Fuel-ion species dynamics in hydrodynamiclike shock-driven $\mathrm{DT}{}^3\mathrm{He}$-filled inertial confinement fusion implosion is quantitatively assessed for the first time using simultaneously measured $\mathrm{D}{}^3\mathrm{He}$ and DT reaction histories. These reaction histories are measured with the particle x-ray temporal diagnostic, which captures the relative timing between different nuclear burns with unprecedented precision ($\sim 10\mathrm{ps}$). The observed $50\pm 10\mathrm{ps}$ earlier $\mathrm{D}{}^3\mathrm{He}$ reaction history timing (relative to DT) cannot be explained by average-ion hydrodynamic simulations and is attributed to fuel-ion species separation between the D, T, and ${}^3\mathrm{He}$ ions during shock convergence and rebound. At the onset of the shock burn, inferred ${}^3\mathrm{He}/\mathrm{T}$ fuel ratio in the burn region using the measured reaction histories is much higher as compared to the initial gas-filled ratio. As T and ${}^3\mathrm{He}$ have the same mass but different charge, these results indicate that the charge-to-mass ratio plays an important role in driving fuel-ion species separation during strong shock propagation even for these hydrodynamiclike plasmas.

Electron temperature gradient (ETG)-driven turbulence, despite its ultrafine scale, is thought to drive significant thermal losses in magnetic fusion devices—but what role does it play in stellarators? The first numerical simulations of ETG turbulence for the Wendelstein 7-X stellarator, together with power balance analysis from its initial experimental operation phase, suggest that the associated transport should be negligible compared to other channels. The effect, we argue, originates essentially from the geometric constraint of multiple field periods, a generic feature of stellarators.

Three-dimensional topological insulators protected by both the time reversal (TR) and mirror symmetries were recently predicted and observed. Two-dimensional materials featuring this property and their potential for device applications have been less explored. We find that, in these systems, the spin polarization of edge states can be controlled with an external electric field breaking the mirror symmetry. This symmetry requires that the spin polarization is perpendicular to the mirror plane; therefore, the electric field induces spin-polarization components parallel to the mirror plane. Since this field preserves the TR topological protection, we propose a transistor model using the spin direction of protected edge states as a switch. In order to illustrate the generality of the proposed phenomena, we consider compounds protected by mirror planes parallel and perpendicular to the structure, e.g., ${\mathrm{Na}}_3\mathrm{Bi}$ and half-functionalized (HF) hexagonal compounds, respectively. For this purpose, we first construct a tight-binding effective model for the ${\mathrm{Na}}_3\mathrm{Bi}$ compound and predict that HF-honeycomb lattice materials are also dual topological insulators.

The quantum Hall effect (QHE) in a 3D Dirac semimetal thin film is attributed to either the quantum confinement induced bulk subbands or the Weyl orbits that connect the opposite surfaces via bulk Weyl nodes. However, it is still unknown whether the QHE based on the Weyl orbit can survive as the bulk Weyl nodes are gapped. Moreover, there are closed Fermi loops rather than open Fermi arcs on the Dirac semimetal surface, which can also host the QHE. Here we report the QHE in the 3D Dirac semimetal ${\mathrm{Cd}}_3{\mathrm{As}}_2$ nanoplate by tuning the gate voltage under a fixed 30 T magnetic field. The quantized Hall plateaus at odd filling factors are observed as a magnetic field along the [001] crystal direction, indicating a Berry’s phase $\pi$ from the topological surface states. Furthermore, even filling factors are observed when the magnetic field is along the [112] direction, indicating the $C_4$ rotational symmetry breaking and a topological phase transition. The results shed light on the understanding of QHE in 3D ${\mathrm{Cd}}_3{\mathrm{As}}_2$.

$1T-{\mathrm{TaS}}_2$ is a charge-density-wave (CDW) compound with a Mott-insulating ground state. The metallic state obtained by doping, substitution, or pulsed charge injection is characterized by an emergent CDW domain-wall network, while single domain walls can be found in the pristine Mott state. Here we study whether and how the single walls become metallic. Tunneling spectroscopy reveals partial suppression of the Mott gap and the presence of in-gap states strongly localized at the domain-wall sites. Using the real-space dynamical mean field theory description of the strongly correlated quantum-paramagnet ground state, we show that the local gap suppression follows from the increased hopping along the connected zigzag chain of lattice sites forming the domain wall. Furthermore, we show that full metallization is preempted by the splitting of the quasiparticle band into bonding and antibonding subbands due to the structural dimerization of the wall, explaining the presence of the in-gap states and the low density of states at the Fermi level.

