142 research outputs found
Unconventional Charge Ordering in Na0.70CoO2 below 300 K
We present the results of measurements of the dc-magnetic susceptibility
chi(T) and the 23Na-NMR response of Na_{0.70}CoO_{2} at temperatures between 50
and 340 K. The chi(T) data suggest that for T > 75 K, the Co ions adopt an
effective configuration of Co^{3.4+}. The 23Na-NMR response reveals pronounced
anomalies near 250 and 295 K, but no evidence for magnetic phase transitions is
found in chi(T). Our data suggest the onset of a dramatic change in the Co
3d-electron spin dynamics at 295 K. This process is completed at 230 K. Our
results maybe interpreted as evidence for either a tendency to electron
localization or an unconventional charge-density wave phenomenon within the
cobalt oxide layer, CoO_2, 3d electron system near room temperature.Comment: 4 pages, 4 figures, re-submitted to Physical Review Letters. The
manuscript has been revised following the recommendations of the referees.
The discussion section contains substantial change
Single-particle nonlocality and entanglement with the vacuum
We propose a single-particle experiment that is equivalent to the
conventional two-particle experiment used to demonstrate a violation of Bell's
inequalities. Hence, we argue that quantum mechanical nonlocality can be
demonstrated by single-particle states. The validity of such a claim has been
discussed in the literature, but without reaching a clear consensus. We show
that the disagreement can be traced to what part of the total state of the
experiment one assigns to the (macroscopic) measurement apparatus. However,
with a conventional and legitimate interpretation of the measurement process
one is led to the conclusion that even a single particle can show nonlocal
properties.Comment: 6 pages, 5 figure
Magnetic field-dependent interplay between incoherent and Fermi liquid transport mechanisms in low-dimensional tau phase organic conductors
We present an electrical transport study of the 2-dimensional (2D) organic
conductor tau-(P-(S,S)-DMEDT-TTF)_2(AuBr)_2(AuBr_2)_y (y = 0.75) at low
temperatures and high magnetic fields. The inter-plane resistivity rho_zz
increases with decreasing temperature, with the exception of a slight anomaly
at 12 K. Under a magnetic field B, both rho_zz and the in-plane resistivity
plane rho_xx show a pronounced negative and hysteretic magnetoresistance with
Shubnikov de Haas (SdH)oscillations being observed in some (high
quality)samples above 15 T. Contrary to the predicted single, star-shaped,
closed orbit Fermi surface from band structure calculations (with an expected
approximate area of 12.5% of A_FBZ), two fundamental frequencies F_l and F_h
are detected in the SdH signal. These orbits correspond to 2.4% and 6.8% of the
area of the first Brillouin zone(A_FBZ), with effective masses F_l = 4.0 +/-
0.5 and F_h = 7.3 +/- 0.1. The angular dependence, in tilted magnetic fields of
F_l and F_h, reveals the 2D character of the FS and Angular dependent
magnetoresistance (AMRO) further suggests a FS which is strictly 2-D where the
inter-plane hopping t_c is virtually absent or incoherent. The Hall constant
R_xy is field independent, and the Hall mobility increases by a factor of 3
under moderate magnetic fields. Our observations suggest a unique physical
situation where a stable 2D Fermi liquid state in the molecular layers are
incoherently coupled along the least conducting direction. The magnetic field
not only reduces the inelastic scattering between the 2D metallic layers, but
it also reveals the incoherent nature of interplane transport in the AMRO
spectrum. The apparent ferromagnetism of the hysteretic magnetoresistance
remains an unsolved problem.Comment: 33 pages, 11 figure
Electronic correlation in the infrared optical properties of the quasi two dimensional -type BEDT-TTF dimer system
The polarized optical reflectance spectra of the quasi two dimensional
organic correlated electron system -(BEDT-TTF)Cu[N(CN)],
Br and Cl are measured in the infrared region. The former shows the
superconductivity at 11.6 K and the latter does the
antiferromagnetic insulator transition at 28 K. Both the
specific molecular vibration mode of the BEDT-TTF molecule and
the optical conductivity hump in the mid-infrared region change correlatively
at 38 K of -(BEDT-TTF)Cu[N(CN)]Br, although
no indication of but the insulating behaviour below 50-60 K are found in -(BEDT-TTF)Cu[N(CN)]Cl. The
results suggest that the electron-molecular vibration coupling on the
mode becomes weak due to the enhancement of the itinerant
nature of the carriers on the dimer of the BEDT-TTF molecules below ,
while it does strong below because of the localized carriers on
the dimer. These changes are in agreement with the reduction and the
enhancement of the mid-infrared conductivity hump below and , respectively, which originates from the transitions between the upper
and lower Mott-Hubbard bands. The present observations demonstrate that two
different metallic states of -(BEDT-TTF)Cu[N(CN)]Br are
regarded as {\it a correlated good metal} below including the
superconducting state and {\it a half filling bad metal} above . In
