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DOE OSTI2021

Width-bending characteristic of REBCO HTS tape and flat-tape Rutherford-type cabling

Abstract The width-bending behaviors for a rare earth barium copper oxide (REBCO) high-temperature superconducting (HTS) tape have been investigated. It has been found experimentally that the width-bending strain of a Yttrium Barium Copper Oxide (YBCO) tape does not degrade the critical current as much as is expected from the axial strain. The critical current is not directly affected by the width-bending strain but by the axial strain, which the width-bending strain generates by the Poisson effect. Since Poisson’s ratio is about 0.3, the axial strain effective on the critical current is about 30% of the width-bending strain. Therefore, the width-bending strain of even 1.5% degrades the critical current by only 15% if the REBCO layer side is bent inward. However, the critical current degraded by more than 70% when the REBCO layer is outward. The width-bending effects on the critical current have been further examined, considering Poisson’s ratio changes and the neutral plane shift of the REBCO tape substrate. Those changes would occur when the material yields due to severe width-bending. Based on the width-bending of REBCO tapes, flat-tape Rutherford-type cabling is discussed. A REBCO Rutherford-type cable can provide various advantages, especially for narrow-tape cabling. The flat-tape Rutherford-type cable has better characteristics against an electromagnetic transverse Lorentz force. Furthermore, the tape length of the cable can be approximately the same as the cable length allowing for excellent tape usage. REBCO Rutherford-type cabling will be a promising high-current, high-field cabling method using thin substrate REBCO tapes. It will be useful for AC ramp-field and pulse-field applications with low AC losses and low shield currents. It notes that the filaments in the cable are symmetrically distributed in parallel. Therefore, each filament’s inductance is uniform, and a uniform current distribution among the filaments can be obtained.

Physics↗

DOE OSTI2023

First test results of the trans-impedance amplifier stage of the ultra-fast HPSoC ASIC

Abstract We present the first results from the HPSoC ASIC designed for readout of Ultra-fast Silicon Detectors. The 4-channel ASIC manufactured in 65 nm CMOS by TSMC has been optimized for 50 μm thick AC-LGAD. The evaluation of the analog front end with β-particles impinging on 3 × 3 AC-LGAD arrays (500 μm pitch, 200 × 200 μm 2 metal) confirms a fast output rise time of 600 ps and good timing performance with a jitter of 45 ps. Further calibration experiments and TCT laser studies indicate some gain limitations that are being investigated and are driving the design of the second-generation pre-amplification stages to reach a jitter of 15 ps.

Instruments & Instrumentation↗

DOE OSTI2025

Ratchet effects in cyclic pattern formation systems with competing interactions

Ratchet effects can appear for particles interacting with an asymmetric potential under ac driving or for a thermal system in which a substrate is periodically flashed. Here, we show that a different type of collective ratchet effect can arise for a pattern-forming system coupled to an asymmetric substrate when the interaction potential between the particles is periodically oscillated in order to cycle the system through different patterns. We consider particles with competing short-range attraction and long-range repulsion subjected to time-dependent oscillations of the ratio between the attractive and repulsive interaction terms, which causes the system to cycle periodically between crystal and bubble states. In the presence of the substrate, this system exhibits both a positive and a reversed ratchet effect, and we show that there is a maximum in the ratchet efficiency as a function of interaction strength, ac drive frequency, and particle density. In conclusion, our results could be realized for a variety of pattern-forming systems on asymmetric substrates where the pattern type or particle interactions can be oscillated.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Metrology of Time-Domain Soft X-Ray Attosecond Pulses and Reevaluation of Pulse Durations of Three Recent Experiments

Attosecond pulses in the soft x-ray (SXR) to water-window energy region offer the tools for creating and studying target-specific localized inner-shell electrons or holes in materials, enabling monitoring or controlling charge and energy flows in a dynamic system on attosecond timescales. Recently, a number of laboratories have reported generation of continuum harmonics in the hundred-electron-volt to kilovolt region with few-cycle long-wavelength mid-infrared lasers. These harmonics have the bandwidth to support pulses with durations of a few to a few-ten attoseconds. But harmonics generated in a gas medium have attochirps that cannot be fully compensated by materials over a broad spectral range; thus, realistically what are the typical shortest attosecond pulses that one can generate? To answer this question, it is essential that the temporal attosecond pulses be accurately characterized. By reanalyzing the soft x-ray attosecond metrology reported in three recent experiments using a newly developed broadband phase retrieval algorithm, we demonstrate here that the generated attosecond pulses in the first two papers have durations of about 60 as, longer than what they have reported. Similarly, the duration from the third experiment is retrieved to be about half of the 322-as upper limit cited in that work. We also introduce the autocorrelation (AC) of the streaking spectrogram. By comparing the ACs from the experiments and from the retrieved SXR pulses, the accuracy of the retrieved results can be directly visualized. Our retrieval method is fast and accurate, and it shall provide a powerful tool for the metrology of the emerging few-ten-attosecond pulses.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2020

