Double-slit electron interferometers fabricated in high mobility two-dimensional electron gases are powerful tools for studying coherent wave-like phenomena in mesoscopic systems. However, they suffer from low visibility of the interference patterns due to the many channels present in each slit, and from poor sensitivity to small currents due to their open geometry. Moreover, these interferometers do not function in high magnetic fields--such as those required to enter the quantum Hall effect regime--as the field destroys the symmetry between left and right slits. Here we report the fabrication and operation of a single-channel, two-path electron interferometer that functions in a high magnetic field. This device is the first electronic analogue of the optical Mach-Zehnder interferometer, and opens the way to measuring interference of quasiparticles with fractional charges. On the basis of measurements of single edge state and closed geometry transport in the quantum Hall effect regime, we find that the interferometer is highly sensitive and exhibits very high visibility (62%). However, the interference pattern decays precipitously with increasing electron temperature or energy. Although the origin of this dephasing is unclear, we show, via shot-noise measurements, that it is not a decoherence process that results from inelastic scattering events.

We measured the phase evolution of electrons as they traverse a quantum dot (QD) formed in a two-dimensional electron gas that serves as a localized spin. The traversal phase, determined by embedding the QD in a double path electron interferometer and measuring the quantum interference of the electron wave functions manifested by conductance oscillation as a function of a weak magnetic field, evolved by pi radians, a range twice as large as theoretically predicted. As the correlation weakened, a gradual transition to the familiar phase evolution of a QD was observed. The specific phase evolution observed is highly sensitive to the onset of Kondo correlation, possibly serving as an alternative fingerprint of the Kondo effect.

All-electrical and programmable manipulations of ferromagnetic bits are highly pursued for the aim of high integration and low energy consumption in modern information technology. Methods based on the spin-orbit torque switching in heavy metal/ferromagnet structures have been proposed with magnetic field, and are heading toward deterministic switching without external magnetic field. Here we demonstrate that an in-plane effective magnetic field can be induced by an electric field without breaking the symmetry of the structure of the thin film, and realize the deterministic magnetization switching in a hybrid ferromagnetic/ferroelectric structure with Pt/Co/Ni/Co/Pt layers on PMN-PT substrate. The effective magnetic field can be reversed by changing the direction of the applied electric field on the PMN-PT substrate, which fully replaces the controllability function of the external magnetic field. The electric field is found to generate an additional spin-orbit torque on the CoNiCo magnets, which is confirmed by macrospin calculations and micromagnetic simulations.

For more than a decade, the electrical switching of ferromagnets (FMs) with perpendicular magnetic anisotropy (PMA), using spin-transfer torque (STT) and more recently spin-orbit torque (SOT), has underpinned the development of fast, low-power-consumption, and high-density spintronic devices. [1][2][3][4][5] In general, both the STT-and the SOT-induced switching of a FM layer require an injection of out-ofplane spin current from nearby layers. [6][7][8] For STT-induced FM switching, particularly, a spin-polarized current is generated in a magnetic tunneling junction structure when a charge current flows perpendicularly through the stacks, where another FM layer acts as a spin polarizer. [9] Thus, device instability issues arise since the tunneling barrier layer between the two FM layers is required to transmit large switching currents.The SOT-induced FM switching, on the other hand, circumvents this problem by using an in-plane switching current. Conventionally, a stack structure consisting of a strong spin-orbit coupling (SOC) layer and a FM layer is used, where an in-plane charge current gives rise to an out-of-plane pure spin current due to spin Hall effect in the SOC layer and/or Rashba effect from the perpendicular interfacial inversion asymmetry. [10][11][12][13] The resulting SOT-induced effective magnetic field is in-plane, hence an additional orthogonal in-plane magnetic field is required to realize deterministic switching of a PMA-FM. To date, several approaches for field-free SOT-induced PMA-FM switching have been proposed and demonstrated, such as switching using a polarized ferroelectric substrate induced in-plane spin current gradient, [14][15][16] a wedge oxide capping layer, [17] a tilted PMA layer, [18] a stack with coherent in-plane exchange field, [19][20][21][22][23] an interplay of SOT and STT, [24,25] an inplane-FM/normal metal/PMA-FM trilayer, [26] and a particular low symmetric WTe 2 semimetal. [27] However, the concomitant complexities of these approaches highlight the inherent limitation of the conventional SOT scheme utilizing external outof-plane spin current injection in a perpendicular asymmetric structure.Here, we demonstrate magnetic field-free deterministic current-induced magnetization switching in a PMA Pt/Co/ Pt trilayer subjected to local laser annealing. Without external magnetic field, the direction of current-induced magnetization switching is found to depend on the relative location and Current-induced magnetization switching by spin-orbit torque (SOT) holds considerable promise for next generation ultralow-power memory and logic applications. In most cases, generation of spin-orbit torques has relied on an external injection of out-of-plane spin currents into the magnetic layer, while an external magnetic field along the electric current direction is generally required for realizing deterministic switching by SOT. Here, deterministic current-induced SOT full magnetization switching by lateral spin-orbit torque in zero external magnetic field is reported. The Pt/Co/Pt magn...

