Search

Reconstructed tracks of muons produced in neutrino interactions provide the precise probe for the neutrino direction. Therefore, track-like events are a powerful tool to search for neutrino point sources. Recently, Baikal-GVD has demonstrated the first sample of low-energy neutrino candidate events extracted from the data of the season 2019 in a so-called single-cluster analysis - treating each cluster as an independent detector. In this paper, the extension of the track-like event analysis to a wider data set is discussed and the first high-energy track-like events are demonstrated. The status of multi-cluster track reconstruction and that of the event analysis are also discussed., Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023)

Baikal-GVD (Gigaton Volume Detector) is a neutrino telescope installed at a depth of 1366 m in Lake Baikal. The expedition of 2023 brought the number of optical modules in the array up to 3492 (including experimental strings). These optical modules detect the Cherenkov radiation from secondary charged particles coming from the neutrino interactions. Neutrinos produce different kinds of topologically distinct light signatures. Charged current muon neutrino interactions create an elongated track in the water. Charged and neutral current interactions of other neutrino flavors yield hadronic and electromagnetic cascades. The background in the neutrino cascade channel arises mainly due to discrete stochastic energy losses produced along atmospheric muon tracks. In this paper, a developed algorithm for the cascade event selection is presented., Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023)

Baikal Gigaton Volume Detector is a cubic kilometer scale neutrino telescope under construction in Lake Baikal. As of July 2023, Baikal-GVD consists of 96 fully deployed strings resulting in 3456 optical modules installed. The observation of neutrinos is based on detection of Cherenkov radiation emitted by the products of neutrino interactions. In this contribution, description of the double cascade reconstruction technique as well as evaluation of precision of this algorithm is given., Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023)

The deployment of the Baikal-GVD deep underwater neutrino telescope is in progress now. About 3500 deep underwater photodetectors (optical modules) arranged into 12 clusters are operating in Lake Baikal. For increasing the efficiency of cascade-like neutrino event detection, the telescope deployment scheme was slightly changed. Namely, the inter-cluster distance was reduced for the newly deployed clusters and additional string of optical modules are added between the clusters. The first inter-cluster string was installed in 2022 and two such strings were installed in 2023. This paper presents a Monte Carlo estimate of the impact of these configuration changes on the cascade detection efficiency as well as technical implementation and results of in-situ tests of the inter-cluster strings., Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023)

Baikal-GVD is a next generation, kilometer-scale neutrino telescope currently under construction in Lake Baikal. GVD consists of multi-megaton subarrays (clusters) and is designed for the detection of astrophysical neutrino fluxes at energies from a few TeV up to 100 PeV. The large detector volume and modular design of Baikal-GVD allows for the measurements of the astrophysical diffuse neutrino flux to be performed already at early phases of the array construction. We present here recent results of the measurements on the diffuse cosmic neutrino flux obtained with the Baikal-GVD neutrino telescope using cascade-like events., Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023)

The Baikal-GVD is a deep-underwater neutrino telescope being constructed in Lake Baikal. After the winter 2023 deployment campaign the detector consists of 3456 optical modules installed on 96 vertical strings. The status of the detector and progress in data analysis are discussed in present report. The Baikal-GVD data collected in 2018-2022 indicate the presence of cosmic neutrino flux in high-energy cascade events consistent with observations by the IceCube neutrino telescope. Analysis of track-like events results in identification of first high-energy muon neutrino candidates. These and other results from 2018-2022 data samples are reviewed in this report.

We present the results of the two-year (2021-2022) monitoring of absorption and scattering lengths of light with wavelength 400-620 nm within the effective volume of the deep underwater neutrino telescope Baikal-GVD, which were measured by a device Baikal-5D No.2. The Baikal-5D No.2. was installed during the 2021 winter expedition at a depth of 1180 m. The absorption and scattering lengths were measured every week in 9 spectral points. The device Baikal-5D No.2 also has the ability to measure detailed scattering and absorption spectra. The data obtained make it possible to estimate the range of changes in the absorption and scattering lengths over a sufficiently long period of time and to investigate the relationship between the processes of changes in absorption and scattering. An analysis was made of changes in absorption and scattering spectra for the period 2021-2022.

The Baikal-GVD neutrino detector is a deep-underwater neutrino telescope under construction and recently after the winter 2023 deployment it consists of 3456 optical modules attached on 96 vertical strings. This 3-dimensional array of photo-sensors allows to observe ambient light in the vicinity of the Baikal-GVD telescope that is associated mostly with water luminescence. Results on time and space variations of the luminescent activity are reviewed based on data collected in 2018-2022.

