Hasil untuk "Atomic physics. Constitution and properties of matter"

Jiaheng Li, Quansheng Wu, Hongming Weng

Abstract Quantum anomalous Hall (QAH) insulators are characterized by vanishing longitudinal resistance and quantized Hall resistance in the absence of an external magnetic field. Among them, high-Chern-number QAH insulators offer multiple nondissipative current channels, making them crucial for the development of low-power-consumption electronics. Using first-principles calculations, we propose that high-Chern-number (C > 1) QAH insulators can be realized in MnBi2Te4 (MBT) multilayer films through the combination of mixed stacking orders, eliminating the need for additional buffer layers. The underlying physical mechanism is validated by calculating real-space-resolved anomalous Hall conductivity (AHC). Local AHC is found to be predominantly located in regions with consecutive correct stacking orders, contributing to quasi-quantized AHC. Conversely, regions with consecutive incorrect stacking contribute minimally to the total AHC, which can be attributed to the varied interlayer coupling in different stacking configurations. Our work provides valuable insights into the design principle for achieving large Chern numbers, and highlights the role of stacking configurations in manipulating electronic and topological properties in MBT films and its derivatives.

V. V. Zhuk, O. M. Mikheev, L. G. Ovsyannikova

The effect of X-ray irradiation of pea seeds at a dose of 20 Gy on the endurance of pea plants to UV-C irradiation at a dose of 5 kJ/m2 was studied. It was shown that X-ray irradiation of seeds stimulated plant growth, reduced the effect of UV-C on the plants grown, pigment complex of leaves, stimulated its recovery, and accelerated the utilization of excess H2O2 in leaves. It was shown that the effect of X-rays on pea seeds significantly reduced the destructive effect of high-energy ultraviolet radiation on pea plants. Irradiation of dry pea seeds with X-rays stimulated defense mechanisms that increased the resistance of plants to UV-C.

Junde Liu, Pei Liu, Liu Yang et al.

Abstract Nonvolatile optical manipulation of material properties on demand is a highly sought-after feature in the advancement of future optoelectronic applications. Here, we unravel the nature of the single-laser-pulse induced hidden state in 1T-TaS2 by systematically investigating the electronic structure evolution and the pulse-pair control throughout the reversible transition cycle. Our data indicate a mixed-stacking state involving two similarly low-energy interlayer orders, which is manifested as the charge density wave phase disruption. Furthermore, we elucidate distinct mechanisms underlying the bidirectional transformations — the ultrafast formation of the hidden state is initiated by a coherent phonon which triggers a competition between interlayer stacking orders, while its recovery is governed by the progressive domain evolution. Our work highlights the deterministic role of the competing interlayer orders in the nonvolatile phase transition in 1T-TaS2, establishing all-optical engineering of stacking orders in low-dimensional materials as a viable strategy for achieving desirable nonvolatile electronic devices.

Andrea León, Carmine Autieri, Thomas Brumme et al.

Abstract The interplay of strong electronic correlations, sizable octahedral distortions, and pronounced spin-orbit coupling (SOC) makes perovskite oxides promising candidates for realizing altermagnetic phases. We study altermagnetic phases in Ca3Ru2O7, a non-centrosymmetric layered perovskite whose ground state is a Kramers-degenerate antiferromagnet. We show that an alternative Néel-type spin arrangement hosts a P-2 d-wave altermagnetic state with orbital selectivity similar to Ca2RuO4. Including SOC generates a symmetry-allowed p-wave component and yields a hybrid d/p-wave altermagnetic order. We further demonstrate that biaxial strain tunes both magnetic stability and band splitting: compressive strain beyond 2% favors the altermagnetic phase over the antiferromagnetic ground state, while tensile strain increases altermagnetic splittings by up to 9%. To quantify these trends, we define an altermagnetic figure of merit and trace its strain dependence to changes in electronic localization and octahedral geometry in this polar metal.