contrast the insulating state of -(BEDT-TTF)Cu[N(CN)]Cl
below is the Mott insulator.Comment: 8 pages, 7 figure
Zero-bias conductance peak splitting due to multiband effect in tunneling spectroscopy
We study how the multiplicity of the Fermi surface affects the zero-bias peak
in conductance spectra of tunneling spectroscopy. As case studies, we consider
models for organic superconductors -(BEDT-TTF)Cu(NCS) and
(TMTSF)ClO. We find that multiplicity of the Fermi surfaces can lead to
a splitting of the zero-bias conductance peak (ZBCP). We propose that the
presence/absence of the ZBCP splitting is used as a probe to distinguish the
pairing symmetry in -(BEDT-TTF)Cu(NCS).Comment: 7 pages, 7 figure
Event reconstruction for KM3NeT/ORCA using convolutional neural networks
The authors acknowledge the financial support of the funding agencies: Agence Nationale de la Recherche (contract ANR-15-CE31-0020), Centre National de la Recherche Scientifique (CNRS), Commission Europeenne (FEDER fund and Marie Curie Program), Institut Universitaire de France (IUF), LabEx UnivEarthS (ANR-10-LABX-0023 and ANR-18-IDEX-0001), Paris Ile-de-France Region, France; Shota Rustaveli National Science Foundation of Georgia (SRNSFG, FR-18-1268), Georgia; Deutsche Forschungsgemeinschaft (DFG), Germany; The General Secretariat of Research and Technology (GSRT), Greece; Istituto Nazionale di Fisica Nucleare (INFN), Ministero dell'Universita e della Ricerca (MUR), PRIN 2017 program (Grant NAT-NET 2017W4HA7S) Italy; Ministry of Higher Education, Scientific Research and Professional Training, Morocco; Nederlandse organisatie voor Wetenschappelijk Onderzoek (NWO), the Netherlands; The National Science Centre, Poland (2015/18/E/ST2/00758); National Authority for Scientific Research (ANCS), Romania; Ministerio de Ciencia, Innovacion, Investigacion y Universidades (MCIU): Programa Estatal de Generacion de Conocimiento (refs. PGC2018-096663-B-C41, -A-C42, -B-C43, -B-C44) (MCIU/FEDER), Severo Ochoa Centre of Excellence and MultiDark Consolider (MCIU), Junta de Andalucia (ref. SOMM17/6104/UGR), Generalitat Valenciana: Grisolia (ref. GRISOLIA/2018/119) and GenT (ref. CIDEGENT/2018/034) programs, La Caixa Foundation (ref. LCF/BQ/IN17/11620019), EU: MSC program (ref. 713673), Spain.The KM3NeT research infrastructure is currently under construction at two locations in the Mediterranean Sea. The KM3NeT/ORCA water-Cherenkov neutrino detector off the French coast will instrument several megatons of seawater with photosensors. Its main objective is the determination of the neutrino mass ordering. This work aims at demonstrating the general applicability of deep convolutional neural networks to neutrino telescopes, using simulated datasets for the KM3NeT/ORCA detector as an example. To this end, the networks are employed to achieve reconstruction and classification tasks that constitute an alternative to the analysis pipeline presented for KM3NeT/ORCA in the KM3NeT Letter of Intent. They are used to infer event reconstruction estimates for the energy, the direction, and the interaction point of incident neutrinos. The spatial distribution of Cherenkov light generated by charged particles induced in neutrino interactions is classified as shower- or track-like, and the main background processes associated with the detection of atmospheric neutrinos are recognized. Performance comparisons to machine-learning classification and maximum-likelihood reconstruction algorithms previously developed for KM3NeT/ORCA are provided. It is shown that this application of deep convolutional neural networks to simulated datasets for a large-volume neutrino telescope yields competitive reconstruction results and performance improvements with respect to classical approaches.French National Research Agency (ANR)
ANR-15-CE31-0020Centre National de la Recherche Scientifique (CNRS), Commission Europeenne (FEDER fund)European Union (EU)Institut Universitaire de France (IUF)LabEx UnivEarthS
ANR-10-LABX-0023
ANR-18-IDEX-0001Shota Rustaveli National Science Foundation of Georgia
FR-18-1268German Research Foundation (DFG)Greek Ministry of Development-GSRTIstituto Nazionale di Fisica Nucleare (INFN)Ministry of Education, Universities and Research (MIUR)
Research Projects of National Relevance (PRIN)Ministry of Higher Education, Scientific Research and Professional Training, MoroccoNetherlands Organization for Scientific Research (NWO)National Science Centre, Poland
2015/18/E/ST2/00758National Authority for Scientific Research (ANCS), RomaniaMinisterio de Ciencia, Innovacion, Investigacion y Universidades
PGC2018-096663-B-C41
A-C42
B-C43
B-C44Severo Ochoa Centre of ExcellenceJunta de Andalucia
SOMM17/6104/UGRGeneralitat Valenciana: Grisolia
GRISOLIA/2018/119
CIDEGENT/2018/034La Caixa Foundation
LCF/BQ/IN17/11620019EU: MSC program
71367
gSeaGen: The KM3NeT GENIE-based code for neutrino telescopes
Program summary
Program Title: gSeaGen
CPC Library link to program files: http://dx.doi.org/10.17632/ymgxvy2br4.1
Licensing provisions: GPLv3
Programming language: C++
External routines/libraries: GENIE [1] and its external dependencies. Linkable to MUSIC [2] and PROPOSAL
[3].