We report the low-temperature magnetotransport behaviors of (Ga,Mn)As films with the nominal Mn concentration x larger than 10%. The ferromagnetic transition temperature TC can be enhanced to 191 K after postgrowth annealing (Ga,Mn)As with x=20%. The temperature Tm, corresponding to the resistivity minimum in the curve of resistivity versus temperature at temperature below TC, depends on Mn concentration, annealing condition, and magnetic field. Moreover, we find that the variable-range hopping may be the main conductive mechanism when temperature is lower than Tm.

We report on direct measurement of charge and its distribution in a Kondo correlated quantum dot (QD). A noninvasive potential-sensitive detector, in proximity with a QD, reveals that, although the conductance of the QD is significantly enhanced as it enters the Kondo regime, the average charge remains unaffected. This demonstrates the separation between spin and charge degrees of freedom. We find, however, under certain conditions, an abrupt redistribution of charge in the QD, taking place with an onset of Kondo correlation. This suggests a correlation between the spin and charge degrees of freedom.

Understanding ecological niches of major tick species and prevalent tick-borne pathogens is crucial for efficient surveillance and control of tick-borne diseases. Here we provide an up-to-date review on the spatial distributions of ticks and tick-borne pathogens in China. We map at the county level 124 tick species, 103 tick-borne agents, and human cases infected with 29 species (subspecies) of tick-borne pathogens that were reported in China during 1950−2018. Haemaphysalis longicornis is found to harbor the highest variety of tick-borne agents, followed by Ixodes persulcatus, Dermacentor nutalli and Rhipicephalus microplus. Using a machine learning algorithm, we assess ecoclimatic and socioenvironmental drivers for the distributions of 19 predominant vector ticks and two tick-borne pathogens associated with the highest disease burden. The model-predicted suitable habitats for the 19 tick species are 14‒476% larger in size than the geographic areas where these species were detected, indicating severe under-detection. Tick species harboring pathogens of imminent threats to public health should be prioritized for more active field surveillance.

Utilizing time-resolved Kerr rotation techniques, we have investigated the spin dynamics of a high mobility, low density two dimensional electron gas in a GaAs/Al 0.35 Ga 0.65 As heterostructure in dependence on temperature from 1.5 K to 30 K. It is found that the spin relaxation/dephasing time under a magnetic field of 0.5 T exhibits a maximum of 3.12 ns around 14 K, superimposed on an increasing background with rising temperature. The appearance of the maximum is ascribed to that at the temperature where the crossover from the degenerate to the nondegenerate regime takes place, electron-electron Coulomb scattering becomes strongest, and thus inhomogeneous precession broadening due to D'yakonov-Perel' (DP) mechanism becomes weakest. These results agree with the recent theoretical predictions [Zhou et al., PRB 75, 045305 (2007)], verifying the importance of electron-electron Coulomb scattering to electron spin relaxation/dephasing. PACS numbers: 72.25.Rb, 71.70.Ej, 78.47.jc In recent years, spin dynamics in semiconductors has attracted considerable attention because of its potential application in the spin-based devices. 1 The operation of these devices requires spin lifetime long enough to achieve storage, transport and processing of information. Therefore, a comprehensive understanding of spin relaxation mechanism is a key factor for the realization of these devices. It is generally accepted that the D'yakonov-Perel' (DP) mechanism is the leading spin relaxation/dephasing (R/D) mechanism in n-type zincblende semiconductors. 2 This is caused by an wavevector kdependent effective magnetic field Ω(k) from the bulk inversion asymmetry, 3 i.e., the Dresselhaus term, and/or the structure inversion asymmetry, 4 i.e., the Rashba term. The spin relaxation rate can be determined by τ −1 = Ω(k) 2 τ P (k), where τ P (k) is the momentum relaxation time. 5 As the electronelectron Coulomb scattering does not contribute to the momentum relaxation time τ p , it has long been widely believed that the electron-electron Coulomb scattering is irrelevant in the spin relaxation. 5,6,7,8,9,10,11 However, it was first pointed out by Wu and Ning 12 that in the presence of inhomogeneous broadening, any scattering, including the spin conserving electron-electron Coulomb scattering, can cause an irreversible spin relaxation and dephasing. This inhomogeneous broadening can be the energy-dependent g-factor, 12 the DP term, 13,14 and even the k-dependent spin diffusion along a spacial gradient. 15 In n-type GaAs quantum well, the importance of the electron-electron scattering to the spin relaxation was proved by Glazov and Ivchenko 16 by using perturbation theory and Weng and Wu 14 from a fully microscopic many-body approach. In a temperature-dependent experimental study of the spin relaxation in n-type (001) quantum wells, Harleyet al. indirectly verified the effects of the electron-electron scattering on spin relaxation. 17,18 Nevertheless, the importance of the Coulomb scattering to the spin relaxation/dephasing (R/D)has not yet been ...