Benedikt M. Reible, Ana Djurdjevac, Luigi Delle Site

Despite their simplicity, quantum harmonic oscillators are ubiquitous in the modeling of physical systems. They are able to capture universal properties that serve as references for the more complex systems found in nature. In this spirit, we apply a model of a Hamiltonian for open quantum systems in equilibrium with a particle reservoir to ensembles of quantum oscillators. By treating (i) a dilute gas of vibrating particles and (ii) a chain of coupled oscillators as showcases, we demonstrate that the property of varying numbers of particles leads to a mandatory condition on the energy of the system. In particular, the chemical potential plays the role of a parameter of control that can externally manipulate the spectrum of a system and the corresponding accessible quantum states.

Omshankar, Vivek Venkataraman, Joyee Ghosh

Polarization-entangled photon-based quantum key distribution (QKD) has seen notable advancements, requiring users to share a common frame of reference that might lead to a significant technical overhead of constant monitoring of their frame of reference. In this work, we characterize and demonstrate hybrid entangled photon pairs for their utilization in rotational alignment-free QKD applications. By employing vortex half-wave retarders that have an azimuthally varying fast axis with a topological charge of q=12, we generate high brightness rotationally invariant hybrid entangled photons and show their resilience against the misalignment of the frame of reference. We demonstrate high fidelity (>92%) entanglement and depict a low quantum bit error rate (QBER) of ∼5−6% (lower than the threshold value of 11%) at a significantly high angle of misalignment θ>45°), in contrast to the polarization-entangled photon pairs that suffer from the degradation of entanglement quality due to a rotational misalignment between the reference frame of communicating entities. The rotationally invariant hybrid photon pairs with robust entanglement properties offer a significant advantage for secure and reliable quantum communication, making them lucrative candidates for applications such as satellite-to-satellite and ground-to-satellite QKD networks. We also show the reliability and stability of the entangled photon source over a long period (measured over 6 h) by demonstrating the BBM92 protocol with a raw key rate of ∼2.8 kbps and a QBER of ∼5% in a single-pass configuration. The performance metrics of our quantum source, measured with conventional avalanche photodiodes (SPADs, quantum efficiency ∼60%, dark counts ∼40 cps), are among the best values reported so far with these detectors.

Eduardo Marin-Bujedo, Julien A. L. Grondin, Thomas Schiltz et al.

We report the construction and characterization of an experimental setup for producing a cold gas of $^{40}$Ca atoms and excite them to high Rydberg states with a resonant three-photon-excitation scheme. The apparatus comprises four stages, each designed in-house. An oven heated to $\sim 500^\circ$C generates an atomic beam that is collimated by a capillary stack. The beam is sent into a passive, permanent-magnet-based Zeeman slower that reduces the atomic velocity to $30$ m/s. The slow atoms are captured in a magneto-optical trap (MOT) and cooled to $1.0(3)$ mK with a trapping time of $16(2)$ ms. Ground-state atoms in the cold gas are excited to high Rydberg states via resonant excitation through the intermediate $4s4p\, ^1P_1$ and $4s4d\, ^1D_2$ states. The MOT is operated at the center of an electrode stack, which serves to apply continuous and pulsed electric fields and field-ionize the Rydberg atoms for detection. We benchmark our MOT against previous implementations and find its performance consistent with state-of-the-art results in terms of temperature and trapping lifetime. Finally, we demonstrate Rydberg spectroscopy of calcium, confirming the system's suitability for ultracold Rydberg physics experiments.

P. S. Bhupal Dev

The burgeoning field of multi-messenger astronomy is poised to revolutionize our understanding of the most enigmatic astrophysical phenomena in the Universe. At the same time, it has opened a new window of opportunity to probe various particle physics phenomena. This is illustrated here with a few example new physics scenarios, namely, decaying heavy dark matter, pseudo-Dirac neutrinos and light dark sector physics, for which new constraints are derived using recent multi-messenger observations.

