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Open access publications by faculty, postdocs, and graduate students in the Department of Physics and Astronomy.
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- ItemAmmonia dimer: extremely fluxional but still hydrogen bonded(Nature Communications, 2022-03-18) Aling, Jing; Szalewicz, Krzysztof; van der Avoird, AdIn the 1980s, Nelson, Fraser, and Klemperer (NFK) published an experimentally derived structure of the ammonia dimer dramatically different from the structure determined computationally, which led these authors to the question “Does ammonia hydrogen bond?". This question has not yet been answered satisfactorily. To answer it, we have developed an ab initio potential energy surface (PES) for this dimer at the limits of the current computational capabilities and performed essentially exact six-dimensional calculations of the vibration-rotation-tunneling (VRT) spectra of NH3-NH3 and ND3-ND3, obtaining an unprecedented agreement with experimental spectra. In agreement with other recent electronic structure calculations, the global minimum on the PES is in a substantially bent hydrogen-bonded configuration. Since the bottom of the PES is exceptionally flat, the dimer is extremely fluxional and the probability of finding it in configurations that are not hydrogen bonded is high. Nevertheless, the probability of hydrogen-bonded configurations is large enough to consider the ammonia dimer to be hydrogen bonded. We also show that NFK’s inference that the ammonia dimer is nearly rigid actually results from unusual cancellations between quantum effects that generate differences in spectra of different isotopologues.
- ItemBimetal–organic frameworks derived tuneable Co nanoparticles embedded in porous nitrogen-doped carbon nanorods as high-performance electromagnetic wave absorption materials(Journal of Materials Chemistry C, 2021-05-04) Pan, Jiannan; Yang, Huadong; Hong, Qu; Wen, Hui-Min; Xiao, John Q.; Hu, JunThe in situ pyrolysis of metal–organic-frameworks (MOFs) is an effective strategy to prepare magnetic metal nanoparticle (NP) doped porous carbon materials. These composite materials have shown great potential as high performance electromagnetic wave (EMW) absorption materials. So far, the precise control of composite composition and structure has remained a major challenge in constructing highly porous composites with uniformly distributed NPs. In this work, we report a facile route to synthesize tuneable Co NPs embedded in porous nitrogen-doped carbon (Co/NC) nanorods through the direct thermolysis of the bimetal–organic framework (CoZn–ZIF) precursor. By adjusting the proportion of Co2+ in the MOF precursor, the content and distribution of Co NPs in the composite absorber change accordingly. When the molar ratio between Co2+ and Zn2+ is 3 : 1, the carbonized composites exhibit the largest external surface area and the best EMW absorption performance. With a filler mass loading of merely 15 wt%, the minimum reflection loss (RLmin) reaches −52.3 dB at 10.1 GHz with a thin layer thickness of 2.5 mm. The largest effective absorption bandwidth (EAB) of 5.0 GHz (11.1–16.1 GHz) is achieved in a 2.0 mm thick sample. The qualified bandwidth can be up to 14.5 GHz (3.5–18.0 GHz) with the integrated thickness from 1.0 mm to 5.5 mm. The enhanced conductive/magnetic losses, strong interfacial/dipolar/defect polarization, hierarchical pore structure and the geometric effect endow the Co/NC absorber with improved impedance matching and enhanced attenuation of EMW. This work provides a good direction for the future study of MOF-derived lightweight and efficient EMW absorbing materials.
- ItemCentrifugal breakout reconnection as the electron acceleration mechanism powering the radio magnetospheres of early-type stars(Monthly Notices of the Royal Astronomical Society, 2022-04-27) Owocki, S. P.; Shultz, M. E.; ud-Doula, A.; Chandra, P.; Das, B.; Leto, P.Magnetic B-stars often exhibit circularly polarized radio emission thought to arise from gyrosynchrotron emission by energetic electrons trapped in the circumstellar magnetosphere. Recent empirical analyses show that the onset and strength of the observed radio emission scale with both the magnetic field strength and the stellar rotation rate. This challenges the existing paradigm that the energetic electrons are accelerated in the current sheet between opposite-polarity field lines in the outer regions of magnetized stellar winds, which includes no role for stellar rotation. Building on recent success in explaining a similar rotation-field dependence of H α line emission in terms of a model in which magnetospheric density is regulated by centrifugal breakout (CBO), we examine here the potential role of the associated CBO-driven magnetic reconnection in accelerating the electrons that emit the observed gyrosynchrotron radio. We show in particular that the theoretical scalings for energy production by CBO reconnection match well the empirical trends for observed radio luminosity, with a suitably small, nearly constant conversion efficiency ϵ ≈ 10−8. We summarize the distinct advantages of our CBO scalings over previous associations with an electromotive force, and discuss the potential implications of CBO processes for X-rays and other observed characteristics of rotating magnetic B-stars with centrifugal magnetospheres.
