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

Shivendra Singh Parihar, Florian Klemme, Shamiul Alam et al.

Ferroelectric superconducting quantum interference device (Fe-SQUID) has recently emerged as a viable option to realize superconducting computing due to its voltage-controlled switching, which is essential to build large-scale digital circuits. This is the first work to model Fe-SQUID-based logic circuits and develop standard cell libraries compatible with existing electronic design automation (EDA) tool flows. We provide a comprehensive evaluation of the power consumption and performance of a wide range of Fe-SQUID-based arithmetic circuits, benchmarking them against the state-of-the-art 5 nm fin field-effect transistor (FinFET)-based circuits. Our 5 nm FinFET transistor model is validated against industrial measurements. The validation is conducted not only at room temperature but also at extremely low temperatures, down to 10 K, for fair comparisons against Fe-SQUID superconducting circuits. Our findings revealed that contrary to CMOS-based circuits, circuits realized using Fe-SQUID dissipate significantly more power. This presents a substantial challenge within the constraints of limited cooling power budgets in state-of-the-art cryostats.

Xinyi Jiang, Qingzheng Qiu, Cheng Peng et al.

Abstract Spin-orbit entangled materials have attracted widespread interest due to the novel magnetic phenomena arising from the interplay between spin-orbit coupling and electronic correlations. However, the intricate nature of spin interactions within Kiteav materials complicates the precise measurement of low-energy spin excitations. Using Na2Co2TeO6 as an example, we study these low-energy spin excitations using the time-resolved resonant elastic x-ray scattering (tr-REXS). Our observations unveil remarkably slow spin dynamics at the magnetic peak, whose recovery timescale is several nanoseconds. This timescale aligns with the extrapolated spin gap of ~1 μeV, obtained by density matrix renormalization group (DMRG) simulations in the thermodynamic limit. The consistency demonstrates the efficacy of tr-REXS in discerning low-energy spin gaps inaccessible to conventional spectroscopic techniques.

O. V. Zhukovskyi, V. P. Krasnov, I. G. Patseva et al.

This study investigates the current distribution of 137Cs in the tissues and organs of black alder (Alnus glutinosa (L.) Gaertn.) growing under different forest site conditions in the Polissia region of Ukraine. The most intensive uptake of the radionuclide into various parts of the trunk and crown was observed in wet, relatively fertile forest sites. The aggregated transfer factor of 137Cs increased from moist to wet, relatively fertile conditions, with values changing as follows: from 0.5 to 5.2 m2·kg-1·10-3 in leaves, from 1.7 to 8.3 m2·kg-1·10-3 in one-year-old shoots, from 1.0 to 4.9 m2·kg-1·10-3 in two-year-old shoots, from 0.7 to 3.9 m2·kg-1·10-3 in fine branches, from 0.5 to 2.9 m2·kg-1·10-3 in coarse branches, from 2.1 to 10.2 m2·kg-1·10-3 in fruits, and from 2.5 to 14.1 m2·kg-1·10-3 in male inflorescences. Statistically significant differences in aggregated transfer factors were observed among nearly all crown components across moist, damp, and wet site conditions. Additionally, a slight increase in the 137Cs content was recorded from the base to the top of the crown in wet, relatively fertile sites.

V. I. Kovalchuk

Within the framework of eikonal approximation and the double folding model, a formalism for calculating the angular dependencies of nucleon polarizations arising in two-nucleon transfer reactions is proposed. The polarizations of protons from (3He, p) reactions on 7Li, 9Be, and 12C targets with residual nuclei in the ground state at an incident particle energy of 33 MeV are described. The calculated polarization values satisfactorily fit the corresponding experimental data.

