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Publications

Superheating field of superconductors within Ginzburg-Landau theory

Cornell Affiliated Author(s)
Author
M.K. Transtrum
G. Catelani
J.P. Sethna
Abstract

We study the superheating field of a bulk superconductor within Ginzburg-Landau theory, which is valid near the critical temperature. We calculate, as functions of the Ginzburg-Landau parameter κ, the superheating field Hsh and the critical momentum kc characterizing the wavelength of the instability of the Meissner state to flux penetration. By mapping the two-dimensional linear stability theory into a one-dimensional eigenfunction problem for an ordinary differential equation, we solve the problem numerically.

Journal
Physical Review B - Condensed Matter and Materials Physics
Date Published
Funding Source
1005479
0705167
Group (Lab)
James Sethna Group

Geometry of nonlinear least squares with applications to sloppy models and optimization

Cornell Affiliated Author(s)
Author
M.K. Transtrum
B.B. Machta
J.P. Sethna
Abstract

Parameter estimation by nonlinear least-squares minimization is a common problem that has an elegant geometric interpretation: the possible parameter values of a model induce a manifold within the space of data predictions. The minimization problem is then to find the point on the manifold closest to the experimental data. We show that the model manifolds of a large class of models, known as sloppy models, have many universal features; they are characterized by a geometric series of widths, extrinsic curvatures, and parameter-effect curvatures, which we describe as a hyper-ribbon.

Journal
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics
Date Published
Funding Source
0705167
Group (Lab)
James Sethna Group

Angle dependence of quantum oscillations in YBa 2 Cu 3 O 6.59 shows free-spin behaviour of quasiparticles

Cornell Affiliated Author(s)
Author
B.J. Ramshaw
B. Vignolle
J. Day
R. Liang
W.N. Hardy
C. Proust
D.A. Bonn
Abstract

Measurements of quantum oscillations in the cuprate superconductors afford an opportunity to assess the extent to which their electronic properties yield to a description rooted in Fermi-liquid theory. However, such an analysis is hampered by the small number of oscillatory periods observed in the accessible magnetic field range. Here we employ a genetic algorithm to globally model the field, angular and temperature dependence of the quantum oscillations observed in the resistivity of YBa 2 Cu 3 O 6.59 .

Journal
Nature Physics
Date Published
Group (Lab)
Brad Ramshaw Group

Scatterometry measurement for gate ADI and AEI critical dimension of 28-nm metal gate technology

Cornell Affiliated Author(s)
Author
Y.-H. Huang
H. Chen
K. Shen
H.H. Chen
C.C. Yu
J.H. Liao
X. Zhang
R. Teo
Z.-Q. Xu
S. Yoo
C.-H. Lin
C.-Y. Cheng
J. Lin
Abstract

This paper discusses the scatterometry-based metrology measurement of 28nm high k metal gate after-develop inspection (ADI) and after-etch inspection (AEI) layer structures. For these structures, the critical measurement parameters include side wall angle (SWA) and critical dimension (CD). For production process control of these structures, a metrology tool must utilize a non-destructive measurement technique, and have high sensitivity, precision and throughput.

Conference Name
Conference
Date Published
Group (Lab)
Kyle Shen Group

Small-angle solution scattering using the mixed-mode pixel array detector

Cornell Affiliated Author(s)
Author
L.J. Koerner
R.E. Gillilan
K.S. Green
S. Wang
Sol Gruner
Abstract

Solution small-angle X-ray scattering (SAXS) measurements were obtained using a 128 X 128 pixel X-ray mixed-mode pixel array detector (MMPAD) with an 860 μs readout time. The MMPAD offers advantages for SAXS experiments: a pixel full-well of >2 × 107 10 keV X-rays, a maximum flux rate of 108 X-rays pixel-1 s-1, and a sub-pixel point-spread function. Data from the MMPAD were quantitatively compared with data from a charge-coupled device (CCD) fiber-optically coupled to a phosphor screen.