- ItemCrystal Structure Predictions for 4-Amino-2,3,6-trinitrophenol Using a Tailor-Made First-Principles-Based Force Field(Crystal Growth and Design, 2022-01-24) Metz, Michael P.; Shahbaz, Muhammad; Song, Hongxing; Vogt-Maranto, Leslie; Tuckerman, Mark E.; Szalewicz, KrzysztofPredictions of crystal structures from first-principles electronic structure calculations and molecular simulations have been performed for an energetic molecule, 4-amino-2,3,6-trinitrophenol. This physics-based approach consists of a series of steps. First, a tailor-made two-body potential energy surface (PES) was constructed with recently developed software, autoPES, using symmetry-adapted perturbation theory based on a density-functional theory description of monomers [SAPT(DFT)]. The fitting procedure ensures asymptotic correctness of the PES by employing a rigorous asymptotic multipole expansion, which seamlessly integrates with SAPT(DFT) interaction energies. Next, crystal structure prediction (CSP) was performed by generating possible crystal structures with rigid molecules, minimizing these structures using the SAPT(DFT) force field, and running isothermal–isobaric molecular dynamics (MD) simulations with flexible molecules based on the tailor-made SAPT(DFT) intermolecular force field and a generic/SAPT(DFT) intramolecular one. This workflow led to the experimentally observed structure being identified as one of the forms with the lowest lattice energy, demonstrating the success of a first-principles, bottom-up approach to CSP. Importantly, we argue that the accuracy of the intermolecular potential, here the SAPT(DFT)-based potential, is determinative of the crystal structure, while generic/SAPT(DFT) force fields can be used to represent the intramolecular potential. This force field approach simplifies the CSP workflow, without significantly compromising the accuracy of the prediction.
- ItemDetection of astrophysical tau neutrino candidates in IceCube(The European Physical Journal C, 2022-11-15) IceCube Collaboration; Abbasi, R.; Ackermann, M.; Adams, J.; et al.High-energy tau neutrinos are rarely produced in atmospheric cosmic-ray showers or at cosmic particle accelerators, but are expected to emerge during neutrino propagation over cosmic distances due to flavor mixing. When high energy tau neutrinos interact inside the IceCube detector, two spatially separated energy depositions may be resolved, the first from the charged current interaction and the second from the tau lepton decay. We report a novel analysis of 7.5 years of IceCube data that identifies two candidate tau neutrinos among the 60 “High-Energy Starting Events” (HESE) collected during that period. The HESE sample offers high purity, all-sky sensitivity, and distinct observational signatures for each neutrino flavor, enabling a new measurement of the flavor composition. The measured astrophysical neutrino flavor composition is consistent with expectations, and an astrophysical tau neutrino flux is indicated at 2.8σ significance.
- ItemDirect detection of ultralight dark matter bound to the Sun with space quantum sensors(Nature Astronomy, 2022-12-05) Tsai, Yu-Dai; Eby, Joshua; Safronova, Marianna S.Recent advances in quantum sensors, including atomic clocks, enable searches for a broad range of dark matter candidates. The question of the dark matter distribution in the Solar system critically affects the reach of dark matter direct detection experiments. Partly motivated by the NASA Deep Space Atomic Clock and the Parker Solar Probe, we show that space quantum sensors present new opportunities for ultralight dark matter searches, especially for dark matter states bound to the Sun. We show that space quantum sensors can probe unexplored parameter space of ultralight dark matter, covering theoretical relaxion targets motivated by naturalness and Higgs mixing. If a two-clock system were able to make measurements on the interior of the solar system, it could probe this highly sensitive region directly and set very strong constraints on the existence of such a bound-state halo in our solar system. We present sensitivity projections for space-based probes of ultralight dark matter, which couples to electron, photon and gluon fields, based on current and future atomic, molecular and nuclear clocks.