Coherent control of individual molecular spins in nanodevices is a pivotal prerequisite for fulfilling the potential promised by molecular spintronics. By applying electric field pulses during time-resolved electron spin resonance measurements, we measure the sensitivity of the spin in several antiferromagnetic molecular nanomagnets to external electric fields. We find a linear electric field dependence of the spin states in ${\mathrm{Cr}}_7\mathrm{Mn}$, an antiferromagnetic ring with a ground-state spin of $S=1$, and in a frustrated ${\mathrm{Cu}}_3$ triangle, both with coefficients of about $2\mathrm{rad}{\mathrm{s}}^{-1}/\mathrm{V}{\mathrm{m}}^{-1}$. Conversely, the antiferromagnetic ring ${\mathrm{Cr}}_7\mathrm{Ni}$, isomorphic with ${\mathrm{Cr}}_7\mathrm{Mn}$ but with $S=1/2$, does not exhibit a detectable effect. We propose that the spin-electric field coupling may be used for selectively controlling individual molecules embedded in nanodevices.

We show that an inhomogeneity in the spin-transfer torques in a metallic ferromagnet under suitable conditions strongly amplifies incoming spin waves. Moreover, at nonzero temperatures the incoming thermally occupied spin waves will be amplified such that the region with inhomogeneous spin-transfer torques emits spin waves spontaneously, thus constituting a spin-wave laser. We determine the spin-wave scattering amplitudes for a simplified model and setup, and show under which conditions the amplification and lasing occurs. Our results are interpreted in terms of a so-called black-hole laser, and could facilitate the field of magnonics, which aims to utilize spin waves in logic and data-processing devices.

Two close parallel mirrors attract due to a small force (Casimir effect) originating from the quantum vacuum fluctuations of the electromagnetic field. These vacuum fluctuations can also induce motional forces exerted upon one mirror when the other one moves. Here, we consider an optomechanical system consisting of two vibrating mirrors constituting an optical resonator. We find that motional forces can determine noticeable coupling rates between the two spatially separated vibrating mirrors. We show that, by tuning the two mechanical oscillators into resonance, energy is exchanged between them at the quantum level. This coherent motional coupling is enabled by the exchange of virtual photon pairs, originating from the dynamical Casimir effect. The process proposed here shows that the electromagnetic quantum vacuum is able to transfer mechanical energy somewhat like an ordinary fluid. We show that this system can also operate as a mechanical parametric down-converter even at very weak excitations. These results demonstrate that vacuum-induced motional forces open up new possibilities for the development of optomechanical quantum technologies.

Trapped ions offer a pristine platform for quantum computation and simulation, but improving their coherence remains a crucial challenge. Here, we propose and analyze a new strategy to enhance the coherent interactions in trapped ion systems via parametric amplification of the ions’ motion—by squeezing the collective motional modes (phonons), the spin-spin interactions they mediate can be significantly enhanced. We illustrate the power of this approach by showing how it can enhance collective spin states useful for quantum metrology, and how it can improve the speed and fidelity of two-qubit gates in multi-ion systems, important ingredients for scalable trapped ion quantum computation. Our results are also directly relevant to numerous other physical platforms in which spin interactions are mediated by bosons.

We define the rigidity of a Feynman integral to be the smallest dimension over which it is nonpolylogarithmic. We prove that massless Feynman integrals in four dimensions have a rigidity bounded by $2(L-1)$ at $L$ loops provided they are in the class that we call marginal: those with $(L+1)D/2$ propagators in (even) $D$ dimensions. We show that marginal Feynman integrals in $D$ dimensions generically involve Calabi-Yau geometries, and we give examples of finite four-dimensional Feynman integrals in massless ${\phi }^4$ theory that saturate our predicted bound in rigidity at all loop orders.

A tunable plasma-based energy dechirper has been developed at FLASHForward to remove the correlated energy spread of a 681 MeV electron bunch. Through the interaction of the bunch with wakefields excited in plasma the projected energy spread was reduced from a FWHM of 1.31% to 0.33% without reducing the stability of the incoming beam. The experimental results for variable plasma density are in good agreement with analytic predictions and three-dimensional simulations. The proof-of-principle dechirping strength of $1.8\mathrm{GeV}/\mathrm{mm}/\mathrm{m}$ significantly exceeds those demonstrated for competing state-of-the-art techniques and may be key to future plasma wakefield-based free-electron lasers and high energy physics facilities, where large intrinsic chirps need to be removed.

The description of the local turbulent energy transfer and the high-resolution ion distributions measured by the Magnetospheric Multiscale mission together provide a formidable tool to explore the cross-scale connection between the fluid-scale energy cascade and plasma processes at subion scales. When the small-scale energy transfer is dominated by Alfvénic, correlated velocity, and magnetic field fluctuations, beams of accelerated particles are more likely observed. Here, for the first time, we report observations suggesting the nonlinear wave-particle interaction as one possible mechanism for the energy dissipation in space plasmas.