Pedro H. Alvarez, Farhan T. Chowdhury, Luke D. Smith et al.

Understanding the intricate quantum spin dynamics of radical pair reactions is crucial for unraveling the underlying nature of chemical processes across diverse scientific domains. In this work, we leverage Trotterization to map coherent radical pair spin dynamics onto a digital gate-based quantum simulation. Our results demonstrated an agreement between the idealized noiseless quantum circuit simulations and established master equation approaches for homogeneous radical pair recombination, identifying ∼15 Trotter steps to be sufficient for faithfully reproducing the coupled spin dynamics of a prototypical system. By utilizing this computational technique to study the dynamics of spin systems of biological relevance, our findings underscore the potential of digital quantum simulation (DQS) of complex radical pair reactions and builds the groundwork toward more utilitarian investigations into their intricate reaction dynamics. We further investigate the effect of realistic error models on our DQS approach and provide an upper limit for the number of Trotter steps that can currently be applied in the absence of error mitigation techniques before losing simulation accuracy to deleterious noise effects.

Bilalodin, A. Haryadi, Sehah et al.

A microdosimetry test on a double layer beam shaping assembly (DLBSA) neutron beam has been carried out using the particle and heavy ion transport code system (PHITS). The test aims to understand the mechanism of interactions between neutrons and microcells and to determine the linear energy transfer (LET) and the relative biological effectiveness (RBE) values of the DLBSA neutron beam. The test was carried out by interacting a neutron beam with microcells containing 10B using a boron concentration of 70 ppm. The neutron source used comes from a 30 MeV cyclotron-based DLBSA. The simulation results show that the interaction of neutrons with microcells occurs through scattering, reflection, and absorption reaction mechanisms. The results of the microdosimetry test showed that the peak LET value of α-particles was 100 keV/μm and 7Li was 200 keV/μm, with an RBE value for α of 9.83 and 7Li of 6.11.

O. V. Mykhailov, A. O. Doroshenko, M. V. Saveliev

The results of the analysis of temperature monitoring data were obtained using the information and measuring system (IMS) "Finish" (1991 - 2015) and expert research system, new safe confinement (NSC) integrated control system in the main volume (MV) under the arched space, and the weather station in Chornobyl (1991 - 2023). After the NSC was installed in the design position, a slight increase in average annual MV NSC air temperature was observed before 2021. During the same period, the average annual temperature of concrete around the localization area of nuclearly hazardous clusters of fuel-containing materials (FCM NHC) in room 305/2 of the "Shelter" object increased by 1.3 - 1.4 times and had returned to 0.7 - 0.8 of the value of 1991. From 2021, no next increase in the mean annual temperature of concrete has been noticed. As of 2023, if compared to the monitoring period before Arch pushed into its design position, the calendar shift between the temperature of concrete and the surrounding environment enhanced to 1 month, according to both minimum and maximum average month values.

Søren Engelberth Hansen, Guillermo Arregui, Ali Nawaz Babar et al.

The scalability of integrated photonics hinges on low-loss chip-scale components, which are important for classical applications and crucial in the quantum domain. An important component is the power splitter, which is an essential building block for interferometric devices. Here, we use inverse design by topology optimization to devise a generic design framework for developing power splitters in any material platform, although we focus the present work on silicon photonics. We report on the design, fabrication, and characterization of silicon power splitters and explore varying domain sizes and wavelength spans around a center wavelength of 1550 nm. This results in a set of power splitters tailored for ridge, suspended, and embedded silicon waveguides with an emphasis on compact size and wide bandwidths. The resulting designs have a footprint of $2\,\mu\textrm{m}\times3\,\mu\textrm{m}$ and exhibit remarkable 0.5 dB bandwidths exceeding 300 nm for the ridge and suspended power splitters and 600 nm for the embedded power splitter. We fabricate the power splitters in suspended silicon circuits and characterize the resulting devices using a cutback method. The experiments confirm the low excess loss, and we measure a 0.5 dB bandwidth of at least 245 nm—limited by the wavelength range of our lasers.

