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

Chenjiang Qian, Viviana Villafañe, Martin Schalk et al.

A spectral anomaly exhibiting pronounced asymmetry is observed in the emission spectrum for nanocavities when they are pumped by the charged boron vacancy VB− and have a high Q-factor above a threshold of 10 000. In contrast, cavities without VB− centers always exhibit trivial Lorentzian emission. These observations are well explained by the feature of VB− that its light–matter interaction is induced by local phonon modes. Moreover, we find that in nanocavities the local phonon modes arise from the coupling between VB− lattice phonons and cavity mechanical modes, supported by the spatially resolved spectroscopy of VB− and resonant spectroscopy of the cavity photonic mode. Our results reveal a novel system involving the coupling in both the photonic and phononic degrees of freedom between the active material and the nanocavity. Such an emitter–optomechanical interaction system shows great potential in non-trivial quantum photonic devices and provides a platform to interface spin defects, photons, and phonons.

Jingwei Dong, Jiuxiang Zhang, Zailan Zhang et al.

Abstract Two-dimensional (2D) layered material grey arsenic exhibits great potential for electronic and optoelectronics devices. Identifying the orbital texture in the electronic energy bands close to Fermi level is crucial for understanding and further manipulating the optoelectronic properties of grey arsenic. In this work, we investigate the orbital properties from bulk-state and surface-state of grey arsenic by using multidimensional angle-resolved photoemission spectroscopy, under different light polarization and crystal orientation conditions. Furthermore, by combining the experimental results with first-principles calculations based on density functional theory (DFT), we reveal that both the surface and bulk states of grey arsenic contain 4 s, 4p x , 4p y and 4p z orbitals, but the orbital ratios are different. Our study offers new insight into the orbital nature of grey arsenic and also paves the way for investigation of orbital properties in other 2D materials.

Sebastian De Haro, Enrico Cinti

For more than half a century, dualities have been at the heart of modern physics. From quantum mechanics to statistical mechanics, condensed matter physics, quantum field theory and quantum gravity, dualities have proven useful in solving problems that are otherwise quite intractable. Being surprising and unexpected, dualities have been taken to raise philosophical questions about the nature and formulation of scientific theories, scientific realism, emergence, symmetries, explanation, understanding, and theory construction. This book discusses what dualities are, gives a selection of examples, explores the themes and roles that make dualities interesting, and highlights their most salient types. It aims to be an entry point into discussions of dualities in both physics and philosophy. The philosophical discussion emphasises three main topics: whether duals are theoretically equivalent, the view of scientific theories that is suggested by dualities (namely, a geometric view of theories), and the compatibility between duality and emergence.

Arvin Gopal Subramaniam, Sagarika Adhikary, Rajesh Singh

Coherent collective motion is a widely observed phenomenon in active matter systems. Here, we report a flocking transition mechanism in a system of chemically interacting active colloidal particles sustained purely by chemo-repulsive torques at low to medium densities. The basic requirements to maintain the global polar order are excluded volume repulsions and long-ranged repulsive torques. This mechanism requires that the time scale individual colloids move a unit length to be dominant with respect to the time they deterministically respond to chemical gradients, or equivalently, pair colloids sliding together a minimal unit length before deterministically rotating away from each other. Switching on the translational repulsive forces renders the flock a crystalline structure. Furthermore, liquid flocks are observed for a range of chemo-attractive inter-particle forces. Various properties of these two distinct flocking phases are contrasted and discussed. We complement these results with stability analysis of a hydrodynamic model, which admits the transition corresponding to destabilization of the flocking state observed in particle-based simulations.

Alexander N. Bourzutschky, Benjamin L. Lev, Jonathan Keeling

Abstract Phonon polaritons are hybrid states of light and matter that are typically realised when optically active phonons couple strongly to photons. We suggest a new approach to realising phonon polaritons, by employing a transverse-pumping Raman scheme, as used in experiments on cold atoms in optical cavities. This approach allows hybridisation between an optical cavity mode and any Raman-active phonon mode. Moreover, this approach enables one to tune the effective phonon–photon coupling by changing the strength of the transverse pumping light. We show that such a system may realise a phonon-polariton condensate. To do this, we find the stationary states and use Floquet theory to determine their stability. We thus identify distinct superradiant and lasing states in which the polariton modes are macroscopically populated. We map out the phase diagram of these states as a function of pump frequencies and strengths. Using parameters for transition metal dichalcogenides, we show that realisation of these phases may be practicably obtainable. The ability to manipulate phonon mode frequencies and attain steady-state populations of selected phonon modes provides a new tool for engineering correlated states of electrons.

Alexander Senichev, Zachariah O. Martin, Yongqiang Wang et al.