- ItemDirect probing of strong magnon–photon coupling in a planar geometry(Quantum Science and Technology, 2022-10-31) Kaffash, Mojtaba T.; Wagle, Dinesh; Rai, Anish; Meyer, Thomas; Xiao, John Q.; Jungfleisch, M. BenjaminWe demonstrate direct probing of strong magnon–photon coupling using Brillouin light scattering (BLS) spectroscopy in a planar geometry. The magnonic hybrid system comprises a split-ring resonator loaded with epitaxial yttrium iron garnet thin films of 200 nm and 2.46 μm thickness. The BLS measurements are combined with microwave spectroscopy measurements where both biasing magnetic field and microwave excitation frequency are varied. The cooperativity for the 200 nm-thick YIG films is 1.1, and larger cooperativity of 29.1 is found for the 2.46 μm-thick YIG film. We show that BLS is advantageous for probing the magnonic character of magnon–photon polaritons, while microwave absorption is more sensitive to the photonic character of the hybrid excitation. A miniaturized, planar device design is imperative for the potential integration of magnonic hybrid systems in future coherent information technologies, and our results are a first stepping stone in this regard. Furthermore, successfully detecting the magnonic hybrid excitation by BLS is an essential step for the up-conversion of quantum signals from the microwave to the optical regime in hybrid quantum systems.
- ItemEffect of Strongly Magnetized Electrons and Ions on Heat Flow and Symmetry of Inertial Fusion Implosions(Physical Review Letters, 2022-05-11) Bose, A.; Peebles, J.; Walsh, C. A.; Frenje, J. A.; Kabadi, N. V.; Adrian, P. J.; Sutcliffe, G. D.; Johnson, M. Gatu; Frank, C. A.; Davies, J. R.; Betti, R.; Glebov, V. Yu.; Marshall, F. J.; Regan, S. P.; Stoeckl, C.; Campbell, E. M.; Sio, H.; Moody, J.; Crilly, A.; Appelbe, B. D.; Chittenden, J. P.; Atzeni, S.; Barbato, F.; Forte, A.; Li, C. K.; Seguin, F. H.; Petrasso, R. D.This Letter presents the first observation on how a strong, 500 kG, externally applied B field increases the mode-two asymmetry in shock-heated inertial fusion implosions. Using a direct-drive implosion with polar illumination and imposed field, we observed that magnetization produces a significant increase in the implosion oblateness (a 2.5× larger P2 amplitude in x-ray self-emission images) compared with reference experiments with identical drive but with no field applied. The implosions produce strongly magnetized electrons (ωeτe≫1) and ions (ωiτi>1) that, as shown using simulations, restrict the cross field heat flow necessary for lateral distribution of the laser and shock heating from the implosion pole to the waist, causing the enhanced mode-two shape.
- ItemElectroweak monopoles and magnetic dumbbells in grand unified theories(Physical Review D, 2021-05-20) Lazarides, G.; Shafi, Q.We use the SU(5) model to show the presence in grand unified theories of an electroweak monopole and a magnetic dumbbell (“meson”) made up of a monopole-antimonopole pair connected by a Z-magnetic flux tube. The monopole is associated with the spontaneous breaking of the weak SU(2)L gauge symmetry by the induced vacuum expectation value of a heavy scalar SU(2)L triplet with zero weak hypercharge contained in the adjoint Higgs 24-plet. This monopole carries a Coulomb magnetic charge of (3/4)(2π/e) as well as Z-magnetic charge, where 2π/e denotes the unit Dirac magnetic charge. Its total magnetic charge is √3/8(4π/e), which is in agreement with the Dirac quantization condition. The monopole weighs about 700 GeV, but because of the attached Z-magnetic tube it exists, together with the antimonopole, in a magnetic dumbbell configuration whose mass is expected to lie in the TeV range. The presence of these topological structures in SU(5) and SO(10) and in their supersymmetric extensions provides an exciting new avenue for testing these theories in high-energy colliders.
- ItemEnergy transfer in reconnection and turbulence(Physical Review E, 2021-12-21) Adhikari, S.; Parashar, T. N.; Shay, M. A.; Matthaeus, W. H.; Pyakurel, P. S.; Fordin, S.; Stawarz, J. E.; Eastwood, J. P.Reconnection and turbulence are two of the most commonly observed dynamical processes in plasmas, but their relationship is still not fully understood. Using 2.5D kinetic particle-in-cell simulations of both strong turbulence and reconnection, we compare the cross-scale transfer of energy in the two systems by analyzing the generalization of the von Kármán Howarth equations for Hall magnetohydrodynamics, a formulation that subsumes the third-order law for steady energy transfer rates. Even though the large scale features are quite different, the finding is that the decomposition of the energy transfer is structurally very similar in the two cases. In the reconnection case, the time evolution of the energy transfer also exhibits a correlation with the reconnection rate. These results provide explicit evidence that reconnection dynamics fundamentally involves turbulence-like energy transfer.