Nonlinear dynamics and dissipation of a curvilinear vortex driven by a strong time-dependent Meissner current

Here, we report numerical simulations of large-amplitude oscillations of a trapped vortex line under a strong ac magnetic field $\textit{H(t) = H}$ sin$\textit{ωt}$ parallel to the surface. The power dissipated by an oscillating vortex segment driven by the surface ac Meissner currents was calculated by taking into account the nonlinear vortex line tension, vortex mass, and a nonlinear Larkin-Ovchinnikov (LO) viscous drag coefficient $\textit{η(v)}$. We show that the LO decrease of $\textit{η(v)}$ with the vortex velocity $\textit{v}$ can radically change the field dependence of the surface resistance R i ( H ) caused by trapped vortices. At low frequencies, $R_i(H)$ exhibits a conventional increase with $\textit{H}$, but as $\textit{ω}$ increases, the surface resistance becomes a nonmonotonic function of $\textit{H}$ which decreases with $\textit{H}$ at higher fields. The effects of frequency, pin spacing, and the mean-free path $l_i$ on the field dependence of $R_i(H)$ were calculated. It is shown that, as the surface gets dirtier and $l_i$ decreases, the anomalous drop of $R_i(H)$ with $\textit{H}$ shifts to lower fields which can be much smaller than the lower critical magnetic field. Our numerical simulations also show that the LO decrease of $\textit{η(v)}$ with $\textit{v}$ can cause a vortex bending instability at high field amplitudes and frequencies, giving rise to the formation of dynamic kinks along the vortex. Measurements of $R_i(H)$ caused by sparse vortices trapped perpendicular to the surface can offer opportunities to investigate an extreme nonlinear dynamics of vortices driven by strong current densities up to the depairing limit at low temperatures. The behavior of $R_i(H)$, which can be tuned by varying the rf frequency or concentration of nonmagnetic impurities, is not masked by strong heating effects characteristic of dc or pulse transport measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Photoinduced anomalous Hall effect in two-dimensional transition metal dichalcogenides

A circularly polarized ac pump field illuminated near resonance on two-dimensional transition metal dichalcogenides (TMDs) produces an anomalous Hall effect in response to a dc bias field. In this work, we develop a theory for this photoinduced anomalous Hall effect in undoped TMDs irradiated by a strong coherent laser field. The strong field renormalizes the equilibrium bands and opens up a dynamical energy gap where single-photon resonance occurs. The resulting photon dressed states, or Floquet states, are treated within the rotating-wave approximation. A quantum kinetic equation approach is developed to study the nonequilibrium density matrix and time-averaged transport currents under the simultaneous influence of the strong ac pump field and the weak dc probe field. Dissipative effects are taken into account in the kinetic equation that captures relaxation and dephasing. The photoinduced longitudinal and Hall conductivities display notable resonant signatures when the pump field frequency reaches the spin-split interband transition energies. Rather than valley polarization, we find that the anomalous Hall current is mainly driven by the intraband response of photon-dressed electron populations near the dynamical gap at both valleys, accompanied by a smaller contribution due to the interband response. In conclusion, these findings highlight the importance of photon-dressed bands and nonequilibrium distribution functions in achieving a proper understanding of the photoinduced anomalous Hall effect in a strong pump field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2021

Phenomenological model of the third-harmonic magnetic response due to superconducting fluctuations: Application to Sr 2 RuO 4

