Researchers have studied the normal-superconducting phase transition in thehigh-$T_c$ cuprates in a magnetic field (the vortex-glass or Bose-glasstransition) and in zero field. Often, transport measurements in "zero field"are taken in the Earth's ambient field or in the remnant field of a magnet. Weshow that fields as small as the Earth's field will alter the shape of thecurrent vs. voltage curves and will result in inaccurate values for thecritical temperature $T_c$ and the critical exponents $\nu$ and $z$, and caneven destroy the phase transition. This indicates that without proper screeningof the magnetic field it is impossible to determine the true zero-fieldcritical parameters, making correct scaling and other data analysis impossible.We also show, theoretically and experimentally, that the self-field generatedby the current flowing in the sample has no effect on the current vs. voltageisotherms.
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机译：研究人员研究了在磁场（涡玻璃或玻色玻璃跃迁）和零场中高T_c $铜酸盐中的正常超导相变。通常，在“零场”中的传输测量是在地球的环境场或磁体的剩余场中进行的。我们表明，与地球场一样小的场将改变电流与电压曲线的形状，并导致临界温度$ T_c $和临界指数$ \ nu $和$ z $的值不准确，甚至破坏相变。这表明如果没有适当地屏蔽磁场，就不可能确定真实的零磁场临界参数，从而不可能进行正确的缩放和其他数据分析。我们还从理论和实验上证明了由样品中流动的电流产生的自磁场对电流与电压等温线没有影响。
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