Electronic cooling of a submicron-sized metallic beam

亚微米尺寸软铁磁薄圆柱中磁涡旋的磁中子散射

Magnetic neutron scattering by magnetic vortices in thin submicron-sized soft ferromagnetic cylinders

本研究针对亚微米软铁磁薄圆柱的磁涡旋，推导了小角中子散射截面的闭式表达式，推进了相关数据分析，还提出提取涡旋结构细节的方法以解决磁涡旋位移模式的长期问题。

A Current Induced Transition in atomic-sized contacts of metallic Alloys

We have measured conductance histograms of atomic point contacts made from the noble-transition metal alloys CuNi, AgPd, and AuPt for a concentration ratio of 1:1. For all alloys these histograms at low bias voltage (below 300 mV) resemble those of the noble metals whereas at high bias (above 300 mV) they resemble those of the transition metals. We interpret this effect as a change in the composition of the point contact with bias voltage. We discuss possible explanations in terms of electromigration and differential diffusion induced by current heating.

Metallic bonds become molecular-like in atomic-sized devices

Covalent molecules are characterized by directed bonds, which provide stability-of-form to the molecules relative atomic positions. In contrast, bulk metals are characterized by delocalized bonds, where a large number of resonance structures ensure their high stability. However, reduced to atomic dimensions, metallic arrangements become increasingly vulnerable to disruptive entropic fluctuations. Using the smallest possible device, namely, a single atom held between two atomically sharp probes, force to rupture single-atom bridges was measured with pico-level resolution, using gold and silver.…

Strain sensing with sub-micron sized Al-AlOx-Al tunnel junctions

We demonstrate a local strain sensing method for nanostructures based on metallic Al tunnel junctions with AlOx barriers. The junctions were fabricated on top of a thin silicon nitride membrane, which was actuated with an AFM tip attached to a stiff cantilever. A large relative change in the tunneling resistance in response to the applied strain (gauge factor) was observed, up to a value 37. This facilitates local static strain variation measurements down to ~10^{-7}.

Role of electronic structure in photoassisted transport through atomic-sized contacts

We study theoretically quantum transport through laser-irradiated metallic atomic-sized contacts. The radiation field is treated classically, assuming its effect to be the generation of an ac voltage over the contact. We derive an expression for the dc current and compute the linear conductance in one-atom thick contacts as a function of the ac frequency, concentrating on the role played by electronic structure. In particular, we present results for three materials (Al, Pt, and Au) with very different electronic structures. It is shown that, depending on the frequency and the metal, the radiat…

Complete stabilization and improvement of the characteristics of tunnel junctions by thermal annealing

We have observed that submicron sized Al--AlO{$_x$}--Al tunnel junctions can be stabilized completely by annealing them in vacuum at temperatures between $350^{\circ}$C and $450^{\circ}$C. In addition, low temperature characterization of the samples after the annealing treatment showed a marked improvement of the tunneling characteristics due to disappearance of unwanted resonances in the current. Charging energy, tunneling resistance, barrier thickness and height all increase after the treatment. The superconducting gap is not affected, but supercurrent is reduced in accordance with the incre…