Here, we employ the phenomenological Lawrence-Doniach model to compute the contributions of the superconducting fluctuations to the third-harmonic magnetic response, denoted here by $\bar{M_3}$, which can be measured in a precise way using ac magnetic fields and lock-in techniques. We show that, in an intermediate temperature regime, this quantity behaves as the third-order nonlinear susceptibility, which shows a power-law dependence with the reduced temperature ε = $\frac{T-T_c}{T_c}$ as ε -5/2 . Very close to T c , however, $\bar{M_3}$ saturates due to the nonzero amplitude of the ac field. We compare our theoretical results with experimental data for three conventional superconductors—lead, niobium, and vanadium—and for the unconventional superconductor Sr 2 RuO 4 (SRO). We find good agreement between theory and experiment for the elemental superconductors, although the theoretical values for the critical field systematically deviate from the experimental ones. In the case of SRO, however, the phenomenological model completely fails to describe the data, as the third-harmonic response remains sizable over a much wider reduced temperature range compared to Pb, Nb, and V. We show that an inhomogeneous distribution of T c across the sample can partially account for this discrepancy, since regions with a locally higher T c contribute to the fluctuation $\bar{M_3}$ significantly more than regions with the “nominal” T c of the clean system. However, the exponential temperature dependence of $\bar{M_3}$ first reported by Pelc et al. [Nat. Commun. 10, 2729 (2019)] is not captured by the model with inhomogeneity. We conclude that, while inhomogeneity is an important ingredient to understand the superconducting fluctuations of SRO and other perovskite superconductors, additional effects may be at play, such as non-Gaussian fluctuations or rare-region effects.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2022

Slow spin dynamics and quantum tunneling of magnetization in the dipolar antiferromagnet DyScO 3

Here, we present a comprehensive study of static and dynamic magnetic properties in the Ising-like dipolar antiferromagnet (AFM) DyScO 3 by means of DC and AC magnetization measurements supported by classical Monte Carlo calculations. Our AC-susceptibility data show that the magnetic dynamics exhibit a clear crossover from an Arrhenius-like regime to quantum tunneling of magnetization (QTM) at T*=10K. Below T N =3.2K, DyScO 3 orders in an antiferromagnetic GxAy-type magnetic structure and the magnetization dynamics slow down to the minute timescale. The low-temperature magnetization curves exhibit complex hysteretic behavior, which depends strongly on the magnetic field sweep rate. We demonstrate that the low-field anomalies on the magnetization curve are related to the metamagnetic transition, while the hysteresis at higher fields is induced by a strong magnetocaloric effect. Our theoretical calculations, which take into account dipolar interaction between Dy 3+ moments, reproduce essential features of the magnetic behavior of DyScO 3 . We demonstrate that DyScO 3 represents a rare example of an inorganic compound, which exhibits QTM at a single-ion level and magnetic order due to classical dipolar interaction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2022

Driven responses of periodically patterned superconducting films

Here, we simulate the motion of a commensurate vortex lattice in a periodic lattice of artificial circular pinning sites having different diameters, pinning strengths, and spacings using the time-dependent Ginzburg-Landau formalism. Above some critical DC current density J c , the vortices depin, and the resulting steady-state motion then induces an oscillatory electric field E (t) with a defect "hopping" frequency f 0 , which depends on the applied current density and the pinning landscape characteristics. The frequency generated can be locked to an applied AC current density over some range of frequencies, which depends on the amplitude of the DC as well as the AC current densities. Both synchronous and asynchronous collective hopping behaviors are studied as a function of the supercell size of the simulated system and the (asymptotic) synchronization threshold current densities determined.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2023

Interplay of structure and magnetism in LuFe 4 ⁢Ge 2 tuned by hydrostatic pressure

Lu⁢Fe 4 ⁢Ge 2 crystallizes in the Zr⁢Fe 4 ⁢Si 2 -type structure, hosting chains of Fe tetrahedra giving rise to geometric frustration and low dimensionality. The compound orders antiferromagnetically at around 36 K accompanied by a simultaneous structural transition from a tetragonal phase to an orthorhombic phase. The hydrostatic pressure dependence of the magnetic and structural transitions is investigated using electrical transport, AC magnetic susceptibility, AC calorimetry, M⁢össbauer, muon-spin relaxation (μ⁢SR), and x-ray-diffraction measurements. External pressure suppresses the first-order transition to the antiferromagnetic phase (AFM1) around 1.8 GPa. The structural transition is largely unaffected by pressure and remains between 30 to 35 K for pressures up to 2 GPa. A second antiferromagnetic phase (AFM2) is observed at higher pressures. The transition from the paramagnetic to the AFM2 phase is of second-order nature and appears to be connected to the structural transition. The magnetic volume fraction obtained from μ⁢SR and M⁢össbauer measurements reveal that the entire sample undergoes magnetic ordering in both magnetic phases. In addition, similar low-temperature muon-precession frequencies in AFM1 and AFM2 phases point at similar ordered moments and magnetic structures in both phases. Our results further indicate enhanced magnetic fluctuations in the pressure-induced AFM2 phase. The experimental observations together with density functional theory calculations suggest that the magnetic- and structural-order parameters in Lu⁢Fe 4 ⁢Ge 2 are linked by magnetic frustration, causing the simultaneous magnetostructural transition.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2023