The integration of solid-state single-photon sources with foundry-compatible photonic platforms is crucial for practical and scalable quantum photonic applications. This study explores aluminum nitride (AlN) as a material with properties highly suitable for integrated on-chip photonics and the ability to host defect-center related single-photon emitters. We have conducted a comprehensive analysis of the creation of single-photon emitters in AlN, utilizing heavy ion irradiation and thermal annealing techniques. Subsequently, we have performed a detailed analysis of their photophysical properties. Guided by theoretical predictions, we assessed the potential of Zirconium (Zr) ions to create optically addressable spin defects and employed Krypton (Kr) ions as an alternative to target lattice defects without inducing chemical doping effects. With a 532 nm excitation wavelength, we found that single-photon emitters induced by ion irradiation were primarily associated with vacancy-type defects in the AlN lattice for both Zr and Kr ions. The density of these emitters increased with ion fluence, and there was an optimal value that resulted in a high density of emitters with low AlN background fluorescence. Under a shorter excitation wavelength of 405 nm, Zr-irradiated AlN exhibited isolated point-like emitters with fluorescence in the spectral range theoretically predicted for spin-defects. However, similar defects emitting in the same spectral range were also observed in AlN irradiated with Kr ions as well as in as-grown AlN with intrinsic defects. This result is supportive of the earlier theoretical predictions, but at the same time highlights the difficulties in identifying the sought-after quantum emitters with interesting properties related to the incorporation of Zr ions into the AlN lattice by fluorescence alone. The results of this study largely contribute to the field of creating quantum emitters in AlN by ion irradiation and direct future studies emphasizing the need for spatially localized Zr implantation and testing for specific spin properties.

F Bussolotti, T D Maddumapatabandi, K E J Goh

In this review, we present a perspective on the use of angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES (SARPES) for the study of the electronic properties of semiconducting transition metal dichalcogenides (TMDCs), a prime example of two-dimensional (2D) materials for valleytronics applications. In the introductory part, we briefly describe the structural and electronic properties of semiconducting TMDCs and the main valleytronics related physical effects. After a short presentation of theoretical methods utilized in the band structure and spin texture calculation of semiconducting TMDCs, we illustrate the basic principles and methodology of photoemission techniques and then provide a detailed survey on the electronic band structure studies of these materials. In particular, by selecting and comparing seminal results in the field, we highlight the critical role played by the sample preparation strategy on the amount and quality of information that can be extracted in the ARPES investigations of TMDCs. This is followed by a detailed discussion on the impact of interface potential landscape and doping on their electronic properties, considering the importance of their contact with metal electrode and/or dielectric substrate in determining the electrical transport in real devices’ architecture. Finally, we summarize key SARPES findings on the spin texture of TMDCs and conclude by pointing out current open issues and potential directions for future photoemission-based studies on these 2D systems.

K. A. Shaulskyi, S. P. Maydanyuk

Quantum effects in pycnonuclear reactions in compact stars at zero temperatures are studied with high precision. The reaction 16O + 16O was analyzed using the method of multiple internal reflections. The study of such reactions requires full consideration of quantum fluxes in the internal nuclear region. This reduces the rate and number of pycnonuclear reactions up to 1.8 times. This leads to the appearance of new states (which we call quasibound states) where the compound nuclear system is formed with maximal probability. As shown, the minimal energy of such a state is slightly higher than the energy of zero-mode oscillations in the lattice nodes in the pycnonuclear reaction, however, the probability of the formation of a compound system in a quasibound state is significantly greater than the corresponding probability in a state of zero-mode oscillations. It is reasonable to say that the frequency of reactions in quasi-bound states is more likely than in states of zero-mode oscillations. This can lead to significant changes in estimates of reaction rates in stars.

Andrea Marchesin, Bartolomeo Montrucchio, Mariagrazia Graziano et al.

The growth of cities and the resulting increase in vehicular traffic pose significant challenges to the environment and citizens' quality of life. To address these challenges, a new algorithm has been proposed that leverages the quantum annealing paradigm and D-wave's machines to optimize the control of traffic lights in cities. The algorithm considers traffic information collected from a wide urban road network to define activation patterns that holistically reduce congestion. An in-depth analysis of the model's behavior has been conducted by varying its main parameters. Robustness tests have been performed on different traffic scenarios, and a thorough discussion on how to configure D-wave's quantum annealers for optimal performance is presented. Comparative tests show that the proposed model outperforms traditional control techniques in several traffic conditions, effectively containing critical congestion situations, reducing their presence, and preventing their formation. The results obtained put in evidence the state of the art of these quantum machines, their actual capabilities in addressing the problem, and opportunities for future applications.