Nature of problem: Development of a code to generate detectable events in neutrino telescopes, using
modern and maintained neutrino interaction simulation libraries which include the state-of-the-art
physics models. The default application is the simulation of neutrino interactions within KM3NeT [4].
Solution method: Neutrino interactions are simulated using GENIE, a modern framework for Monte
Carlo event generators. The GENIE framework, used by nearly all modern neutrino experiments, is
considered as a reference code within the neutrino community.
Additional comments including restrictions and unusual features: The code was tested with GENIE version
2.12.10 and it is linkable with release series 3. Presently valid up to 5 TeV. This limitation is not intrinsic
to the code but due to the present GENIE valid energy range.
References:
[1] C. Andreopoulos at al., Nucl. Instrum. Meth. A614 (2010) 87.
[2] P. Antonioli et al., Astropart. Phys. 7 (1997) 357.
[3] J. H. Koehne et al., Comput. Phys. Commun. 184 (2013) 2070.
[4] S. Adrián-Martínez et al., J. Phys. G: Nucl. Part. Phys. 43 (2016) 084001.The gSeaGen code is a GENIE-based application developed to efficiently generate high statistics samples
of events, induced by neutrino interactions, detectable in a neutrino telescope. The gSeaGen code is able
to generate events induced by all neutrino flavours, considering topological differences between tracktype
and shower-like events. Neutrino interactions are simulated taking into account the density and
the composition of the media surrounding the detector. The main features of gSeaGen are presented
together with some examples of its application within the KM3NeT project.French National Research Agency (ANR)
ANR-15-CE31-0020Centre National de la Recherche Scientifique (CNRS)European Union (EU)Institut Universitaire de France (IUF), FranceIdEx program, FranceUnivEarthS Labex program at Sorbonne Paris Cite
ANR-10-LABX-0023
ANR-11-IDEX-000502Paris Ile-de-France Region, FranceShota Rustaveli National Science Foundation of Georgia (SRNSFG), Georgia
FR-18-1268German Research Foundation (DFG)Greek Ministry of Development-GSRTIstituto Nazionale di Fisica Nucleare (INFN)Ministry of Education, Universities and Research (MIUR)PRIN 2017 program Italy
NAT-NET 2017W4HA7SMinistry of Higher Education, Scientific Research and Professional Training, MoroccoNetherlands Organization for Scientific Research (NWO)
Netherlands GovernmentNational Science Centre, Poland
2015/18/E/ST2/00758National Authority for Scientific Research (ANCS), RomaniaMinisterio de Ciencia, Innovacion, Investigacion y Universidades (MCIU): Programa Estatal de Generacion de Conocimiento, Spain (MCIU/FEDER)
PGC2018-096663-B-C41
PGC2018-096663-A-C42
PGC2018-096663-BC43
PGC2018-096663-B-C44Severo Ochoa Centre of Excellence and MultiDark Consolider (MCIU), Junta de Andalucia, Spain
SOMM17/6104/UGRGeneralitat Valenciana: Grisolia, Spain
GRISOLIA/2018/119GenT, Spain
CIDEGENT/2018/034La Caixa Foundation
LCF/BQ/IN17/11620019EU: MSC program, Spain
71367
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