- ItemFactors influencing hydrogen peroxide versus water inclusion in molecular crystals(Physical Chemistry Chemical Physics, 2022-04-28) Wiscons, Ren A.; Nikhar, Rahul; Szalewicz, Krzysztof; Matzger, Adam J.Hydrate formation is often unavoidable during crystallization, leading to performance degradation of pharmaceuticals and energetics. In some cases, water molecules trapped within crystal lattices can be substituted for hydrogen peroxide, improving the solubility of drugs and detonation performance of explosives. The present work compares hydrates and hydrogen peroxide solvates in two ways: (1) analyzing structural motifs present in crystal structures accessed from the Cambridge Structural Database and (2) developing potential energy surfaces for water and hydrogen peroxide interacting with functional groups of interest at geometries relevant to the solid state. By elucidating fundamental differences in local interactions that can be formed with molecules of hydrogen peroxide and/or water, the analyses presented here provide a foundation for the design and selection of candidate molecules for the formation of hydrogen peroxide solvates.
- ItemInner shell excitation by strong field laser rescattering: optimal laser conditions for high energy recollision(Journal of the Optical Society of America B, 2021-11-15) Kelley, L.; Germain, Z.; Jones, E. C.; Milliken, D.; Walker, Barry C.We address the challenge of finding the optimal laser intensity and wavelength to drive high-energy, strong field rescattering and report the maximum yields of K-shell and LI-shell hole creation. Surprisingly, our results show laser-driven rescattering is able to create inner shell holes in all atoms from lithium to uranium with the interaction spanning from the deep IR to x-ray free electron laser sources. The calculated peak rescattering follows a simple scaling with the atomic number and laser wavelength. The results show it is possible to describe the ideal laser intensity and wavelength for general high-energy laser rescattering processes.
- ItemLaser spectroscopy of the y7PoJ states of Cr I(Physical Review A, 2022-03-16) Norrgard, E. B.; Barker, D. S.; Eckel, S. P.; Porsev, S. G.; Cheung, C.; Kozlov, M. G.; Tupitsyn, I. I.; Safronova, M. S.Here we report measured and calculated values of decay rates of the 3d4(5D)4s4p(3Po)y7Po2,3,4 states of Cr i. The decay rates are measured using time-correlated single-photon counting with roughly 1% total uncertainty. In addition, the isotope shifts for transitions between these states and the ground state are measured by laser induced fluorescence to roughly 0.5% uncertainty. The decay rate calculations are carried out by a hybrid approach that combines configuration interaction and the linearized coupled-cluster method (CI+all-order method). The measurements provide a much needed precision benchmark for testing the accuracy of the CI+all-order approach for such complicated systems with six valence electrons, allowing us to significantly expand its applicability. These measurements also demonstrate operation of a cryogenic buffer gas beam source for future cold molecule experiments.
- ItemLight and microwave driven spin pumping across FeGaB–BiSb interface(Physical Review Materials, 2021-12-16) Sharma, Vinay; Wu, Weipeng; Bajracharya, Prabesh; To, Duy Quang; Johnson, Anthony; Janotti, Anderson; Bryant, Garnett W.; Gundlach, Lars; Jungfleisch, M. Benjamin; Budhani, Ramesh C.Three-dimensional (3D) topological insulators (TIs) with large spin Hall conductivity have emerged as potential candidates for spintronic applications. Here, we report spin to charge conversion in bilayers of amorphous ferromagnet (FM) Fe78Ga13B9 (FeGaB) and 3D TI Bi85Sb15 (BiSb) activated by two complementary techniques: spin pumping and ultrafast spin-current injection. DC magnetization measurements establish the soft magnetic character of FeGaB films, which remains unaltered in the heterostructures of FeGaB-BiSb. Broadband ferromagnetic resonance (FMR) studies reveal enhanced damping of precessing magnetization and large value of spin mixing conductance (5.03×1019m–2) as the spin angular momentum leaks into the TI layer. Magnetic field controlled bipolar DC voltage generated across the TI layer by inverse spin Hall effect is analyzed to extract the values of spin Hall angle and spin diffusion length of BiSb. The spin pumping parameters derived from the measurements of the femtosecond light-pulse-induced terahertz emission are consistent with the result of FMR. The Kubo-Bastin formula and tight-binding model calculations shed light on the thickness-dependent spin-Hall conductivity of the TI films, with predictions that are in remarkable agreement with the experimental data. Our results suggest that room temperature deposited amorphous and polycrystalline heterostructures provide a promising platform for creating novel spin orbit torque devices.