V. A. Dzuba, V. V. Flambaum, A. J. Mansour

The aim of this paper is to derive limits on various forms of ``new physics'' using atomic experimental data. Interactions with dark energy and dark matter fields can lead to space-time variations of fundamental constants, which can be detected through atomic spectroscopy. In this study, we examine the effects of a varying nuclear mass $m_{N}$ and nuclear radius $r_{N}$ on two transition ratios: the comparison of the two-photon transition in atomic hydrogen with the hyperfine transition in $^{133}$Cs based clocks, and the ratio of optical clock frequencies in in Al$^{+}$ and Hg$^{+}$. The sensitivity of these frequency ratios to changes in $m_{N}$ and $r_{N}$ enables us to derive new limits on the variations of the proton mass, quark mass, and the QCD parameter $θ$. Additionally, we consider the scalar field generated by the Yukawa-type interaction of feebly interacting hypothetical scalar particles with Standard Model particles in the presence of massive bodies such as the Sun and Moon. Using the data from the Al$^{+}$/Hg$^{+}$, Yb$^{+}$/Cs and Yb$^{+}$(E2)/Yb$^{+}$(E3) transition frequency ratios, we place constraints on the interaction of the scalar field with photons, nucleons, and electrons for a range of scalar particle masses. We also investigate limits on the Einstein Equivalence Principle (EEP) violating term ($c_{00}$) in the Standard Model Extension (SME) Lagrangian and the dependence of fundamental constants on gravity.

Uddipta Kar, Akhilesh Kr. Singh, Yu-Te Hsu et al.

Abstract In a thin Weyl semimetal, a thickness dependent Weyl-orbit quantum oscillation was proposed to exist, originating from a nonlocal cyclotron orbit via electron tunnelings between top and bottom Fermi-arc surface states. Here, magneto-transport measurements were carried out on untwinned Weyl metal SrRuO3 thin films. In particular, quantum oscillations with a frequency F s1 ≈ 30 T were identified, corresponding to a small Fermi pocket with a light effective mass. Its oscillation amplitude appears to be at maximum for thicknesses in a range of 10 to 20 nm, and the phase of oscillation exhibits a systematic change with film thickness. The constructed Landau fan diagram shows an unusual concave downward curvature in the 1/μ 0 H n -n curve, where n is the Landau level index. From thickness and field-orientation dependence, the F s1 oscillation is attributed to be of surface origin. Those findings can be understood within the framework of the Weyl-orbit quantum oscillation effect with non-adiabatic corrections.

Sonia Haddad, Gihan Kamel, Lalla Btissam Drissi et al.

Various panel sessions were organized to highlight the activities of the African Strategy for Fundamental and Applied Physics (ASFAP) Working Groups during the second African Conference of Fundamental and Applied Physics (ACP2021) that was held in March 7-11, 2022. A joint session was devoted to highlight the activities assigned to the Light Sources, Accelerators, Biophysics, Earth Sciences, Atomic and Molecular Physics, and Condensed Matter and Materials Physics Working Groups. Major outcomes and recommendations are demonstrated and deliberated in this contribution.

Jürg Fröhlich

This paper begins with a summary of a powerful formalism for the study of electronic states in condensed matter physics called "Gauge Theory of States/Phases of Matter." The chiral anomaly, which plays quite a prominent role in that formalism, is recalled. I then sketch an application of the chiral anomaly in 1+1 dimensions to quantum wires. Subsequently, some elements of the quantum Hall effect in two-dimensional (2D) gapped ("incompressible") electron liquids are reviewed. In particular, I discuss the role of anomalous chiral edge currents and of anomaly inflow in 2D gapped electron liquids with explicitly or spontaneously broken time reversal, i.e., in Hall- and Chern insulators. The topological Chern-Simons action yielding the transport equations valid in the bulk of such systems and the associated anomalous edge action are derived. The results of a general classification of "abelian" Hall insulators are outlined. After some remarks on induced Chern-Simons actions, I sketch results on certain 2D chiral photonic wave guides. I then continue with an analysis of chiral edge spin-currents and the bulk response equations in time-reversal invariant 2D topological insulators of electron gases with spin-orbit interactions. The "chiral magnetic effect" in 3D systems and axion-electrodynamics are reviewed next. This prepares the ground for an outline of a general theory of 3D topological insulators, including "axionic insulators". Some remarks on Weyl semi-metals, which exhibit the chiral magnetic effect, and on Mott transitions in 3D systems with dynamical axion-like degrees of freedom conclude this review.}

