Uniquely in Cu 2 OSeO 3 , the Skyrmions, which are topologically protected magnetic spin vortexlike objects, display a magnetoelectric coupling and can be manipulated by externally applied electric (E) fields. Here, we explore the E-field coupling to the magnetoelectric Skyrmion lattice phase, and study the response using neutron scattering. Giant E-field induced rotations of the Skyrmion lattice are achieved that span a range of ∼25°. Supporting calculations show that an E-field-induced Skyrmion distortion lies behind the lattice rotation. Overall, we present a new approach to Skyrmion control that makes no use of spin-transfer torques due to currents of either electrons or magnons. [12,13]. All have the chiral-cubic space group P2 1 3, a weak magnetocrystalline anisotropy, and common phase diagrams with a helimagnetic ground state. Despite these similarities, the diverse transport properties lead to material specific mechanisms for Skyrmion manipulation and the associated dynamics. In the well-studied itinerant compounds, spin-transfer torques (STTs) exerted by the conduction electrons of an ultralow current density, j ≲ 10 6 A·m −2 drive the Skyrmion motion [5,[14][15][16][17][18][19]. More generally, in both MnSi and insulating Cu 2 OSeO 3 , Skyrmion lattice (SKL) rotations are observed to be driven by STTs exerted by the magnon currents induced by a thermal gradient [20]. Even though electric currents and thermal gradients have been established to generate Skyrmion motion, it remains vital to find new control mechanisms which may lead to further efficient Skyrmion-based functionalities.In the insulating SKL host compounds, the chiral lattice promotes a magnetoelectric (ME) coupling between electric (E) and magnetic orders which can be expected to lie at the heart of new Skyrmion control paradigms. The use of ME coupling for Skyrmion manipulation is also attractive for applications since losses due to Joule heating are negligible. Presently, however, open questions remain concerning the basic understanding of how an applied E field can manipulate the Skyrmion spin texture. To address this issue, we have used small-angle neutron scattering (SANS) to study the giant E-field-induced SKL rotations generated in a bulk sample of ME Cu 2 OSeO 3 . Surprisingly, the rotations saturate at an angle dependent on both the size and sign of the E field. With supporting calculations, we explain our observations, and show that an E-field-induced Skyrmion distortion leads to the observed rotations. This amounts to a new approach for Skyrmion control that does not require STTs.In Cu 2 OSeO 3 , the ME coupling exists in all magnetic phases [12,[21][22][23][24][25][26][27][28], and is generated by the d-p hybridization mechanism [12,24,29,30]. This mechanism dictates a particular ME coupling anisotropy; for a magnetic field μ 0 H∥½110 or [111], an electric polarization P emerges ∥½001 or [111], respectively [24]. In our experiments, we chose E∥½111 (which corresponds to a negative applied voltage) or ∥½111 (positive voltage). T...

Small-angle neutron scattering has been employed to study the influence of applied electric (E-)fields on the skyrmion lattice in the chiral lattice magnetoelectric Cu(2)OSeO(3). Using an experimental geometry with the E-field parallel to the [111] axis, and the magnetic field parallel to the [11(-)0] axis, we demonstrate that the effect of applying an E-field is to controllably rotate the skyrmion lattice around the magnetic field axis. Our results are an important first demonstration for a microscopic coupling between applied E-fields and the skyrmions in an insulator, and show that the general emergent properties of skyrmions may be tailored according to the properties of the host system.

TitleAtomically precise graphene nanoribbon heterojunctions from a single molecular precursor AbstractThe rational bottom-up synthesis of atomically defined graphene nanoribbon (GNR)heterojunctions represents a key enabling technology for the design of nanoscale electronic devices. Synthetic strategies have thus far relied on the random copolymerization of two electronically distinctive molecular precursors to yield a segmented band structure within a GNR. Here we report the fabrication and electronic characterization of atomically precise GNR heterojunctions prepared through a late-stage functionalization of chevron GNRs obtained from a single precursor that features fluorenone substituents along the convex edges. Excitation of the GNR induces cleavage of sacrificial carbonyl groups at the GNR edge, thus giving rise to atomically well-defined heterojunctions comprised of segments of fluorenone GNR and unfunctionalized chevron GNR. The structure of fluorenone/unfunctionalized GNR heterojunctions was characterized using bond-resolved STM (BRSTM) which enables chemical bonds to be imaged via STM at T = 4.5 K. Scanning tunneling spectroscopy (STS) reveals that the band alignment across the interface yields a staggered gap Type II heterojunction and is consistent with first-principles calculations. Detailed spectroscopic and theoretical studies reveal that the band realignment at the interface between fluorenone and unfunctionalized chevron GNRs proceeds over a distance less than 1nm, leading to extremely large effective fields.

We present the electronic characterization of single-layer 1H-TaSe grown by molecular beam epitaxy using a combined angle-resolved photoemission spectroscopy, scanning tunneling microscopy/spectroscopy, and density functional theory calculations. We demonstrate that 3 × 3 charge-density-wave (CDW) order persists despite distinct changes in the low energy electronic structure highlighted by the reduction in the number of bands crossing the Fermi energy and the corresponding modification of Fermi surface topology. Enhanced spin-orbit coupling and lattice distortion in the single-layer play a crucial role in the formation of CDW order. Our findings provide a deeper understanding of the nature of CDW order in the two-dimensional limit.

The thermally induced cyclodehydrogenation reaction of 6,6'-bipentacene precursors on Au(111) yields peripentacene stabilized by surface interactions with the underlying metallic substrate. STM and atomic-resolution non-contact AFM imaging reveal rectangular flakes of nanographene featuring parallel pairs of zig-zag and armchair edges resulting from the lateral fusion of two pentacene subunits. The synthesis of a novel molecular precursor 6,6'-bipentacene, itself a synthetic target of interest for optical and electronic applications, is also reported. The scalable synthetic strategy promises to afford access to a structurally diverse class of extended periacenes and related polycyclic aromatic hydrocarbons as advanced materials for electronic, spintronic, optical, and magnetic devices.