O. J. Clark, F. Freyse, L. V. Yashina et al.

Abstract The Dirac point of a topological surface state (TSS) is protected against gapping by time-reversal symmetry. Conventional wisdom stipulates, therefore, that only through magnetisation may a TSS become gapped. However, non-magnetic gaps have now been demonstrated in Bi2Se3 systems doped with Mn or In, explained by hybridisation of the Dirac cone with induced impurity resonances. Recent photoemission experiments suggest that an analogous mechanism applies even when Bi2Se3 is surface dosed with Au. Here, we perform a systematic spin- and angle-resolved photoemission study of Au-dosed Bi2Se3. Although there are experimental conditions wherein the TSS appears gapped due to unfavourable photoemission matrix elements, our photon-energy-dependent spectra unambiguously demonstrate the robustness of the Dirac cone against high Au coverage. We further show how the spin textures of the TSS and its accompanying surface resonances remain qualitatively unchanged following Au deposition, and discuss the mechanism underlying the suppression of the spectral weight.

V. I. Kovalchuk

In the framework of eiconal approximation and the double folding model, a formalism for calculating inclusive spectra of particles from stripping and fragmentation reactions involving light cluster nuclei is proposed. The cross-section of the 12C(3He, d)13N reaction at an incident particle energy of 81.4 MeV and the proton spectra from the deuteron fragmentation reaction with 56 MeV energies by 12C and 27Al nuclei are described. The calculated values satisfactorily fit the corresponding experimental data.

Hyungjin Kim, Gilad Perez

Axion-gluon interaction induces quadratic couplings between the axion and the matter fields. We find that, if the axion is an ultralight dark matter field, it induces small oscillations of the mass of the hadrons as well as other nuclear quantities. As a result, atomic energy levels oscillate. We use currently available atomic spectroscopy data to constrain such axion-gluon coupling. We also project the sensitivities of future experiments, such as ones using molecular and nuclear clock transitions. We show that current and near-future experiments constrain a finely-tuned parameter space of axion models. These can compete with or dominate the already-existing constraints from oscillating neutron electric dipole moment and supernova bound, in addition to those expected from near future magnetometer-based experiments. We also briefly discuss the reach of accelerometers and interferometers.

C. A. J. O'Hare, D. Loomba, K. Altenmüller et al.

Recoil imaging entails the detection of spatially resolved ionization tracks generated by particle interactions. This is a highly sought-after capability in many classes of detector, with broad applications across particle and astroparticle physics. However, at low energies, where ionization signatures are small in size, recoil imaging only seems to be a practical goal for micro-pattern gas detectors. This white paper outlines the physics case for recoil imaging, and puts forward a decadal plan to advance towards the directional detection of low-energy recoils with sensitivity and resolution close to fundamental performance limits. The science case covered includes: the discovery of dark matter into the neutrino fog, directional detection of sub-MeV solar neutrinos, the precision study of coherent-elastic neutrino-nucleus scattering, the detection of solar axions, the measurement of the Migdal effect, X-ray polarimetry, and several other applied physics goals. We also outline the R&D programs necessary to test concepts that are crucial to advance detector performance towards their fundamental limit: single primary electron sensitivity with full 3D spatial resolution at the $\sim$100 micron-scale. These advancements include: the use of negative ion drift, electron counting with high-definition electronic readout, time projection chambers with optical readout, and the possibility for nuclear recoil tracking in high-density gases such as argon. We also discuss the readout and electronics systems needed to scale-up such detectors to the ton-scale and beyond.

Jennifer Hasler, Neil Dick, Kushal Das et al.

Voltage biases are often required to bias Qubits, and yet applying a static bias requires separate chip wires, dramatically increasing the system complexity. An ideal approach would be having a nonvolatile digital or analog memory to avoid these issues. This article shows floating-gate (FG) structures could be used to set and forget potentials and tunnel barrier tuning as well as enable memory applications. It reports FG measurements at cryogenic temperatures (T = 4 K), enabling reprogrammable FG devices in cryogenic environments. Using a multipurpose FG test structure, measurements show the FG device and circuit operation as well as charge programming measurements based on electron tunneling and hot-electron injection at T = 4 K and T = 300 K. These results open applications in classical cryogenic computing, controlling quantum computation, and other cryogenic temperature applications.

Arnaud Mazier, Alexandre Bilger, Antonio E. Forte et al.