Chou-Wei Kiang, Jean-Fu Kiang

Nitrogen-vacancy (NV) ensembles are viable magnetometers to be implemented on nanosatellites for monitoring geomagnetic fluctuations, which are credible precursors for predicting earthquakes at short notice. In this work, a Haar wavelet-based quantum sensing method is proposed to reconstruct the time-varying waveform of geomagnetic fluctuations in the very low frequency band. To collect different frequency components of fluctuations waveform at once, we propose a schematic to employ multiple NV ensembles (NVEs), with each controlled by an independent microwave source. Berry sequences are applied on one set of NVEs to extract the scaling coefficients from accumulated geometric phases to reconstruct near-dc components of a waveform. Spin-echo sequences are applied to another set of NVEs to extract the Haar wavelet coefficients from the dynamic phases to reconstruct high-frequency components. The efficacy of the proposed sensing protocol implemented on multiple NVEs is validated by reconstructing a waveform of geomagnetic fluctuations from a DEMETER satellite dataset through simulations. Each NVE is assumed to contain <inline-formula><tex-math notation="LaTeX">$N = 10^{8}$</tex-math></inline-formula> uncorrelated NV centers. The application of a Berry sequence to each NVE can achieve the maximum detectable magnetic field of over <inline-formula><tex-math notation="LaTeX">$460 \ \mu$</tex-math></inline-formula>T, resolving the issues of phase ambiguity and hyperfine-induced detuning if conventional Ramsey sequence were applied. The feasibility of the proposed simulation scenario considering spin-bath noise within an NVE is justified by simulations. The effects of wavelet scales, Rabi frequency in Berry sequence, and number of NV centers in each NVE are analyzed. The proposed NVE quantum sensors operated with the proposed sensing protocol can be installed on nanosatellites to monitor global geomagnetic fluctuations, with sub-<inline-formula><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula>s temporal resolution in the near future.

A.A. Burkov

Artur Erbe

Kazi Ranjibul Islam, Andrey Chubukov

Abstract We analyze superconductivity in a multi-orbital fermionic system near the onset of a nematic order, using doped FeSe as an example. We associate nematicity with spontaneous polarization between d xz and d yz orbitals. We derive pairing interaction, mediated by soft nematic fluctuations, and show that it is attractive, and its strength depends on the position on the Fermi surface. As the consequence, right at the nematic quantum-critical point (QCP), superconducting gap opens up at T c only at special points and extends into finite arcs at T < T c. In between the arcs the Fermi surface remains intact. This leads to highly unconventional behavior of the specific heat, with no jump at T c and seemingly finite offset at T = 0. We discuss gap structure and pairing symmetry away from a QCP and compare nematic and spin-fluctuation scenarios. We apply the results to FeSe1−x S x and FeSe1−x Te x .

Takla Nateeboon, Chanaprom Cholsuk, Tobias Vogl et al.

Anastasiia Ciers, Alexander Jung, Joachim Ciers et al.

Nanomechanical resonators with high quality factors ( Q _m ) enable mechanics-based quantum technologies, in particular quantum sensing and quantum transduction. High- Q _m nanomechanical resonators in the kHz to MHz frequency range can be realized in tensile-strained thin films that allow the use of dissipation dilution techniques to drastically increase Q _m . In our work, we study the material properties of tensile-strained piezoelectric films made from aluminium nitride (AlN). We characterize crystalline AlN films with a thickness ranging from 45 nm to 295 nm, which are directly grown on Si(111) by metal–organic vapour-phase epitaxy. We report on the crystal quality and surface roughness, the piezoelectric response, and the residual and released stress of the AlN thin films. Importantly, we determine the intrinsic quality factor of the films at room temperature in high vacuum. We fabricate and characterize AlN nanomechanical resonators that exploit dissipation dilution to enhance the intrinsic quality factor by utilizing the tensile strain in the film. We find that AlN nanomechanical resonators below 200 nm thickness exhibit the highest $Q_\text{m}\times f_\text{m}$ -product, on the order of 10 ^12  Hz. We discuss possible strategies to optimize the material growth that should lead to devices that reach even higher $Q_\text{m}\times f_\text{m}$ -products. This will pave the way for future advancements of optoelectromechanical quantum devices made from tensile-strained piezoelectric AlN.

