3,828 research outputs found
The fate of quasiparticles in the superconducting state
Quasiparticle properties in the superconducting state are masked by the
superfluid and are not directly accessible to infrared spectroscopy. We show
how one can use a Kramers--Kronig transformation to separate the quasiparticle
from superfluid response and extract intrinsic quasiparticle properties in the
superconducting state. We also address the issue of a narrow quasiparticle peak
observed in microwave measurements, and demonstrate how it can be combined with
infrared measurements to obtain unified picture of electrodynamic properties of
cuprate superconductors
ScGAN: A Generative Adversarial Network to Predict Hypothetical Superconductors
Despite having been discovered more than three decades ago, High Temperature
Superconductors (HTSs) lack both an explanation for their mechanisms and a
systematic way to search for them. To aid this search, this project proposes
ScGAN, a Generative Adversarial Network (GAN) to efficiently predict new
superconductors. ScGAN was trained on compounds in OQMD and then transfer
learned onto the SuperCon database or a subset of it. Once trained, the GAN was
used to predict superconducting candidates, and approximately 70\% of them were
determined to be superconducting by a classification model--a 23-fold increase
in discovery rate compared to manual search methods. Furthermore, more than
99\% of predictions were novel materials, demonstrating that ScGAN was able to
potentially predict completely new superconductors, including several promising
HTS candidates. This project presents a novel, efficient way to search for new
superconductors, which may be used in technological applications or provide
insight into the unsolved problem of high temperature superconductivity
An Infrared study of the Josephson vortex state in high-Tc cuprates
We report the results of the c-axis infrared spectroscopy of La_{2-x} Sr_x
CuO_4 in high magnetic field oriented parallel to the CuO_2 planes. A
significant suppression of the superfluid density with magnetic field rho_s(H)
is observed for both underdoped (x=0.125) and overdoped (x=0.17) samples. We
show that the existing theoretical models of the Josephson vortex state fail to
consistently describe the observed effects and discuss possible reasons for the
discrepancies
Heavy fermion fluid in high magnetic fields: an infrared study of CeRuSb
We report a comprehensive infrared magneto-spectroscopy study of
CeRuSb compound revealing quasiparticles with heavy effective mass
m, with a detailed analysis of optical constants in fields up to 17 T. We
find that the applied magnetic field strongly affects the low energy
excitations in the system. In particular, the magnitude of m 70
m (m is the quasiparticle band mass) at 10 K is suppressed by as much
as 25 % at 17 T. This effect is in quantitative agreement with the mean-field
solution of the periodic Anderson model augmented with a Zeeman term
Electronic Structure and Charge Dynamics of Huesler Alloy Fe2TiSn Probed by Infrared and Optical Spectroscopy
We report on the electrodynamics of a Heusler alloy Fe2TiSn probed over four
decades in energy: from the far infrared to the ultraviolet. Our results do not
support the suggestion of Kondo-lattice behavior inferred from specific heat
measurements. Instead, we find a conventional Drude-like response of free
carriers, with two additional absorption bands centered at around 0.1 and 0.87
eV. The latter feature can be interpreted as excitations across a pseudogap, in
accord with band structure calculations.Comment: 3 pages, 4 figure
Signatures of electron-boson coupling in half-metallic ferromagnet MnGe: study of electron self-energy obtained from infrared spectroscopy
We report results of our infrared and optical spectroscopy study of a
half-metallic ferromagnet MnGe. This compound is currently being
investigated as a potential injector of spin polarized currents into germanium.
Infrared measurements have been performed over a broad frequency (50 - 50000
cm) and temperature (10 - 300 K) range. From the complex optical
conductivity we extract the electron self-energy
. The calculation of is based on novel
numerical algorithms for solution of systems of non-linear equations. The
obtained self-energy provides a new insight into electron correlations in
MnGe. In particular, it reveals that charge carriers may be coupled to
bosonic modes, possibly of magnetic origin
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