L'A' Cerquoni, S'M' Newlander, and J'D' Hettinger, - PowerPoint PPT Presentation
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L'A' Cerquoni, S'M' Newlander, and J'D' Hettinger,
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... the peaks that are associated with a vortex dimensional crossover are observed. ... You need defects to observe the dimensional crossover. ... – PowerPoint PPT presentation
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Title: L'A' Cerquoni, S'M' Newlander, and J'D' Hettinger,
1
Evidence for Reduced Vortex Line Tension in Ion
Irradiated 2H-NbSe2
- L.A. Cerquoni, S.M. Newlander, and J.D.
Hettinger, - Physics Section, Rowan University, Glassboro NJ
- S. Bhattacharya and M.J. Higgins
- NEC Research Institute, Princeton NJ
- Dean Miller, Ken Gray, Eric E. Fullerton
- Materials Science Division, Argonne National
Laboratory, Argonne, IL - present address IBM Almaden
- This work was partially supported by the
Petroleum Research Fund and the Research
Corporation
2
Background
- The resistance of any superconductor
decreases sharply towards zero at the critical
temperature.
- Zero resistance property makes superconducting
Normal
Superconducting
3
In a Magnetic Field
- Vortices form a lattice structure
- Magnetic field suppresses superconducting
transition.
4
Additional Dissipation Due to Vortex Motion in
Superconductors
5
Layered Superconductors
- Preventing vortex motion-pinning vorticies
- 2 D superconductors- disk-like vorticies
- 3 D superconductors- rod-like vortices
- Anisotropic superconductors- have a finite
interaction between layers resulting in a finite
line tension
6
NbSi Rotated in a Magnetic Field
- As the field is rotated parallel to the Nb/Si
layers another peak is observed
B
q
7
Simple Explanation
2D
3D
B?
8
NbSe2
- NbSe2 is a single crystal
- Two peaks are formed that resemble the peaks
observed in NbSi.
9
NbSe2 nF 5x109 defects/cm2
- If defects are added to the sample by ion
irradiation the peaks that are associated with a
vortex dimensional crossover are observed.
10
NbSe2 nF 9.6x1010 defects/cm2
- If more defects are added the peaks disappear.
11
Recap
- The new peak observed when magnetic field is
nearly aligned with the layers is indicates that
the vortices move as two-dimensional entities at
angles close to 90. - You need defects to observe the dimensional
crossover. - Is the peak effect observed by others in the
NbSe2 a result of a meandering vortex line?
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