0000000001290981
AUTHOR
M. Zgirski
Resistive state of quasi-one-dimensional superconductors: Fluctuations vs. sample inhomogeneity
The shape of experimentally observed R(T) transition of thin superconducting wires is analyzed. Broadening of the transition in quasi-1-dimensional superconducting channels is typically associated with phase slip mechanism provided by thermal or quantum fluctuations. It is shown that consideration of inevitable geometrical inhomogeneity and finite dimensions of real samples studied in experiments is of primary importance for interpretation of results. The analysis is based on experimental fact that for many superconducting materials the critical temperature is a function of characteristic dimension of a low-dimensional system: film thickness or wire cross section
Electron-phonon heat transport and electronic thermal conductivity in heavily doped silicon-on-insulator film
Electron–phonon interaction and electronic thermal conductivity have been investigated in heavily doped silicon at subKelvin temperatures. The heat flow between electron and phonon systems is found to be proportional to T6. Utilization of a superconductor–semiconductor–superconductor thermometer enables a precise measurement of electron and substrate temperatures. The electronic thermal conductivity is consistent with the Wiedemann–Franz law. Peer reviewed
Phase Slip Phenomena in Ultra-Thin Superconducting Wires
We present results on phase-slip phenomena in a superconducting wire which can be considered as quasi-one dimensional (1D) if its characteristic transverse dimension \( \sqrt \sigma\) (√ being the cross section) is smaller than the coherence length Λ(T). The shape of the bottom part of the resistive transition R(T) of a 1D superconducting strip is described by the model of phase slips activation. If the wire is infinitely long, then there is always a finite probability that a small part of the sample is instantly driven normal.
Size-dependent enhancement of superconductivity in Al and Sn nanowires: shape-resonance effect
A shape-dependent superconducting resonance can be expected when an energy level associated with the transverse motion in a wire passes through the Fermi surface. We show that the recently observed width-dependent increase of ${T}_{c}$ in Al and Sn nanowires is a consequence of this shape-resonance effect.
Ion beam shaping and downsizing of nanostructures
We report a new approach for progressive and well-controlled downsizing of nanostructures below the 10 nm scale. Low energetic ion beam (Ar+) is used for gentle surface erosion, progressively shrinking the dimensions with ~ 1 nm accuracy. The method enables shaping of nanostructure geometry and polishing the surface. The process is clean room / high vacuum compatible being suitable for various applications. Apart from technological advantages, the method enables study of various size phenomena on the same sample between sessions of ion beam treatment.
Quantum fluctuations in ultranarrow superconducting aluminum nanowires
Progressive reduction of the effective diameter of a nanowire is applied to trace evolution of the shape of the superconducting transition $R(T)$ in quasi-one-dimensional aluminum structures. In nanowires with effective diameter $\ensuremath{\leqslant}15\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ the $R(T)$ dependences are much wider than predicted by the model of thermally activated phase slips. The effect can be explained by quantum fluctuations of the order parameter. Negative magnetoresistance is observed in the thinnest samples. Experimental results are in reasonable agreement with existing theoretical models. The effect should have a universal validity, indicating a breakdown of the zero-…
Experimental limits of the observation of thermally activated phase-slip mechanism in superconducting nanowires
The shape of experimentally observed $R(T)$ transition of thin superconducting wires is analyzed. From theoretical point of view, broadening of the transition in quasi-one-dimensional superconducting channels is typically associated with phase-slip mechanism. It is shown that such interpretation can be misleading if to consider geometrical inhomogeneity and finite dimensions of real samples studied in experiments. The analysis is based on experimental fact that for many superconducting materials the critical temperature depends on the characteristic dimension of a sample: film thickness or wire cross section.
Size-dependent enhancement of superconductivity in nanowires
A shape-dependent superconducting resonance can be expected when an energy level associated with the transverse motion in a wire passes through the Fermi surface. We show that the recently observed width-dependent increase of $T_c$ in ${\rm Al}$ and ${\rm Sn}$ nanowires is a consequence of this shape resonance effect.
Size Dependent Breakdown of Superconductivity in Ultranarrow Nanowires
Below a certain temperature Tc (typically cryogenic), some materials lose their electric resistance R entering a superconducting state. Folowing the general trend toward a large scale integration of a greater number of electronic components, it is desirable to use superconducting elements in order to minimize heat dissipation. It is expected that the basic property of a superconductor, i.e. dissipationless electric current, will be preserved at reduced scales required by modern nanoelectronics. Unfortunately, there are indications that for a certain critical size limit of the order of 10 nm, below which a "superconducting" wire is no longer a superconductor in a sense that it acquires a fin…