Journal
Journal of Synchrotron Radiation
Date Published
Group (Lab)
Sol M. Gruner Group

X-ray analog pixel array detector for single synchrotron bunch time-resolved imaging

Cornell Affiliated Author(s)
Author
L.J. Koerner
Sol Gruner
Abstract

Dynamic X-ray studies can reach temporal resolutions limited by only the X-ray pulse duration if the detector is fast enough to segregate synchrotron pulses. An analog integrating pixel array detector with in-pixel storage and temporal resolution of around 150 ns, sufficient to isolate pulses, is presented. Analog integration minimizes count-rate limitations and in-pixel storage captures successive pulses. Fundamental tests of noise and linearity as well as high-speed laser measurements are shown.

Journal
Journal of Synchrotron Radiation
Date Published
Group (Lab)
Sol M. Gruner Group

Quantum Monte Carlo with Jastrow-valence-bond wave functions

Cornell Affiliated Author(s)
Author
Benoît Braïda
Julien Toulouse
Michel Caffarel
C. Umrigar
Abstract

We consider the use in quantum Monte Carlo calculations of two types of valence bond wave functions based on strictly localized active orbitals, namely valence bond self-consistent-field and breathing-orbital valence bond wave functions. Complemented by a Jastrow factor, these Jastrow-valence-bond wave functions are tested by computing the equilibrium well depths of the four diatomic molecules C2, N2, O2, and F 2 in both variational Monte Carlo and diffusion Monte Carlo.

Journal
Journal of Chemical Physics
Date Published
Group (Lab)
Cyrus Umrigar Group

Basis set construction for molecular electronic structure theory: Natural orbital and Gauss-Slater basis for smooth pseudopotentials

Cornell Affiliated Author(s)
Author
F.R. Petruzielo
J. Toulouse
C.J. Umrigar
Abstract

A simple yet general method for constructing basis sets for molecular electronic structure calculations is presented. These basis sets consist of atomic natural orbitals from a multiconfigurational self-consistent field calculation supplemented with primitive functions, chosen such that the asymptotics are appropriate for the potential of the system. Primitives are optimized for the homonuclear diatomic molecule to produce a balanced basis set. Two general features that facilitate this basis construction are demonstrated.

Journal
Journal of Chemical Physics
Date Published
Funding Source
CHE-1004603
DMR-0908653
0908653
1004603
Group (Lab)
Cyrus Umrigar Group

Lifshitz critical point in the cuprate superconductor YBa 2Cu3Oy from high-field Hall effect measurements

Cornell Affiliated Author(s)
Author
David LeBoeuf
Nicolas Doiron-Leyraud
B. Vignolle
Mike Sutherland
B. Ramshaw
J. Levallois
R. Daou
Francis Laliberté
Olivier Cyr-Choinière
Johan Chang
Y. Jo
L. Balicas
Ruixing Liang
D. Bonn
W. Hardy
Cyril Proust
Louis Taillefer
Abstract

The Hall coefficient RH of the cuprate superconductor YBa 2Cu3Oy was measured in magnetic fields up to 60 T for a hole concentration p from 0.078 to 0.152 in the underdoped regime. In fields large enough to suppress superconductivity, RH(T) is seen to go from positive at high temperature to negative at low temperature, for p0.08. This change of sign is attributed to the emergence of an electron pocket in the Fermi surface at low temperature. At p<0.08, the normal-state R H(T) remains positive at all temperatures, increasing monotonically as T→0.

Journal
Physical Review B - Condensed Matter and Materials Physics
Date Published
Group (Lab)
Brad Ramshaw Group

Mass coupling and Q -1 of impurity-limited normal 3He in a torsion pendulum

Cornell Affiliated Author(s)
Author
R.G. Bennett
N. Zhelev
A.D. Fefferman
K.Y. Fang
J. Pollanen
P. Sharma
W.P. Halperin
J.M. Parpia
Abstract

We present results of the Q -1 and period shift, ΔP, for 3He confined in a 98% nominal open aerogel on a torsion pendulum. The aerogel is compressed uniaxially by 10% along a direction aligned to the torsion pendulum axis and was grown within a 400 μm tall pancake (after compression) similar to an Andronikashvili geometry. The result is a high Q pendulum able to resolve Q -1 and mass coupling of the impurity-limited 3He over the whole temperature range.

Journal
Journal of Low Temperature Physics
Date Published
Funding Source
DMR-0703656
DMR-0806629
0703656
0806629
Group (Lab)
Jeevak Parpia Group