Quantum shell effects in compressed mesoscopic system.

The article demonstrates the nontrivial manifestation of quantum shell effects in a compressed mesoscopic system. It is shown that there are two spatial scales in the distribution of degenerate electrons in a spherical well. The first scale is the Fermi length $\sim h/p_{\rm F}$. By quantum shell effect, the authors mean the existence of the new spatial scale, which is order of the system size and much larger than the first scale. The theoretical analysis for the large amount of free electrons ($N \lesssim 10^9$) in an infinite spherical well demonstrates what causes the appearance of the spatial nonuniformity and gives analytical expression for the electron distribution function. These results are confirmed by a numerical summation of exact solutions for the electron wave functions in an infinite potential well. It is shown that an analogous effect for the spatial distribution of electrons exists in a compressed hydrogen gas bubble of submicron size ($<0.1 \mu m$). The numerical simulation of the electron distribution was carried out by the DFT (Density Functional Theory) method. The consequence of this effect is the nontrivial dynamics of the compressible cold gas bubble. This system can be realized in the thermonuclear experiments. The limiting factors of the analyzed effect are considered: symmetry of system, electron temperature, and curvature of system boundary.