야구 토토PHYSICS/BK21 Colloquium(09
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"토토 사이트 * PHYSICS/BK21 Colloquium *
“Investigations of the Effects of Defects
on the First Order Vortex Melting Transition
in YBa2Cu3O7-δ Single Crystals”
ØSpeaker : Prof. Lisa Paulius [Western Michigan University]
ØPlace : 토토 사이트 Seminar Room (Science Bldg, 3-201)
ØDate & Time : Mar. 13(Fri)토토 사이트4:00 ~ 5:00 pm
Abstract
The first order vortex melting transition is very sensitive to the presence of disorder and
can be supplanted by a second order phase transition in the토토 사이트presence토토 사이트of a sufficiently
high density of defects. We present the results토토 사이트of systematic토토 사이트studies on the effects of
defects on the first order vortex melting transition in YBa2Cu3O7-δ single crystals, with a
special focus on the upper and lower critical points. The experiments were토토 사이트performed
with electrical transport and ac specific heat토토 사이트measurements. The geometry and strength
of the defects varied,토토 사이트including토토 사이트naturally occurring twin boundaries as well as detwinned
single crystals토토 사이트irradiated with successive doses of electrons,토토 사이트protons, or heavy토토 사이트ions.
Twin boundaries yield planar defects,토토 사이트electron irradiation yielded weak point토토 사이트defects,
proton irradiation yielded strong point-like defects and토토 사이트heavy토토 사이트ion토토 사이트irradiation yielded
strong columnar defects. Our results토토 사이트indicate that the토토 사이트origins토토 사이트of the upper and lower
critical points of the first order melting transition arise from different mechanisms. The
position of the lower critical토토 사이트point is determined by the pinning strength of the defect,
whereas the upper critical point shifts in response to the geometrical correlation of the
defects.
Contact Person : Prof. Ki Bong Lee (054-279-2068, kibong@postech.ac.kr)토토 사이트토토 사이트"
“Investigations of the Effects of Defects
on the First Order Vortex Melting Transition
in YBa2Cu3O7-δ Single Crystals”
ØSpeaker : Prof. Lisa Paulius [Western Michigan University]
ØPlace : 토토 사이트 Seminar Room (Science Bldg, 3-201)
ØDate & Time : Mar. 13(Fri)토토 사이트4:00 ~ 5:00 pm
Abstract
The first order vortex melting transition is very sensitive to the presence of disorder and
can be supplanted by a second order phase transition in the토토 사이트presence토토 사이트of a sufficiently
high density of defects. We present the results토토 사이트of systematic토토 사이트studies on the effects of
defects on the first order vortex melting transition in YBa2Cu3O7-δ single crystals, with a
special focus on the upper and lower critical points. The experiments were토토 사이트performed
with electrical transport and ac specific heat토토 사이트measurements. The geometry and strength
of the defects varied,토토 사이트including토토 사이트naturally occurring twin boundaries as well as detwinned
single crystals토토 사이트irradiated with successive doses of electrons,토토 사이트protons, or heavy토토 사이트ions.
Twin boundaries yield planar defects,토토 사이트electron irradiation yielded weak point토토 사이트defects,
proton irradiation yielded strong point-like defects and토토 사이트heavy토토 사이트ion토토 사이트irradiation yielded
strong columnar defects. Our results토토 사이트indicate that the토토 사이트origins토토 사이트of the upper and lower
critical points of the first order melting transition arise from different mechanisms. The
position of the lower critical토토 사이트point is determined by the pinning strength of the defect,
whereas the upper critical point shifts in response to the geometrical correlation of the
defects.
Contact Person : Prof. Ki Bong Lee (054-279-2068, kibong@postech.ac.kr)토토 사이트토토 사이트"
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