Semiconductor InSb nanowires are expected to provide an excellent material platform for the study of Majorana fermions in solid state systems. Here, we report on the realization of a Nb-InSb nanowire-Nb hybrid quantum device and the observation of a zero-bias conductance peak structure in the device. An InSb nanowire quantum dot is formed in the device between the two Nb contacts. Due to the proximity effect, the InSb nanowire segments covered by the superconductor Nb contacts turn to superconductors with a superconducting energy gap Δ(InSb) ∼ 0.25 meV. A tunable critical supercurrent is observed in the device in high back gate voltage regions in which the Fermi level in the InSb nanowire is located above the tunneling barriers of the quantum dot and the device is open to conduction. When a perpendicular magnetic field is applied to the devices, the critical supercurrent is seen to decrease as the magnetic field increases. However, at sufficiently low back gate voltages, the device shows the quasi-particle Coulomb blockade characteristics and the supercurrent is strongly suppressed even at zero magnetic field. This transport characteristic changes when a perpendicular magnetic field stronger than a critical value, at which the Zeeman energy in the InSb nanowire is E(z) ∼ Δ(InSb), is applied to the device. In this case, the transport measurements show a conductance peak at the zero bias voltage and the entire InSb nanowire in the device behaves as in a topological superconductor phase. We also show that this zero-bias conductance peak structure can persist over a large range of applied magnetic fields and could be interpreted as a transport signature of Majorana fermions in the InSb nanowire.

Designing nonprecious electrocatalysts with multiple active sites and prolonged durability in an integrated electrolyte toward water splitting is momentous for renewable energies being reserved in chemical fuels. Herein, we developed a method for synthesizing multimetallic hydroxide nanosheets by corroding nickel foam with chloride ions, which enabled the screening and discovery of various multimetallic hydroxide electrocatalysts toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). We discovered that Ni5Co3Mo–OH nanosheets exhibited electrocatalytic performances toward OER (η100 = 304  mV) and HER (η10 = 52  mV). Moreover, Ni5Co3Mo–OH can be employed as active bifunctional catalysts toward overall water splitting with a low cell voltage of 1.43 V at 10 mA·cm–2 (1.60 V at 100 mA·cm–2) and stable operation for 100 h (100 mA·cm–2). This work provides a method to develop multimetallic hydroxides for electrocatalysis and energy conversion.

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We explore the signatures of Majorana fermions in a nanowire based topological superconductor-quantum dot-topological superconductor hybrid device by charge transport measurements. At zero magnetic field, well-defined Coulomb diamonds and the Kondo effect are observed. Under the application of a finite, sufficiently strong magnetic field, a zero-bias conductance peak structure is observed. It is found that the zero-bias conductance peak is present in many consecutive Coulomb diamonds, irrespective of the even-odd parity of the quasi-particle occupation number in the quantum dot. In addition, we find that the zero-bias conductance peak is in most cases accompanied by two differential conductance peaks, forming a triple-peak structure, and the separation between the two side peaks in bias voltage shows oscillations closely correlated to the background Coulomb conductance oscillations of the device. The observed zero-bias conductance peak and the associated triple-peak structure are in line with Majorana fermion physics in such a hybrid topological system.

In this paper, a new type of memory motors, namely the dc-excited memory motor, is proposed and implemented. The concept of dc-excited memory is due to the nature that the magnetization level of permanent magnets (PMs) in the motor can be regulated by a temporary dc current pulse and be automatically memorized. Based on an outer-rotor doubly salient motor structure, the proposed dc-excited memory motor can offer effective and efficient online air-gap flux control. Hence, it possesses the advantages of mechanical robustness, high efficiency, and wide constant power operation region. Both simulation and experimentation are carried out to verify the validity of the proposed motor.

Developing cost-efficient hydrogen evolution reaction (HER) electrocatalysts for water splitting has long been a big challenge. Here, a hybrid of Fe doped CoSe 2 incorporated in nitrogen doped carbon (Fe-CoSe 2 @NC) was synthesized by selenization of Fe 3+ -etched metal organic frameworks (ZIF-67). As a result of the electronic structure engineering and morphology design, the Fe-CoSe 2 @NC hybrid showed an enhanced HER performance with a low overpotential of −143 mV for 10 mA cm −2 and a small Tafel slope of ∼40 mV dec −1 . It also exhibited good stability and a high Faradiac efficiency. The enhanced HER activity might be owing to the increased active surface area due to Fe 3+ ions etching. Moreover, the density functional theory (DFT) calculations indicate that the improved HER activity of Fe-CoSe 2 could be attributed to the favorable adsorption−desorption behavior and accelerated HER kinetics, which was induced by the doping of iron atoms into CoSe 2 . This work comes up with a valuable strategy in designing and improving advanced electrocatalysts.

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