- ItemMeasurement of the tune-out wavelength for 133Cs at 880 nm(Physical Review A, 2021-11-22) Ratkata, Apichayaporn; Gregory, Philip D.; Innes, Andrew D.; Matthies, Jonas A.; McArd, Lewis A.; Mortlock, Jonathan M.; Safronova, M. S.; Bromley, Sarah L.; Cornish, Simon L.We perform a measurement of the tune-out wavelength, λ0, between the D1, 62S1/2→62P1/2, and D2, 62S1/2→62P3/2, transitions for 133Cs in the ground hyperfine state (F=3,mF=+3). At λ0, the frequency-dependent scalar polarizability is zero leading to a zero scalar ac Stark shift. We measure the polarizability as a function of wavelength using Kapitza-Dirac scattering of a 133Cs Bose-Einstein condensate in a one-dimensional optical lattice, and determine the tune-out wavelength to be λ0=880.21790(40)stat(8)sys nm. From this measurement we determine the ratio of reduced matrix elements to be ∣∣⟨6P3/2∥d∥6S1/2⟩∣∣2/∣∣⟨6P1/2∥d∥6S1/2⟩∣∣2=1.9808(2). This represents an improvement of a factor of 10 over previous results derived from excited-state lifetime measurements. We use the present measurement as a benchmark test of high-precision theory.
- ItemMechanical Energy Deposition in Cool Star Atmospheres: Resonant Coupling to Coronal Loops in M Dwarfs(The Astrophysical Journal, 2021-11-29) Mullan, D. J.The efficiency of coronal heating ε(cor) in a star can be quantified by LX/Lbol, i.e., the ratio of X-ray luminosity to bolometric luminosity. The efficiency of chromospheric heating in the same star ε(chr) is typically assumed to be proportional to L(Hα)/Lbol or L(Ca K)/Lbol where the lines Hα and Ca K are often the two strongest emission lines in the visible spectrum: the constant of proportionality (η = ε(chr)/[L(Hα)/Lbol] > 1) includes contributions from many other lines emitted by the chromosphere. In the case of the quiet Sun, it has been known for decades that, in the Sun, the efficiency of chromospheric heating is larger by a factor of ε(chr)/ε(cor) > 10 than the efficiency of coronal heating. Over the intervening years, data pertaining to ε(cor) and ε(chr) have been estimated for an increasingly large sample of main-sequence stars with spectral types later than the Sun. These data suggest that among M dwarfs, the efficiency ratio ε(chr)/ε(cor) may in some stars become smaller than in the solar case. The effect of this is such that the value of ε(cor) may become comparable to the value of ε(chr). Here, we seek to understand why coronal heating may be >10 times more efficient (relative to chromospheric heating) in certain M dwarfs than in the Sun. Using data on coronal loop properties in flaring stars, we examine the hypothesis that in M dwarfs, the enhanced efficiency of coronal heating may be related to resonant coupling between coronal loops and the source of mechanical energy in the convection zone.
- ItemMOBSTER – VI. The crucial influence of rotation on the radio magnetospheres of hot stars(Monthly Notices of the Royal Astronomical Society, 2022-04-27) Shultz, M. E.; Owocki, S. P.; ud-Doula, A.; Biswas, A.; Bohlender, D.; Chandra, P.; Das, B.; David-Uraz, A.; Khalack, V.; Kochukhov, O.; Landstreet, J. D.; Leto, P.; Monin, D.; Neiner, C.; Rivinius, Th.; Wade, G. A.Numerous magnetic hot stars exhibit gyrosynchrotron radio emission. The source electrons were previously thought to be accelerated to relativistic velocities in the current sheet formed in the middle magnetosphere by the wind opening magnetic field lines. However, a lack of dependence of radio luminosity on the wind power, and a strong dependence on rotation, has recently challenged this paradigm. We have collected all radio measurements of magnetic early-type stars available in the literature. When constraints on the magnetic field and/or the rotational period are not available, we have determined these using previously unpublished spectropolarimetric and photometric data. The result is the largest sample of magnetic stars with radio observations that has yet been analysed: 131 stars with rotational and magnetic constraints, of which 50 are radio-bright. We confirm an obvious dependence of gyrosynchrotron radiation on rotation, and furthermore find that accounting for rotation neatly separates stars with and without detected radio emission. There is a close correlation between H α emission strength and radio luminosity. These factors suggest that radio emission may be explained by the same mechanism responsible for H α emission from centrifugal magnetospheres, i.e. centrifugal breakout (CBO), however, while the H α-emitting magnetosphere probes the cool plasma before breakout, radio emission is a consequence of electrons accelerated in centrifugally driven magnetic reconnection.
