H.G. Xing
D. Jena
Abstract

We report a systematic study of thickness-dependent superconductivity and carrier transport properties in exfoliated layered 2H-NbS2. Hall-effect measurements reveal 2H-NbS2 is a p-type metal with hole mobility of 1-3 cm2 V-1s-1. The superconducting transition temperature is found to decrease with thickness. However, we find that superconductivity is suppressed due to disorder resulting from the incorporation of atmospheric oxygen.

Journal
Applied Physics Express
Date Published
Funding Source
DMR-1719875
1433490
1542081
Group (Lab)
Katja Nowack Group

Chlorine evolution reaction electrocatalysis on RuO2(110) and IrO2(110) grown using molecular-beam epitaxy

Cornell Affiliated Author(s)
Author
D.-Y. Kuo
H. Paik
J.N. Nelson
K.M. Shen
D.G. Schlom
J. Suntivich
Abstract

We report the electrocatalysis of the chlorine evolution reaction (CER) on well-defined RuO2(110) and IrO2(110) surfaces. RuO2 and IrO2 are known for their capabilities to catalyze the CER. Until now, the CER measurements have only been reported on well-defined RuO2 surfaces and only at high Cl- concentrations. We present the CER measurement and the role of Cl- at lower concentration on single-orientation RuO2(110) and IrO2(110) films. We find that RuO2(110) is two orders of magnitude more active than IrO2(110).

Journal
Journal of Chemical Physics
Date Published
Funding Source
DMR-1719875
ECCS1542081
Group (Lab)
Kyle Shen Group

Kirigami Mechanics as Stress Relief by Elastic Charges

Cornell Affiliated Author(s)
Author
M. Moshe
E. Esposito
S. Shankar
B. Bircan
Itai Cohen
D.R. Nelson
M.J. Bowick
Abstract

We develop a geometric approach to understand the mechanics of perforated thin elastic sheets, using the method of strain-dependent image elastic charges. This technique recognizes the buckling response of a hole under an external load as a geometrically tuned mechanism of stress relief. We use a diagonally pulled square paper frame as a model system to quantitatively test and validate our approach. Specifically, we compare nonlinear force-extension curves and global displacement fields in theory and experiment.

Journal
Physical Review Letters
Date Published
Funding Source
PHY-1125915
DMREF-1435999
PHY-1748958
1125915
1420570
1435794
1435829
1435999
Group (Lab)
Itai Cohen Group

Nonlinear mechanics of thin frames

Cornell Affiliated Author(s)
Author
M. Moshe
E. Esposito
S. Shankar
B. Bircan
Itai Cohen
D.R. Nelson
M.J. Bowick
Abstract

The dramatic effect kirigami, such as hole cutting, has on the elastic properties of thin sheets invites a study of the mechanics of thin elastic frames under an external load. Such frames can be thought of as modular elements needed to build any kirigami pattern. Here we develop the technique of elastic charges to address a variety of elastic problems involving thin sheets with perforations, focusing on frames with sharp corners. We find that holes generate elastic defects (partial disclinations), which act as sources of geometric incompatibility.

Journal
Physical Review E
Date Published
Funding Source
DMR-1435829
DMREF-1435794
DMREF-1435999
PHY-1748958
1125915
1420570
1435794
1435999
DMR-1420570
Group (Lab)
Itai Cohen Group