Superconductivity in compressed lithium is observed by magnetic susceptibility and electrical resistivity measurements. A superconducting critical temperature (Tc) is found ranging from 9 to 16 kelvin at 23 to 80 gigapascals. The pressure dependence of Tc suggests multiple phase transitions, consistent with theoretical predictions and reported x-ray diffraction results. The observed values for Tc are much lower than those theoretically predicted, indicating that more sophisticated theoretical treatments similar to those proposed for metallic hydrogen may be required to understand superconductivity in dense phases of lithium.

Magnetic skyrmions are particle-like magnetization configurations which can be found in materials with broken inversion symmetry. Their topological nature allows them to circumvent around random pinning sites or impurities as they move within the magnetic layer, which makes them interesting as information carriers in memory devices. However, when the skyrmion is driven by a current, a Magnus force is generated which leads to the skyrmion moving away from the direction of the conduction electron flow. The deflection poses a serious problem to the realization of skyrmion-based devices, as it leads to skyrmion annihilation at the film edges. Here, we show that it is possible to guide the movement of the skyrmion and prevent it from annihilating by surrounding and compressing the skyrmion with strong local potential barriers. The compressed skyrmion receives higher contribution from the spin transfer torque, which results in the significant increase of the skyrmion speed.

Superconductors Superconductors D 8000Superconductivity in Dense Lithium. -As revealed by magnetic susceptibility and electrical resistivity measurements, compressed Li shows superconductivity with a critical temperature T C ranging from 9 to 16 K at 23 to 80 GPa. The observed T C values are much lower than those predicted theoretically, indicating that more sophisticated theoretical treatments may be required to understand superconductivity in dense phases of Li. -(STRUZHKIN*, V. V.; EREMETS, M. I.; GAN, W.; MAO, H.-K.; HEMLEY, R.

Despite the inefficiencies associated with current-induced spin torques, they remain the predominant mode of skyrmion propulsion. In this work, we demonstrate numerically that skyrmions can be transported much more efficiently with a voltage-controlled magnetic anisotropy (VCMA) gradient. An analytical model was developed to understand the underlying skyrmion dynamics on a track under the VCMA conditions. Our calculations reveal that the repulsive skyrmion-edge interaction not only prevents the skyrmion from annihilating but also generates most of the skyrmion propulsion. A multiplexed array of gate electrodes can be used to create discrete anisotropy gradients over a long distance, leading to the formation of a series of translatable skyrmion potential wells. Due to the strong confining potentials, skyrmions are transported at a 70% higher packing density. Finally, we demonstrated that this form of skyrmion propulsion can also be implemented on almost any 2D geometry, providing improved versatility over current-induced methods.

We report on a highly efficient magneto-actuated cancer cell apoptosis method using a biaxial pulsed magnetic field configuration, which maximizes the induced magnetic torque. The light transmissivity dynamics show that the biaxial magnetic field configuration can actuate the magnetic nanoparticles with higher responsiveness over a wide range of frequencies as compared to uniaxial field configurations. Its efficacy was demonstrated in in vitro cell destruction experiments with a greater reduction in cell viability. Magnetic nanoparticles with high aspect ratios were also found to form a triple vortex magnetization at remanence which increases its low field susceptibility. This translates to a larger magneto-mechanical actuated force at low fields and 12% higher efficacy in cell death as compared to low aspect ratio nanoparticles.

Current-driven skyrmions drift from the intended direction of motion in a thin magnetic film due to the presence of the Magnus force and are annihilated upon reaching the film edge. This paper proposes two methods to engineer a 1D potential well to confine the skyrmion motion in the center region of nanowires and thus preventing annihilation. By patterning the magnetic anisotropy of the film or by adding a layer of magnetic material at the edges, the barrier height and width of the potential well can be controlled. Magnetic skyrmions in such nanowires can then be guided to traverse only along the axis of the nanowire, even in nanowires with steep bends. In addition, we also report a compression mechanism where the skyrmion size and separation distance can be reduced by modifying the potential well, thus increasing the skyrmion packing density in a nanowire. The guided motion and high skyrmion density made possible by our proposed methods will allow for the realization of high density skyrmion based memory.Index Terms-Magnetic skyrmions, micromagnetic simulations, perpendicular magnetic anisotropy, spin structures.

We report on the influence of pinning potentials on current-driven skyrmion dynamics and demonstrate that skyrmions can be gated via either magnetic or electric fields. When encountering pinning potentials, skyrmions are well known to simply skirt around them. However, we show that skyrmions can be depinned much more easily when their driving force is oriented against the pinning site rather that the intuitive option of being oriented away. This observation can be exploited together with the normally undesirable Magnus force for the creation of a skyrmion diode. The phenomenon is explained by the increased skyrmion compression resulting from the spin transfer torque opposing the repulsive potential. The smaller skyrmion size then experiences a reduced pinning potential. For practical low-power device applications, we show that the same skyrmion compression can be recreated by applying either a magnetic or electric field. Our analysis provides an insight on the skyrmion dynamics and manipulation that is critical for the realization of skyrmion-based transistors and low-power memory.

The ability to control or manipulate the pathways leading to cell death plays a pivotal role in cancer treatment. We demonstrate magneto-actuation of magnetic nanoparticles (MNPs) to induce different cell death signaling pathways, exemplifying the intricate interplay between apoptosis and necrosis. In vitro cell experiments show the cell viabilities decreases with increasing field strength and is lower in cells treated with low aspect ratio MNPs. In a strong vertical magnetic field gradient, the MNPs were able to apply sufficient force on the cell to trigger the intracellular pathway for cell apoptosis, thus significantly reducing the cell viability. The quantification of apoptotic and necrotic cell populations by fluorescence dual staining attributed the cell death mechanism to be predominantly apoptosis in a magnetic field gradient. In contrast, the MNPs in an alternating magnetic field gradient can effectively rupture the cell membrane leading to higher lactate dehydrogenase leakage and lower cell viability, proving to be an effective induction of cell death via necrosis.