We present a new procedure for time calibration of the Baikal-GVD neutrino telescope. The track reconstruction quality depends on accurate measurements of arrival times of Cherenkov photons. Therefore, it is crucial to achieve a high precision in time calibration. For that purpose, in addition to other calibration methods, we employ a new procedure using atmospheric muons reconstructed in a single-cluster mode. The method is based on iterative determination of effective time offsets for each optical module. This paper focuses on the results of the iterative reconstruction procedure with time offsets from the previous iteration and the verification of the method developed. The theoretical muon calibration precision is estimated to be around 1.5-1.6ns., Comment: 38th International Cosmic Ray Conference (ICRC2023)

The Baikal-GVD alert system was launched at the beginning of 2021. There are alerts for muon neutrinos (long upward-going track-like events) and all-flavour neutrinos (high-energy cascades). The system is able to get a preliminary response to external alerts with a temporal delay of about 3-10 minutes. The Baikal-GVD data processing and the results of the follow-up procedure are described. We report on the analysis of the coincidence in time and direction between the Baikal-GVD cascade GVD20211208CA with an estimated energy of 43 TeV and the announced alert IceCube211208A possibly associated with a flaring state of the blazar PKS 0735+178., Comment: 9 pages, 5 figures

We report on the observation of a rare neutrino event detected by Baikal-GVD in April 2021. The event GVD210418CA is the highest-energy cascade observed by Baikal-GVD so far from the direction below the horizon. The estimated cascade energy is $224\pm75$~TeV. The evaluated signalness parameter of GVD210418CA is 97.1\% using an assumption of the E$^{-2.46}$ spectrum of astrophysical neutrinos. The arrival direction of GVD210418CA is near the position of the well-known radio blazar TXS~0506+056, with the angular distance being within a 90\% directional uncertainty region of the Baikal-GVD measurement. The event was followed by a radio flare observed by the RATAN-600 radio telescope, further strengthening the case for the neutrino-blazar association., Comment: 9 pages, 6 figures, Contribution to the 38th International Cosmic Rays Conference (ICRC2023). arXiv admin note: text overlap with arXiv:2210.01650

We analyze the origin of the parabolic background of magnetoresistance oscillations measured in finite-width superconducting mesoscopic rings with input and output stubs and in patterned films. The transmission model explaining the sinusoidal oscillation of magnetoresistance is extended to address the parabolic background as a function of the magnetic field. Apart from the interference mechanism activated by the ring, pinned superconducting vortices as topological defects introduce a further interference-based distribution of supercurrents that affects, in turn, the voltmeter-sensed quasiparticles. The onset of vortices changes the topology of the superconducting state in a mesoscopic ring in a such a way that the full magnetoresistance dynamics can be interpreted owing to the interference of the constituents of the order parameter induced by both the ring with its doubly-connected topology and the vortex lattice in it., Comment: 15 pages, 6 figures

The Ginzburg-Landau theory is used to model the order parameter of a finite-size mesoscopic ring to investigate the effects of the onset of screening currents on the transport of incoming ones. The magnetic flux breaks the symmetry of currents between input and output stubs by means of an induced spatial ordering upon diamagnetic and paramagnetic supercurrents circulating in the ring. The distribution of those screening currents drives the interference of incoming/outgoing supercurrents resulting into a sinusoidal variation of resistance as a function of the magnetic flux even if the density of quasiparticles is not modified by the external magnetic field.

Thermal transport in the Si/SiO$_2$ multishell nanotubes is investigated theoretically. The phonon energy spectra are obtained using the atomistic Lattice Dynamics approach. Thermal conductivity is calculated using the Boltzmann transport equation within the relaxation time approximation. Redistribution of the vibrational spectra in multishell nanotubes leads to a decrease of the phonon group velocity and the thermal conductivity as compared to homogeneous Si nanowires. Phonon scattering on the Si/SiO$_2$ interfaces is another key factor of strong reduction of the thermal conductivity in these structures (down to 0.2 W/mK at room temperature). We demonstrate that phonon thermal transport in Si/SiO$_2$ nanotubes can be efficiently suppressed by a proper choice of nanotube's geometrical parameters: lateral cross-section, thickness and number of shells., Comment: 14 pages, 4 figures

