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Publications

Monolithic gyroidal mesoporous mixed titanium-niobium nitrides

Cornell Affiliated Author(s)
Author
S.W. Robbins
H. Sai
F.J. DiSalvo
Sol Gruner
U. Wiesner
Abstract

Mesoporous transition metal nitrides are interesting materials for energy conversion and storage applications due to their conductivity and durability. We present ordered mixed titanium-niobium (8:2, 1:1) nitrides with gyroidal network structures synthesized from triblock terpolymer structure-directed mixed oxides. The materials retain both macroscopic integrity and mesoscale ordering despite heat treatment up to 600 °C, without a rigid carbon framework as a support. Furthermore, the gyroidal lattice parameters were varied by changing polymer molar mass.

Journal
ACS Nano
Date Published
Research Area
Group (Lab)
Sol M. Gruner Group

Possible topological superconducting phases of MoS2

Cornell Affiliated Author(s)
Author
N.F.Q. Yuan
K.F. Mak
K.T. Law
Abstract

Molybdenum disulphide (MoS2) has attracted much interest in recent years due to its potential applications in a new generation of electronic devices. Recently, it was shown that thin films of MoS2 can become superconducting with a highest Tc of 10 K when the material is heavily gated to the conducting regime. In this work, using the group theoretical approach, we determine the possible pairing symmetries of heavily gated MoS2.

Journal
Physical Review Letters
Date Published
Group (Lab)
Kin Fai Mak Group

Correlated vs. conventional insulating behavior in the Jeff= 12 vs. 32 bands in the layered iridate Ba2 IrO4

Cornell Affiliated Author(s)
Author
M. Uchida
Y.F. Nie
P.D.C. King
C.H. Kim
C.J. Fennie
D.G. Schlom
K.M. Shen
Abstract

We employ molecular beam epitaxy to stabilize Ba2IrO4 thin films and utilize in situ angle-resolved photoemission spectroscopy to investigate the evolution of its electronic structure through the Néel temperature TN. Our measurements indicate that dispersions of the relativistic Jeff=1/2 and 3/2 bands exhibit an unusual dichotomy in their behavior through the Néel transition.

Journal
Physical Review B - Condensed Matter and Materials Physics
Date Published
Funding Source
FA9550-11-1-0033
FA9550-12-1-0035
DMR-1120296
1120296
Group (Lab)
Kyle Shen Group

Direct evidence for a magnetic f-electron-mediated pairing mechanism of heavy-fermion superconductivity in CeCoIn5

Cornell Affiliated Author(s)
Author
J.S. Van Dyke
F. Massee
M.P. Allan
J.C.S. Davis
C. Petrovic
D.K. Morr
Abstract

To identify the microscopic mechanism of heavy-fermion Cooper pairing is an unresolved challenge in quantum matter studies; it may also relate closely to finding the pairing mechanism of hightemperature superconductivity. Magnetically mediated Cooper pairing has long been the conjectured basis of heavy-fermion superconductivity but no direct verification of this hypothesis was achievable.

Journal
Proceedings of the National Academy of Sciences of the United States of America
Date Published
Group (Lab)
J.C. Seamus Davis Group

Single layer graphene as an electrochemical platform

Cornell Affiliated Author(s)
Author
Nicole Ritzert
Wan Li
Cen Tan
Gabriel Rodríguez-Calero
Joaquín Rodríguez-López
Kenneth Hernández-Burgos
Sean Conte
Joshua Parks
Daniel Ralph
Héctor Abruña
Abstract

Over the past decade, there has been a great deal of interest in graphene with regards to its electrochemical behavior. Previous studies have focused on understanding fundamental processes such as charge transfer and molecular transport at the graphene-electrolyte interface as well as on applications of graphene in electronic, optical, and mechanical systems. We present illustrative examples of large area, single layer graphene platforms for applications such as optical and sensing devices as well as microfluidic systems.