An empirical potential that has been widely used to perform molecular dynamics studies on the fracture behavior of FeP metallic glasses is shown to exhibit spinodal decomposition in the composition range commonly studied. The phosphorous segregation induces a transition from ductility to brittleness. During brittle fracture the atomically sharp crack tip propagates along a percolating path with higher P concentration. This embrittlement is observed to occur over a wide range of chemical compositions, and toughness decreases linearly with the degree of compositional segregation over the entire regime studied. Stable glass forming alloys that can be quenched at low quench rates do not, as a rule, exhibit such thermodynamically unstable behavior near to or above their glass transition temperatures. Hence, the microstructures exhibited in these simulations are unlikely to reflect the actual microstructures or fracture behaviors of the glassy alloys they seek to elucidate.

Weyl semimetals (WSMs) host charged Weyl fermions as emergent quasiparticles. We develop a unified analytical theory for the anomalous positive longitudinal magnetoconductivity (LMC) in a WSM, which bridges the gap between the classical and ultraquantum approaches. More interestingly, the LMC is found to exhibit periodic-in-$1/B$ quantum oscillations, originating from the oscillations of the nonequilibrium chiral chemical potential. The quantum oscillations, superposed on the positive LMC, are a remarkable fingerprint of a WSM phase with a chiral anomaly, whose observation is a valid criteria for identifying a WSM material. In fact, such quantum oscillations were already observed by several experiments.

We explore the superconducting phase diagram of the two-dimensional electron system at the ${\mathrm{LaAlO}}_3/\mathrm{SrTi}{\mathrm{O}}_3$ interface by monitoring the frequencies of the cavity modes of a coplanar waveguide resonator fabricated in the interface itself. We determine the phase diagram of the superconducting transition as a function of the temperature and electrostatic gating, finding that both the superfluid density and the transition temperature follow a dome shape but that the two are not monotonically related. The ground state of this two-dimensional electron system is interpreted as a Josephson junction array, where a transition from long- to short-range order occurs as a function of the electronic doping. The synergy between correlated oxides and superconducting circuits is revealed to be a promising route to investigate these exotic compounds, complementary to standard magnetotransport measurements.

We have systematically studied physical properties of $\mathrm{Ba}({\mathrm{Fe}}_{0.97}{\mathrm{Cr}}_{0.03}{)}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$, where superconductivity in ${\mathrm{BaFe}}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$ is fully suppressed by just 3% of Cr substitution of Fe. A quantum critical point is revealed at $x\sim 0.42$, where non-Fermi-liquid behaviors similar to those in ${\mathrm{BaFe}}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$ are observed. Neutron diffraction and inelastic neutron scattering measurements suggest that the quantum critical point is associated with the antiferromagnetic order, which is not of conventional spin-density-wave type as evidenced by the $\omega /T$ scaling of spin excitations. On the other hand, no divergence of low-temperature nematic susceptibility is observed when $x$ is decreased to 0.42 from higher doping level, demonstrating that there are no nematic quantum critical fluctuations. Our results suggest that non-Fermi-liquid behaviors in iron-based superconductors can be solely resulted from the antiferromagnetic quantum critical fluctuations, which cast doubts on the role of nematic fluctuations played in the normal-state properties in iron-based superconductors.

We propose a magnetic measurement method utilizing a patterned postsample aperture in a transmission electron microscope. While utilizing electron magnetic circular dichroism, the method circumvents previous needs to shape the electron probe to an electron vortex beam or astigmatic beam. The method can be implemented in standard scanning transmission electron microscopes by replacing the spectrometer entrance aperture with a specially shaped aperture, hereafter called a ventilator aperture. The proposed setup is expected to work across the whole range of beam sizes—from wide parallel beams down to atomic resolution magnetic spectrum imaging.

The highly strained conformation in dense molecular bottlebrushes (DB) has profound effects on the dynamics of these type of macromolecules. Understanding of such effects in both their linear and nonlinear viscoelastic responses is crucial for their design and processing. The nonlinear response of poly(1-octadecene), a highly entangled $\alpha$-olefin DB with linear side chains sixteen carbons long, is studied here and compared to the nonlinear response of a linear polyolefin (polypropylene) with equivalent linear viscoelastic response. We found that the DB shows remarkably larger extensional strain hardening (SH) and extensibility than the linear polyolefin. The strong SH is attributed to a strain-induced increase in friction drag between adjacent chains resulting from side-chain interdigitation and alignment perpendicular to the flow. The higher extensibility of DBs compared to linear counterparts has been predicted previously [Daniel et al., Nat. Mater. 15, 183 (2015)] and confirmed here for the first time in DB melts.