Under a strong transport current, the induced voltage in superconductor nanomembranes in a magnetic field with submicron inhomogeneity shows a pulse on a certain interval of the magnetic field. It is a manifestation of a wide phase-slip domain. The topological transition accompanying the phase-slip effect consists in the occurrence of two new loops of weak superconducting currents connecting two regions of superconducting screening currents, which are disconnected in case of vortex-chain dynamics. In the middle of the phase-slip domain, rapid dynamics of the superconducting order parameter consists in decoupling of a spontaneously nucleated vortex-antivortex pair, subsequent motion of a vortex and an antivortex in the opposite directions followed by their annihilation with an antivortex and a vortex from the adjacent pairs. The submicron-scale inhomogeneity of the magnetic field can be achieved through a direct patterning of the magnetic field applied to a planar membrane or using advanced nanostructuring, such as roll-up technology, focused ion-beam deposition or coating carbon nanotubes by superconducting materials. If the applied magnetic field is orthogonal to the axis of a microtube, which carries transport current in the azimuthal direction, the phase-slip regime is characterized by the vortex-antivortex lifetime of 10E-15 s versus 10E-12 s for disconnected vortex dynamics in the half-tubes. The phase-slip dynamics determines the voltage-magnetic field and voltage-current characteristics in nanoarchitectures with multiple disconnected loops of superconducting screening currents.

An inhomogeneous transport current, which is introduced through multiple electrodes in an open Nb microtube, is shown to lead to a controllable branching of the vortex nucleation period. The detailed mechanism of this branching is analyzed using the time-dependent Ginzburg-Landau equation. The relative change of the vortex nucleation period strongly depends on the geometry of multiple electrodes. The average number of vortices occurring in the tube in a nanosecond can be effectively reduced owing to the inhomogeneous transport current, what is important for noise and energy dissipation reduction in superconductor applications, e.g., for an extension of the operation regime of superconductor-based sensors to lower frequencies., Comment: 8 pages, 4 figures

In-plane polarized light experiences a non-trivial topological evolution as it propagates resonantly in a M\"obius ring resonator. The resultant geometric phase varies continuously when changing the light ellipticity, which leads to constructive interference for a non-integer number of wavelengths, and therefore to the occurrence of an arbitrary fractional number of optical modes. The geometric phase in M\"obius-ring resonators is topologically robust and implies excellent intrinsic fault-tolerance., Comment: This paper has been withdrawn by the authors due to a missing of a unified opinion

A procedure to construct $K$-matrices from the generalized $q$-Onsager algebra $\cO_{q}(\hat{g})$ is proposed. This procedure extends the intertwiner techniques used to obtain scalar (c-number) solutions of the reflection equation to dynamical (non-c-number) solutions. It shows the relation between soliton non-preserving reflection equations or twisted reflection equations and the generalized $q$-Onsager algebras. These dynamical $K$-matrices are important to quantum integrable models with extra degrees of freedom located at the boundaries: for instance, in the quantum affine Toda field theories on the half-line they yield the boundary amplitudes. As examples, the cases of $\cO_{q}(a^{(2)}_{2})$ and $\cO_{q}(a^{(1)}_{2})$ are treated in details.

We analyze the applicability of the Rosenfeld entropy scaling relations to the systems with the core-softened potentials demonstrating the water-like anomalies. It is shown that the validity of the of Rosenfeld scaling relation for the diffusion coefficient depends on the thermodynamic path which is used for the calculations of the kinetic coefficients and the excess entropy. In particular, it is valid along isochors, but it breaks down along isotherms., Comment: 4 pages, 6 figures

We compute the Bethe equations of generalized Hubbard models, and study their thermodynamical limit. We argue how they can be connected to the ones found in the context of AdS/CFT correspondence, in particular with the so-called dressing phase problem. We also show how the models can be interpreted, in condensed matter physics, as integrable multi-leg Hubbard models., Comment: 30 pages

We compute the eigenfunctions, energies and Bethe equations for a class of generalized integrable Hubbard models based on gl(n|m)\oplus gl(2) superalgebras. The Bethe equations appear to be similar to the Hubbard model ones, up to a phase due to the integration of a subset of `simple' Bethe equations. We discuss relations with AdS/CFT correspondence, and with condensed matter physics., Comment: 36 pages

