Creep of beta-tin single crystals at subkelvin temperatures

Abstract

The creep of β-Sn single crystals oriented for slip in the (100)〈010〉 system is investigated in the temperature range 0.45–4.2 K. A transient creep, decaying in time by a logarithmic law, is registered both above and below 1 K. The temperature dependence of the coefficient of logarithmic creep is studied in detail, and the existence of two qualitatively different regions of its behavior is established: in the interval 4.2–1.2 K the coefficient increases linearly with decreasing temperature, while below 1 K the creep acquires an athermal character and the coefficient remains constant. It is shown that the regularities observed in the experiment are in accord with the idea that the kinetics of creep in pure β-Sn is governed by the motion of dislocations in the Peierls potential relief by a mechanism of nucleation of kink pairs on the dislocation lines. This process entails the overcoming of a small effective potential barrier of the order of 0.001 eV: in the temperature region T<1 K the nucleation of kink pairs occurs by a quantum tunneling effect, and the creep is of a purely quantum character; at higher temperatures the leading role is played by thermal fluctuations, and the deformation kinetics corresponds to the classical ideas of thermally activated creep. Empirical estimates are obtained for the density of mobile dislocations and the work hardening coefficient.

Carbon Nanotubes Encapsulating Superconducting Single-Crystalline Tin Nanowires

“…Additional information for the high degree of graphitization of the CNTs comes from Raman measurements (see Supporting Information). Comparing the present results with previous ones where tin nanowires (whiskers) were produced without the protecting CNTs 10,12 shows that the nanowires here are less straight and do not grow with a low-index crystal direction exactly along the nanowire axis. This difference can be understood since for noncovered nanowires the surface energy and facet formation play (during growth) a crucial role and will force the wire to have low energy facets along its long sides.…”

“…The data show a clear diamagnetic behavior below the bulk superconducting transition temperature for tin T c ) 3.72 K (indicated by the arrow). 10,12 The magnetization drops rapidly below the bulk T c , but a small tail in the magnetization remains at temperatures as high as 4.0 K. As shown below, the small increase of the T c onset is due to the thinnest nanowires in which the confinement and surface-to-volume ratio becomes large enough to influence the vibrational and electronic properties. The same has been reported in the literature 13 for tin nanowires of 20 nm diameter.…”

“…Without this paramagnetic background, the powder would still be diamagnetic at higher fields. This means that the onset of the superconducting critical field is higher than 0.4 T, which is more than 1 order of magnitude higher than the bulk thermodynamical critical field H c Bulk ) 0.021 T at 2 K. 12 Measurements above T c show that the apparent paramagnetic background is in fact the sum of a temperature-dependent paramagnetic signal, probably due to a few magnetic impurities, superimposed to a temperature-independent diamagnetic contribution. A simple removal of the background is shown in Figure 4b (black circles) where we see that the onset of critical field is of the order of 0.6 T. This increase in the critical field is a direct result of the reduced diameter of the nanowires.…”

Large critical magnetic field and tunneling anomaly behavior of superconducting carbon-coated Sn nanorods and nanoparticles

“…11 Another possible origin for the unchanged superconducting transition temperature is that this is an effect of increased surface area, which may enhance surface electron-phonon scattering effect and compensate the size effect of reducing the superconducting transition temperature. 32 This increase in the critical field is a direct result of the reduced size of nanorods. 3͑a͒.…”

Creep in solid 4He at temperatures below 1 K

“…It is also possible that the carriers of plastic deformation may overcome a potential barrier by quantum tunnelling or that there is a combination of thermally activated and quantum mechanical mechanisms for creep. Quantum motion of dislocations and quantum plasticity effects have been repeatedly discussed in studies of the mechanical properties of metallic crystals at temperatures on the order of and below 1 K. [22][23][24] …”