Magnetic field induced finite size effect in type-II superconductors

• Veröffentlicht in: Физика низких температур
• Datum: 2006
• ISSN: 0132-6414
• 1. Verfasser: Schneider, T.
• Format: Artikel
• Sprache: Englisch
• Veröffentlicht: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2006
• Schlagworte: Spin Models
• Online Zugang: https://nasplib.isofts.kiev.ua/handle/123456789/120201
• Назва журналу: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Zitieren: Magnetic field induced finite size effect in type-II
 superconductors / T. Schneider // Физика низких температур. — 2006. — Т. 32, № 4-5. — С. 521–527. — Бібліогр.: 62 назв. — англ.

We explore the occurrence of a magnetic field induced finite size effect on the specific heat and
 correlation lengths of anisotropic type-II superconductors near the zero field transition temperature
 Tc. Since near the zero field transition thermal fluctuations are expected to dominate and with
 increasing field strength these fluctuations become one dimensional, whereupon the effect of fluctuations
 increases, it appears unavoidable to account for thermal fluctuations. Invoking the scaling
 theory of critical phenomena it is shown that the specific heat data of nearly optimally doped
 YBa₂Cu₃O₇₋δ are inconsistent with the traditional mean-field and lowest Landau level predictions
 of a continuous superconductor to normal state transition along an upper critical field
 Hс₂(T). On the contrary, we observe agreement with a magnetic field induced finite size effect,
 whereupon even the correlation length longitudinal to the applied field H cannot grow beyond the
 limiting magnetic length LH ∝ 0/H. It arises because with increasing magnetic field the density
 of vortex lines becomes greater, but this cannot continue indefinitely. LH is then roughly set
 on the proximity of vortex lines by the overlapping of their cores. Thus, the shift and the rounding
 of the specific heat peak in an applied field is traced back to a magnetic field induced finite size effect
 in the correlation length longitudinal to the applied field.