We have theoretically studied exciton states and photoluminescence spectra of strained wurtzite AlGaN/GaN quantum-well heterostructures. The electron and hole energy spectra are obtained by numerically solving the Schr\"odinger equation, both for a single-band Hamiltonian and for a non-symmetrical 6-band Hamiltonian. The deformation potential and spin-orbit interaction are taken into account. For increasing built-in field, generated by the piezoelectric polarization and by the spontaneous polarization, the energy of size quantization rises and the number of size quantized electron and hole levels in a quantum well decreases. The exciton energy spectrum is obtained using electron and hole wave functions and two-dimensional Coulomb wave functions as a basis. We have calculated the exciton oscillator strengths and identified the exciton states active in optical absorption. For different values of the Al content x, a quantitative interpretation, in a good agreement with experiment, is provided for (i) the red shift of the zero-phonon photoluminescence peaks for increasing the quantum-well width, (ii) the relative intensities of the zero-phonon and one-phonon photoluminescence peaks, found within the non-adiabatic approach, and (iii) the values of the photoluminescence decay time as a function of the quantum-well width., Comment: 32 pages, 9 figures

Polarized neutron reflectometry (PNR) provides evidence that nonlocal electrodynamics governs the magnetic field penetration in an extreme low-k superconductor. The sample is an indium film with a large elastic mean free path (11 mkm) deposited on a silicon oxide wafer. It is shown that PNR can resolve the difference between the reflected neutron spin asymmetries predicted by the local and nonlocal theories of superconductivity. The experimental data support the nonlocal theory, which predicts a nonmonotonic decay of the magnetic field., Comment: 5 pages, 4 figures, LaTex, corrected typos and figures

Taking into account the tetrahedral shape of a quantum dot quantum well (QDQW) when describing excitonic states, phonon modes and the exciton-phonon interaction in the structure, we obtain within a non-adiabatic approach a quantitative interpretation of the photoluminescence (PL) spectrum of a single CdS/HgS/CdS QDQW. We find that the exciton ground state in a tetrahedral QDQW is bright, in contrast to the dark ground state for a spherical QDQW., Comment: 4 pages, 2 figures

We analyze the influence of the characteristics of the STM-tip (applied voltage, tip radius) on the electroluminescence spectra from an STM-tip-induced quantum dot taking into account the many-body effects. We find that positions of electroluminescence peaks, attributed to the electron-hole recombination in the quantum dot, are very sensitive to the shape and size of the confinement potential as determined by the tip radius and the applied voltage. A critical value of the tip radius is found, at which the luminescence peak positions as a function of the tip radius manifest a transition from decreasing behavior for smaller radii to increasing behavior for larger radii. We find that this critical value of the tip radius is related to the confinement in the lateral and normal direction., Comment: 15 pages, 5 figures

One- and multi-phonon excitations of the single crystalline LaCoO3 were studied using Raman spectroscopy in the temperature region of 5 K - 300 K. First-order Raman spectra show a larger number of phonon modes than allowed for the rhombohedral structure. Additional phonon modes are interpreted in terms of activated modes due to lattice distortions, arising from the Jahn-Teller (JT) activity of the intermediate-spin (IS) state of Co3+ ions. In particular, the 608-cm-1 stretching-type mode shows anomalous behavior in peak energy and scattering intensity as a function of temperature. The anomalous temperature dependence of the second-order phonon excitations spectra is in accordance with the Franck-Condon mechanism that is characteristic for a JT orbital order., Comment: 11 pages, 9 figures, to be published in J. Low. Temp. Physics

The ground-state energy, the addition energies and the optical absorption spectra are derived for interacting polarons in parabolic quantum dots in three and two dimensions. A path integral formalism for identical particles is used in order to take into account the fermion statistics. The approach is applied to both closed-shell and open-shell systems of interacting polarons. Using a generalization of the Jensen-Feynman variational principle, the ground-state energy of a confined N-polaron system is analyzed as a function of N and of the electron-phonon coupling constant. As distinct from the few-electron systems without the electron-phonon interaction, three types of spin polarization are possible for the ground state of the few-polaron systems: (i) a spin-polarized state, (ii) a state where the spin is determined by Hund's rule, (iii) a state with the minimal possible spin. A transition from a state fulfilling Hund's rule, to a spin-polarized state occurs when decreasing the electron density. In the strong-coupling limit, the system of interacting polarons turns into a state with the minimal possible spin. These transitions should be experimentally observable in the optical absorption spectra of quantum dots., Comment: 33 pages, 9 figures, E-mail addresses: jozef.devreese@ua.ac.be, fons.brosens@ua.ac.be, vladimir.fomin@ua.ac.be, sergei.klimin@ua.ac.be, accepted for Phys. Rev. B