Quantum Logic Enhanced Sensing in Solid-State Spin Ensembles

We demonstrate quantum logic enhanced sensitivity for a macroscopic ensemble of solid-state, hybrid two-qubit sensors. We achieve over a factor of 30 improvement in the single-shot signal-to-noise ratio, translating to an ac magnetic field sensitivity enhancement exceeding an order of magnitude for time-averaged measurements. Using the electronic spins of nitrogen vacancy (NV) centers in diamond as sensors, we leverage the on-site nitrogen nuclear spins of the NV centers as memory qubits, in combination with homogeneous and stable bias and control fields, ensuring that all of the ~10 9 two-qubit sensors are sufficiently identical to permit global control of the NV ensemble spin states. We find quantum logic sensitivity enhancement for multiple measurement protocols with varying optimal sensing intervals, including XY8 and DROID-60 dynamical decoupling, as well as correlation spectroscopy, using an applied ac magnetic field signal. The results are independent of the nature of the target signal and broadly applicable to measurements using NV centers and other solid-state spin ensembles. Furthermore, this work provides a benchmark for macroscopic ensembles of quantum sensors that employ quantum logic or quantum error correction algorithms for enhanced sensitivity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2020

Magnetic polarons and spin-glass behavior in insulating La 1-x Sr x CoO 3 (x = 0.125 and 0.15)

The evolution of magnetic polarons in Sr doped La Co O 3 ( La 1 - x Sr x Co O 3 ) single crystal and polycrystalline samples are investigated by employing dc and ac magnetic measurement and small angle neutron scattering (SANS) techniques. The effect of magnetic field and temperature on magnetic polarons is experimentally studied for La 0.875 Sr 0.125 Co O 3 and La 0.85 Sr 0.15 Co O 3 compounds that belong to the spin glass insulating regime of the broader compositional phase diagram of this system. Langevin analyses of the isothermal magnetization curves in the notional paramagnetic regime prove the existence of magnetic polarons with large moments. The dc field superimposed ac susceptibility data and the analysis of the glassy dynamics prove that the size of polarons in 15% Sr doped crystal increase as the field is increased while the field effect is not visible in the 12.5% Sr doped crystal. A polycrystalline sample of La 0.85 Sr 0.15 Co O 3 is analyzed by SANS experiments, which confirm nonzero correlation length at temperatures far above the macroscopic ordering temperature and hence the presence of magnetic polarons.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Strongly Interacting, Two-Dimensional, Dipolar Spin Ensembles in (111)-Oriented Diamond

Systems of spins with strong dipolar interactions and controlled dimensionality enable new explorations in quantum sensing and simulation. In this work, we investigate the creation of strong dipolar interactions in a two-dimensional ensemble of nitrogen-vacancy (NV) centers generated via plasma-enhanced chemical vapor deposition on (111)-oriented diamond substrates. We find that diamond growth on the (111) plane yields high incorporation of spins, both nitrogen and NV centers, where the density of the latter is tunable via the miscut of the diamond substrate. Our process allows us to form dense, preferentially aligned, 2D NV ensembles with volume-normalized ac sensitivity down to η ac = 810 pT μ m 3 / 2 Hz − 1 / 2 . Furthermore, we show that (111) affords maximally positive dipolar interactions among a 2D NV ensemble, which is crucial for leveraging dipolar-driven entanglement schemes and exploring new interacting spin physics. Published by the American Physical Society 2025

Hughes, Lillian B. (ORCID:0000000210201661)↗

DOE OSTI2025

Subharmonic Shapiro steps in depinning dynamics of a two-dimensional solid dusty plasma modulated by one-dimensional nonlinear deformed periodic substrates

