Campbell penetration depth in low carrier density superconductor YPtBi
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Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.
For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.
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Abstract
Magnetic penetration depth, λm, was measured as a function of temperature and magnetic field in single crystals of low carrier density superconductor YPtBi by using a tunnel-diode oscillator technique. Measurements in zero DC magnetic field yield London penetration depth, λL(T), but in the applied field the signal includes the Campbell penetration depth, λC(T), which is the characteristic length of the attenuation of small excitation field, HAC, into the Abrikosov vortex lattice due to its elasticity. Whereas the magnetic field dependent λC exhibit λC∼Bp with p=1/2 in most of the conventional and unconventional superconductors, we found that p≈0.23≪1/2 in YPtBi due to rapid suppression of the pinning strength. From the measured λC(T,H), the critical current density is jc≈40A/cm2 at 75 mK. This is orders of magnitude lower than that of conventional superconductors of comparable Tc.