MAISON CLOUATRE, MOHAMMAD JAVAD KHOJASTEH, MOE Z. WIN

This article proposes an end-to-end framework for the learning-enabled control of closed quantum systems. The proposed learning technique is the first of its kind to utilize a hierarchical design, which layers probing control, quantum state tomography, quantum process tomography, and Hamiltonian learning to identify both the internal and control Hamiltonians. Within this context, a novel quantum process tomography algorithm is presented, which involves optimization on the unitary group, i.e., the space of unitary operators, to ensure physically meaningful predictions. Our scalable Hamiltonian learning algorithms have low memory requirements and tunable computational complexity. Once the Hamiltonians are learned, we formalize data-driven model-predictive quantum control (MPQC). This technique utilizes the learned model to compute quantum control parameters in a closed-loop simulation. Then, the optimized control input is given to a physical quantum system in an open-loop fashion. Simulations show model-predictive quantum control to be more efficient than the current state-of-the-art, quantum optimal control, when sequential quadratic programming (SQP) is used to solve each control problem.

M. N. Shneider, V. V. Semak

A theoretical model that describes a new mechanism of atomic and molecular ionization in a low intensity electro-magnetic wave (light or laser beam) with the energy of quanta that is lower than required for a single photon ionization is presented. The essence of the proposed physical mechanism is the step-like gain of energy of a bound electron that occurs every time the phase of the electro-magnetic field jolts. Providing there is sufficiently large number of the phase jolts, the summation of the step increases of the electron oscillation energy can render the total energy of the bound electron such that it exceeds the ionization potential.

Matthias Meister, Albert Roura

Mixtures of ultracold quantum gases are at the heart of high-precision quantum tests of the weak equivalence principle, where extremely low expansion rates have to be reached with matter-wave lensing techniques. We propose to simplify this challenging atom-source preparation by employing magic laser wavelengths for the optical lensing potentials which guarantee that all atomic species follow identical trajectories and experience common expansion dynamics. In this way, the relative shape of the mixture is conserved during the entire evolution while cutting in half the number of required lensing pulses compared to standard approaches.

Haibiao Zhou, Qiyuan Feng, Yubin Hou et al.

Abstract The CE phase is an extraordinary phase exhibiting the simultaneous spin, charge, and orbital ordering due to strong electron correlation. It is an ideal platform to investigate the role of the multiple orderings in the phase transitions and discover emergent properties. Here, we use a cryogenic high-field magnetic force microscope to image the phase transitions and properties of the CE phase in a Pr0.5Ca0.5MnO3 thin film. In a high magnetic field, we observed a clear suppression of magnetic susceptibility at the charge-ordering insulator transition temperature (T COI), whereas, at the Néel temperature (T N), no significant change is observed. This observation favors the scenario of strong antiferromagnetic correlation developed below T COI but raises questions about the Zener polaron paramagnetic phase picture. Besides, we discoverd a phase-separated surface state in the CE phase regime. Ferromagnetic phase domains residing at the surface already exist in zero magnetic field and show ultra-high magnetic anisotropy. Our results provide microscopic insights into the unconventional spin- and charge-ordering transitions and revealed essential attributes of the CE phase, highlighting unusual behaviors when multiple electronic orderings are involved.