Question

Materials displaying this phenomenon expel their magnetic field in the Meissner effect. For 10 points each:
[10e] Name this phenomenon which a 2023 preprint falsely claimed LK-99 was able to display at room temperature.
ANSWER: superconductivity [or superconductors]
[10m] The characteristic coherence length was introduced in this macroscopic theory of superconductivity. The central equations of this theory are used to compute the complex order parameter.
ANSWER: Ginzburg–Landau theory [or Landau–Ginzburg theory; accept Ginzburg–Landau equations; reject “Landau theory”]
[10h] Whether a superconductor is Type I or II depends on the value of the ratio of coherence length to penetration depth, since it determines the sign of this quantity. For positive values of this quantity, boundaries are unfavorable, giving rise to Type I superconductors.
ANSWER: surface energy [accept sigma sub ns; prompt on energy; prompt on sigma]
<Physics>

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Summary

2025 ACF Nationals04/19/2025Y2211.82100%18%0%

Data

Toronto AArizona State100010
Chicago AColumbia A1010020
Columbia BWaterloo B100010
OttawaHarvard100010
Illinois ANYU100010
IndianaMIT1010020
Illinois BIowa State100010
Johns HopkinsStanford1010020
LSEMaryland100010
UC Berkeley ANorth Carolina B1010020
NorthwesternGeorgia State100010
Ohio StateVirginia Tech100010
RutgersRIT100010
TexasGeorgia Tech100010
Toronto BMichigan100010
UC Berkeley BUCF100010
VirginiaPenn State100010
FloridaWUSTL A100010
WUSTL BBritish Columbia100010
VanderbiltWaterloo A100010
Winona StateMinnesota100010
Chicago BToronto C100010