Journal
Royal Society of Chemistry (RSC)
Date Published

Using origami design principles to fold reprogrammable mechanical metamaterials

Cornell Affiliated Author(s)
Author
J.L. Silverberg
A.A. Evans
L. McLeod
R.C. Hayward
T. Hull
C.D. Santangelo
Itai Cohen
Abstract

Although broadly admired for its aesthetic qualities, the art of origami is now being recognized also as a framework for mechanical metamaterial design.Working with the Miura-ori tessellation, we find that each unit cell of this crease pattern is mechanically bistable, and by switching between states, the compressive modulus of the overall structure can be rationally and reversibly tuned. By virtue of their interactions, these mechanically stable lattice defects also lead to emergent crystallographic structures such as vacancies, dislocations, and grain boundaries.

Journal
Science
Date Published
Funding Source
1240441
Group (Lab)
Itai Cohen Group

Heating from continuous number density measurements in optical lattices

Cornell Affiliated Author(s)
Author
Y. Yanay
E.J. Mueller
Abstract

We explore the effects of continuous number density measurement on atoms in an optical lattice. By integrating a master equation for quantum observables, we calculate how single-particle correlations decay. We consider weakly and strongly interacting bosons and noninteracting fermions. Even in the Mott regime, such measurements destroy correlations and increase the average energy, as long as some hopping is allowed. We explore the role of spatial resolution and find that the heating rate is proportional to the amount of information gained from such measurements.

Journal
Physical Review A - Atomic, Molecular, and Optical Physics
Date Published
Funding Source
63834-PH-MUR

Predicting fruit fly's sensing rate with insect flight simulations

Cornell Affiliated Author(s)
Author
S. Chang
Z.J. Wang
Abstract

Without sensory feedback, flies cannot fly. Exactly how various feedback controls work in insects is a complex puzzle to solve. What do insects measure to st abilize their flight? How often and how fast must insects adjust their wings to remain stable? To gain insights into algorithms used by insects to control their dynamic instability, we develop a simulation tool to study free flight. To stabilize flight, we construct a control algorithm that modulates wing motion based on discrete measurements of the body-pitch orientation.

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

Atomically precise interfaces from non-stoichiometric deposition

Cornell Affiliated Author(s)
Author
Y.F. Nie
Y. Zhu
C.-H. Lee
L.F. Kourkoutis
J.A. Mundy
J. Junquera
P. Ghosez
D.J. Baek
S. Sung
X.X. Xi
K.M. Shen
D.A. Muller
D.G. Schlom
Abstract

Complex oxide heterostructures display some of the most chemically abrupt, atomically precise interfaces, which is advantageous when constructing new interface phases with emergent properties by juxtaposing incompatible ground states. One might assume that atomically precise interfaces result from stoichiometric growth. Here we show that the most precise control is, however, obtained by using deliberate and specific non-stoichiometric growth conditions.

Journal
Nature Communications
Date Published
Funding Source
DMR-1120296
ECCS-0335765
IMR-0417392
W911NF-09-1-0415
W911NF-12-1-0437
FIS2012-37549-C05-04
Group (Lab)
Kyle Shen Group

A method to recapitulate early embryonic spatial patterning in human embryonic stem cells

Cornell Affiliated Author(s)
Author
A. Warmflash
B. Sorre
F. Etoc
E.D. Siggia
A.H. Brivanlou
Abstract

Embryos allocate cells to the three germ layers in a spatially ordered sequence. human embryonic stem cells (hescs) can generate the three germ layers in culture; however, differentiation is typically heterogeneous and spatially disordered. We show that geometric confnement is suffcient to trigger self-organized patterning in hescs. in response to BmP4, colonies reproducibly differentiated to an outer trophectoderm-like ring, an inner ectodermal circle and a ring of mesendoderm expressing primitive-streak markers in between.

Journal
Nature Methods
Date Published
Funding Source
R01GM101653
R01HD032105
PHY-0954398
Research Area