- ItemNew Measurement Resolves Key Astrophysical Fe XVII Oscillator Strength Problem(Physical Review Letters, 2022-12-05) Kühn, Steffen; Cheung, Charles; Oreshkina, Natalia S.; Steinbrügge, René; Togawa, Moto; Bernitt, Sonja; Berger, Lukas; Buck, Jens; Hoesch, Moritz; Seltmann, Jörn; Trinter, Florian; Keitel, Christoph H.; Kozlov, Mikhail G.; Porsev, Sergey G.; Gu, Ming Feng; Porter, F. Scott; Pfeifer, Thomas; Leutenegger, Maurice A.; Harman, Zoltán; Safronova, Marianna S.; López-Urrutia, José R. Crespo; Shah, ChintanOne of the most enduring and intensively studied problems of x-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two Fe XVII transitions of crucial value for plasma diagnostics, dubbed 3C and 3D. We unravel this conundrum at the PETRA III synchrotron facility by increasing the resolving power 2.5 times and the signal-to-noise ratio thousandfold compared with our previous work. The Lorentzian wings had hitherto been indistinguishable from the background and were thus not modeled, resulting in a biased line-strength estimation. The present experimental oscillator-strength ratio Rexp=f3C/f3D=3.51(2)stat(7)sys agrees with our state-of-the-art calculation of Rth=3.55(2), as well as with some previous theoretical predictions. To further rule out any uncertainties associated with the measured ratio, we also determined the individual natural linewidths and oscillator strengths of 3C and 3D transitions, which also agree well with the theory. This finally resolves the decades-old mystery of Fe XVII oscillator strengths.
- ItemObservation of nonlinear planar Hall effect in magnetic-insulator–topological-insulator heterostructures(Physical Review B, 2022-10-10) Wang, Yang; Mambakkam, Sivakumar V.; Huang, Yue-Xin; Wang, Yong; Ji, Yi; Xiao, Cong; Yang, Shengyuan A.; Law, Stephanie A.; Xiao, John Q.Interfacing topological insulators (TIs) with magnetic insulators (MIs) have been widely used to study the interaction between topological surface states and magnetism. Previous transport studies typically interpret the suppression of weak antilocalization or appearance of the anomalous Hall effect as signatures of the magnetic proximity effect (MPE) imposed to TIs. Here, we report the observation of the nonlinear planar Hall effect (NPHE) in Bi2Se3 films grown on MI thulium and yttrium-iron-garnet (TmIG and YIG) substrates, which is an order of magnitude larger than that in Bi2Se3 grown on nonmagnetic gadolinium-gallium-garnet (GGG) substrate. The nonlinear Hall resistance in TmIG/Bi2Se3 depends linearly on the external magnetic field, while that in YIG/Bi2Se3 exhibits an extra hysteresis loop around zero field. The magnitude of the NPHE is found to scale inversely with carrier density. We speculate that the observed NPHE is related to the MPE-induced exchange gap opening and out-of-plane spin textures in the TI surface states, which may be used as an alternative transport signature of the MPE in MI/TI heterostructures.
- ItemPrecision Calculation of Hyperfine Constants for Extracting Nuclear Moments of 229Th(Physical Review Letters, 2021-12-17) Porsev, S. G.; Safronova, M. S.; Kozlov, M. G.Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants, with theoretical uncertainties directly affecting the resulting uncertainties of the nuclear moments. In this work, we improve the precision of such a method by including for the first time an iterative solution of equations for the core triple cluster amplitudes into the relativistic coupled-cluster method, with large-scale complete basis sets. We carried out calculations of the energies and magnetic dipole and electric quadrupole hyperfine structure constants for the low-lying states of 229Th3+ in the framework of such a relativistic coupled-cluster single double triple method. We present a detailed study of various corrections to all calculated properties. Using the theory results and experimental data, we found the nuclear magnetic dipole and electric quadrupole moments to be μ=0.366(6)μN and Q=3.11(2) eb, respectively, and reduce the uncertainty of the quadrupole moment by a factor of 3. The Bohr-Weisskopf effect of the finite nuclear magnetization is investigated, with bounds placed on the deviation of the magnetization distribution from the uniform one.