Langevin dynamical simulations are performed to investigate the depinning dynamics of a two-dimensional (2D) solid dusty plasma, which is modulated by one-dimensional (1D) nonlinear deformed periodic substrates, and also driven by the combination of the DC and AC forces. As the DC driving force increases gradually, pronounced subharmonic and harmonic Shapiro steps are discovered under the combined modulation of the deformed substrate and the external AC drive. Here, these observed subharmonic and harmonic Shapiro steps are attributed to the dynamic mode locking. The data analysis results indicate that the nonlinear deformed substrate strongly influences these subharmonic Shapiro steps, which can be accurately diagnosed using the fraction of sixfold coordinated particles. Furthermore, the diagnostic of the kinetic temperature clearly indicates the difference between harmonic and subharmonic Shapiro steps, i.e., the particle motion is slightly less synchronized at subharmonic Shapiro steps, caused by the unstable locations of the deformed substrate.

36 MATERIALS SCIENCE↗

DOE OSTI2024

X-ray-induced piezoresponse during X-ray photon correlation spectroscopy of PbMg 1/3 Nb 2/3 O 3

X-ray photon correlation spectroscopy (XPCS) holds strong promise for observing atomic-scale dynamics in materials, both at equilibrium and during non-equilibrium transitions. Here an in situ XPCS study of the relaxor ferroelectric PbMg 1/3 Nb 2/3 O 3 (PMN) is reported. A weak applied AC electric field generates strong response in the speckle of the diffuse scattering from the polar nanodomains, which is captured using the two-time correlation function. Correlated motions of the Bragg peak are also observed, which indicate dynamic tilting of the illuminated volume. This tilting quantitatively accounts for the observed two-time speckle correlations. The magnitude of the tilting would not be expected solely from the modest applied field, since PMN is an electrostrictive material with no linear strain response to the field. A model is developed based on non-uniform static charging of the illuminated surface spot by the incident micrometre-scale X-ray beam and the electrostrictive material response to the combination of static and dynamic fields. The model qualitatively explains the direction and magnitude of the observed tilting, and predicts that X-ray-induced piezoresponse could be an important factor in correctly interpreting results from XPCS and nanodiffraction studies of other insulating materials under applied AC field or varying X-ray illumination.

36 MATERIALS SCIENCE↗

DOE OSTI2020

20-kW Bi-directional Wireless Power Transfer System with Energy Storage System Connectivity

Onar, Omer↗

DOE OSTI2021

A Novel Bi-directional AC/DC - DC/AC Wireless Power Transfer System for Grid Support Applications

The severity of the economic impact caused by grid outages has been the driving factor for creating innovative solutions that increases interest for the deployment of distributed energy resources to reduce the impact of grid outages. This paper presents a novel topology for providing export power applications. Proposed topology can be used for grid (primary)-side of bi-directional wireless power transfer (WPT) systems, mobile energy storage systems (ESSs), and electric vehicle (EV) batteries. The proposed concept here achieves energy transfer between sources by using a hybrid frequency bi-directional ac/dc converter without an additional front-end converter stage compared to the conventional systems. Due to inherent merit of the proposed bi-directional ac/dc converter, ac input with 60 Hz grid frequency can be directly transferred through the wireless coils and can be directly converted to the dc. Results demonstrate the performance and the functionality of the single-phase bi-directional system with the input / output of 110 V ac,rms and 200 V dc at 1 kW power. Full paper will demonstrate the converter operation at 10 kW power level with additional features and control aspects.

Asa, Erdem↗

DOE OSTI2023

Medium Voltage Solid State Transformer for Extreme Fast Charging Applications

A modular and scalable solid state transformer (SST) with direct medium voltage (MV) AC connectivity is proposed to enable DC extreme fast charging (XFC) of electric vehicles. Single-phase-modules (SPMs), each consisting of an active-front-end (AFE) stage and an isolated DC-DC stage, are connected in input-series-output-parallel (ISOP) configuration. The modular hardware is co-designed with decentralized control of the DC-DC stages where voltage and power balancing are achieved by each SPM using only its local sensor feedback; a centralized controller (CC) regulates the low voltage (LV) DC bus through the AFE stages without any sensor feedback form the SPMs. The controller architecture contrasts sharply with the prior art for MV AC to LV DC SSTs where high-speed bidirectional communication among SPMs and a CC are required for module-level voltage and power balancing, which severely limits the scalability and practical realization of higher voltage and higher power units. Detailed small-signal analysis and controller design guidelines are developed. Furthermore, a soft start-up strategy is presented. The proposed converter and control structure are validated through simulation and experimental results.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