In this paper, we develop a framework for solving inverse deformation problems using the FEniCS Project finite element software. We validate our approach with experimental imaging data acquired from a soft silicone beam under gravity. In contrast with inverse iterative algorithms that require multiple solutions of a standard elasticity problem, the proposed method can compute the undeformed configuration by solving only one modified elasticity problem. This modified problem has a complexity comparable to the standard one. The framework is implemented within an open-source pipeline enabling the direct and inverse deformation simulation directly from imaging data. We use the high-level Unified Form Language (UFL) of the FEniCS Project to express the finite element model in variational form and to automatically derive the consistent Jacobian. Consequently, the design of the pipeline is flexible: for example, it allows the modification of the constitutive models by changing a single line of code. We include a complete working example showing the inverse deformation of a beam deformed by gravity as supplementary material.

Koen Bertels, A. Sarkar, T. Hubregtsen et al.

This article presents the definition and implementation of a quantum computer architecture to enable creating a new computational device—a quantum computer as an accelerator. A key question addressed is what such a quantum computer is and how it relates to the classical processor that controls the entire execution process. In this article, we present explicitly the idea of a quantum accelerator that contains the full stack of the layers of an accelerator. Such a stack starts at the highest level describing the target application of the accelerator. The next layer abstracts the quantum logic outlining the algorithm that is to be executed on the quantum accelerator. In our case, the logic is expressed in the universal quantum-classical hybrid computation language developed in the group, called OpenQL, which visualized the quantum processor as a computational accelerator. The OpenQL compiler translates the program to a common assembly language, called cQASM, which can be executed on a quantum simulator. The cQASM represents the instruction set that can be executed by the microarchitecture implemented in the quantum accelerator. In a subsequent step, the compiler can convert the cQASM to generate the eQASM, which is executable on a particular experimental device incorporating the platform-specific parameters. This way, we are able to distinguish clearly the experimental research toward better qubits, and the industrial and societal applications that need to be developed and executed on a quantum device. The first case offers experimental physicists with a full-stack experimental platform using realistic qubits with decoherence and error-rates, whereas the second case offers perfect qubits to the quantum application developer, where there is neither decoherence nor error-rates. We conclude the article by explicitly presenting three examples of full-stack quantum accelerators, for an experimental superconducting processor, for quantum accelerated genome sequencing and for near-term generic optimization problems based on quantum heuristic approaches. The two later full-stack models are currently being actively researched in our group.

Institute for Nuclear Research

Brief biography and scientific achievements of Leonid Anatoliyovych Bulavin in relation with his 75-th anniversary.

L. I. Chyrko, V. M. Revka, Yu. V. Chaikovskyi et al.

The comparison of experimental values of the critical brittle temperature ΔTF and reference temperature ΔT0 of VVER-1000 reactor vessel weld metal with an elevated content of manganese and nickel is performed. ΔTF and ΔT0 values are defined proceeding from the standard impact bend Charpy and Charpy cracked fracture toughness specimen tests, respectively. Specimens were irradiated in industrial reactors in the frame of surveillance specimen program up to the fast (E ≥ 0.5 MeV) neutron fluences corresponding to the NPP long term operation period. The research results showed the shifts ΔTF and ΔT0 to agree with each other. Besides, it was discovered that in the range of over-design fluences the design embrittlement model has a tendency to underestimate the critical brittle temperature shift.

Gerard Higgins, Chi Zhang, Fabian Pokorny et al.

The response of matter to fields underlies the physical sciences, from particle physics to astrophysics, and from chemistry to biophysics. We observe an atom's response to an electric quadrupole field to second- and higher orders; this arises from the atom's electric quadrupole polarizability and hyperpolarizabilities. We probe a single atomic ion which is excited to Rydberg states and confined in the electric fields of a Paul trap. The quadrupolar trapping fields cause atomic energy level shifts and give rise to spectral sidebands. The observed effects are described well by theory calculations.

Michael Pretko, Xie Chen, Yizhi You

Fractons are a new type of quasiparticle which are immobile in isolation, but can often move by forming bound states. Fractons are found in a variety of physical settings, such as spin liquids and elasticity theory, and exhibit unusual phenomenology, such as gravitational physics and localization. The past several years have seen a surge of interest in these exotic particles, which have come to the forefront of modern condensed matter theory. In this review, we provide a broad treatment of fractons, ranging from pedagogical introductory material to discussions of recent advances in the field. We begin by demonstrating how the fracton phenomenon naturally arises as a consequence of higher moment conservation laws, often accompanied by the emergence of tensor gauge theories. We then provide a survey of fracton phases in spin models, along with the various tools used to characterize them, such as the foliation framework. We discuss in detail the manifestation of fracton physics in elasticity theory, as well as the connections of fractons with localization and gravitation. Finally, we provide an overview of some recently proposed platforms for fracton physics, such as Majorana islands and hole-doped antiferromagnets. We conclude with some open questions and an outlook on the field.