Novel vortex distribution in the β-pyrochlore superconductor KOs2O6
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چکیده
By utilizing the micro-Hall probe array, we study the superconducting and the vortex states in a single crystal of KOs2O6 near the first-order transition at Tp ∼ 8 K, which is associated with a change in the rattling motion of K ions. We show that below the first-order transition, the lower critical field exhibits a distinct decrease, suggesting that the electron-phonon coupling is weakened below the transition. At high magnetic fields, the local magnetization shows an unexpectedly large jump at Tp with a sign change near the sample edges. Our results demonstrate a novel redistribution of vortices whose energy is reduced abruptly below the first-order transition at Tp.
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تاریخ انتشار 2008