Quantization and confinement effects in superconducting nanostructures |
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Institution: | 1. Department of Physical Engineering, Kim Chaek University of Technology, Pyongyang, Democratic People’s Republic of Korea;2. Institute of Nano Science and Physical Engineering, Kim Chaek University of Technology, Pyongyang, Democratic People’s Republic of Korea |
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Abstract: | The confinement of the flux lines by a lattice of submicron holes (‘antidots’) has been studied in nanostructured superconducting Pb/Ge multilayers. By introducing regular arrays of sufficiently large antidots, multi-quanta vortex lattices have been stabilized. Sharp cusp-like magnetization (M) anomalies, appearing at matching fieldsHm=mφ0/Sin superconducting films with the antidot lattices having a unit cell areaS, are successfully explained. These anomalies are, analogues of the well-knownM(H) cusp atHc1, but for the onset of multi-quanta (m+1)φ0-vortices penetration at each subsequent matching fieldHm. It is shown that theM(H) curve between the matching fieldsHm<H<Hm+1follows a simpleM∝ln(H−Hm) dependence. These experimental observations have revealed an unusual expansion of validity of the London limit in superconductors with lattices of relatively large antidots. The successful high quality fit of theM(H,T) curves convincingly demonstrates that a new type of the critical stateB=const (‘single-terrace critical state’) can be realized in superconductors with the antidot lattices. |
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