Baturina T I, Strunk C, Baklanov M R, Satta A
Institute of Semiconductor Physics, 630090, Novosibirsk, Russia.
Phys Rev Lett. 2007 Mar 23;98(12):127003. doi: 10.1103/PhysRevLett.98.127003. Epub 2007 Mar 21.
We investigate ultrathin superconducting TiN films, which are very close to the localization threshold. Perpendicular magnetic field drives the films from the superconducting to an insulating state, with very high resistance. Further increase of the magnetic field leads to an exponential decay of the resistance towards a finite value. In the limit of low temperatures, the saturation value can be very accurately extrapolated to the universal quantum resistance h/e2. Our analysis suggests that at high magnetic fields a new ground state, distinct from the normal metallic state occurring above the superconducting transition temperature, is formed. A comparison with other studies on different materials indicates that the quantum metallic phase following the magnetic-field-induced insulating phase is a generic property of systems close to the disorder-driven superconductor-insulator transition.
我们研究了非常接近局域化阈值的超薄超导氮化钛（TiN）薄膜。垂直磁场会将薄膜从超导态驱动到绝缘态，此时电阻非常高。进一步增加磁场会导致电阻朝着一个有限值呈指数衰减。在低温极限下，饱和值可以非常精确地外推到普适量子电阻h/e²。我们的分析表明，在高磁场下会形成一种新的基态，它不同于超导转变温度以上出现的正常金属态。与其他关于不同材料的研究进行比较表明，磁场诱导绝缘相之后的量子金属相是接近无序驱动的超导体-绝缘体转变的系统的一个普遍特性。