Hongtao Rong, Zhenqiao Huang, Xin Zhang et al.

Abstract Space groups describing the symmetry of lattice structure allow the emergence of fermionic quasiparticles with various degeneracy in the band structure. Theoretical efforts have predicted many materials hosting fermions with the highest degeneracy, i.e., eightfold fermions, yet lacking experimental realization. Here, we explore the band degeneracies in TaCo2Te2 crystals. Through systematic experimental and theoretical analyses, we establish TaCo2Te2 as a nonsymmorphic crystal with negligible spin–orbit coupling (SOC) and long-range magnetic order. These critical properties guarantee the realization of practical eightfold fermions and fourfold van Hove singularity, as directly observed by photoemission spectroscopy. TaCo2Te2 serves as a topological quantum critical platform, which can be tuned into various magnetic, topologically trivial, and nontrivial phases by adding strain, magnetic field, or SOC. The latter is demonstrated by our first-principles calculations, which show that enhancing SOC in TaCo2Te2 will promote the experimental observation of bulk hourglass fermions. Our results establish TaCo2Te2 as a platform to explore the interplay between symmetry and band topology.

Peizhi Mai, Edwin W. Huang, Jiachen Yu et al.

Abstract Motivated by recent experimental work on moiré systems in a strong magnetic field, we compute the compressibility as well as the spin correlations and Hofstadter spectrum of spinful electrons on a honeycomb lattice with Hubbard interactions using the determinantal quantum Monte Carlo method. While the interactions in general preserve quantum and anomalous Hall states, emergent features arise corresponding to an antiferromagnetic insulator at half-filling and other incompressible states following the Chern sequence ± (2N + 1). These odd integer Chern states exhibit strong ferromagnetic correlations and arise spontaneously without any external mechanism for breaking the spin-rotation symmetry. Analogs of these magnetic states should be observable in general interacting quantum Hall systems. In addition, the interacting Hofstadter spectrum is qualitatively similar to the experimental data at intermediate values of the on-site interaction.

Yong Hu, Xianxin Wu, Andreas P. Schnyder et al.

Abstract The recently discovered layered kagome superconductors AV3Sb5 (A = K, Rb, Cs) have garnered significant attention, as they exhibit an intriguing combination of superconductivity, charge density wave (CDW) order, and nontrivial band topology. As such, these kagome systems serve as an exceptional quantum platform for investigating the intricate interplay between electron correlation effects, geometric frustration, and topological electronic structure. A comprehensive understanding of the underlying electronic structure is crucial for unveiling the nature and origin of the CDW order, as well as determining the electron pairing symmetry in the kagome superconductors. In this review, we present a concise survey of the electronic properties of AV3Sb5, with a particular focus on the insights derived from angle-resolved photoemission spectroscopy (ARPES). Through the lens of ARPES, we shed light on the electronic characteristics of the kagome superconductors AV3Sb5, which will pave the way for exciting new research frontiers in kagome-related physics.

Saikat Banerjee, Wei Zhu, Shi-Zeng Lin

Abstract Quantum spin liquids (QSL) have emerged as a captivating subject within interacting spin systems that exhibit no magnetic ordering even at the lowest temperature accessible experimentally. However, definitive experimental evidence remains elusive. In light of the recent surge in theoretical and experimental interest in the half-filled Hubbard model on a triangular lattice, which offers the potential for stabilizing a chiral QSL, we investigate the electromagnetic signatures of this phase to facilitate experimental detection. Utilizing a combination of parton mean-field theory and unbiased density-matrix renormalization group calculations, we systematically examine the electrical charge and orbital electrical current associated with a spinon excitation in the chiral QSL. Additionally, we calculate the longitudinal and transverse optical conductivities below the Mott gap. Furthermore, employing quantum field theory analysis, we unravel the connection between spinon excitations and emergent as well as physical gauge fields. Our results demonstrate that the chiral QSL phase exhibits a distinct electromagnetic response, even within a Mott insulator regime. This finding holds great potential for enabling the experimental detection of this long-sought-after phase.

Zhao-Cai Wang, Lei Chen, Shuang-Shuang Li et al.

Abstract Linear magnetoresistance (LMR) is a special case of a magnetic-field induced resistivity response, which has been reported in highly disordered semiconductor systems and in topological materials. In this work, we observe LMR effect in half-metallic perovskite Sr2CrMoO6 thin films, of which the maximum MR value exceeds +1600% at 2 K and 14 T. It is an unusual behavior in ferrimagnetic double perovskite material like Sr2CrMoO6, which are known for intrinsic tunneling-type negative magnetoresistance. In the thin films, the high carriers’ density (~1022 cm−3) and ultrahigh mobility (~104 cm2 V−1 s−1) provide a low-resistivity (~10 nΩ·cm) platform for spin-polarized current. Our DFT calculations and magnetic measurements further support the half-metal band structure. The LMR effect in Sr2CrMoO6 could possibly originate from transport behavior that is governed by the guiding center motion of cyclotron orbitals, where the magnetic domain structure possibly provides disordered potential. The ultrahigh mobility and LMR in this system could broaden the applications of perovskites, and introduce more research on metallic oxide ferri-/ferro-magnetic materials.

Hasan Bircan

A. P. Voiter, M. I. Doronin, O. M. Kovalev et al.

Data acquisition system with a flexible architecture for studying multiparameter nuclear reactions, based on the extensive use of the devices with programmable logic, is considered. The technical means of the system and its software are described.

Tetsuji Saito

An attempt was made to produce Sm-Fe-N/Co-B composite magnets by chemical reduction. It was found that a composite powder consisting of Sm-Fe-N particles coated with fine Co-B particles could be obtained by chemical reduction. The Sm-Fe-N/Co-B composite powder acted as a single hard magnetic phase and showed a smooth hysteresis loop. The composite powder exhibited a higher remanence of 93.1 Am2/kg and a higher coercivity of 0.45 MA/m than a mixture of the Sm-Fe-N powder and Co-B powder prepared by a similar procedure but using a higher concentration of aqueous solution for the chemical reduction.

V. T. Kupryashkin, B. V. Ostapenko

Conversion spectrum of the K- and L-lines of E0-transitions was studied with high-resolution magnetic spectrometer π√2. The intensity of the E0-transitions (in relation to the most intense transition of 328 keV) is: 1479 keV, Ik = 2.00(5); 1547 keV, Ik = 6.1(5)⋅10-2; 2085 keV, Ik = 1.10(5)⋅10-1. For the first time, measurements of the L-peaks of the E0-transition in the region of more than 1 MeV have been made and the relation L1 / L2 = 26(7) for 1479 keV has been established. Based on the measurements, the values of parameters q2 and X were calculated for: 1479 keV - q2 = 11.5(9), X = 0.44(6); 1547 keV - q2 = 0.47(6), X = 0.020(4); 2085 keV - q2 = 61(2), X = 5.6(3). Comparison was made with existing nuclear models.

Chih-Wei Luo, Po Chung Cheng, Shun-Hung Wang et al.

Iron-based superconductors: Hidden nematic and magnetic fluctuations in iron selenide Ultrafast spectroscopy unveils hidden nematic fluctuations and a spin subsystem in the iron-based superconductor iron selenide. Layered iron-based materials recently emerged as a new class of high temperature superconductor. The mechanism of superconductivity in these materials, however, is a contentious issue. Nematic ordering is thought to be a key ingredient, but the apparent absence of magnetic ordering in iron selenide, which is the iron-based superconductor with the simplest structure, has caused confusion over what drives the nematicity. An international team of researchers led by Chih-Wei Luo and Jenh-Yih Juang from National Chiao Tung University use polarized ultrafast spectroscopy to unveil a hidden spin subsystem in FeSe, along with both nematic and magnetic fluctuations at relatively high temperatures, providing insights into the driving factors of nematicity in this fascinating material.