Low-temperature resistivity of underdoped cuprates

interest to note that the relative amplitude of the oscillations (about 10 ± 15% of the conductance) does not change for sample lengths between 1000 A and a few mm. For samples longer than 10mm the fluctuation magnitude decays strongly. It seems reasonable, therefore, to speculate that there is a typical coherence length, a few microns in size, which plays a role similar to LF in a normal metal. A small magnetic field can have two types of influence on the I ±V curves. Features which stem from exceeding a supercurrent are expected to be slightly shifted to smaller bias values because of the dependence of Ic onH. In addition, H introduces a phase change in each loop, altering any I ±V features associated with quantum interference. Hence our notion that the fluctuations stem from interference effects, while the I ±V discontinuities represent destruction of dc superconductivity in links is further supported by the dependence of the dV= dI ±V curves on the magnetic field as illustrated in Fig. 4. Note that a magnetic field of 300 Oe, while much smaller than Hc of the grains, is larger than the typical field scale for the conductance fluctuations (a few tens of Oe as seen in Fig. 3). Such a field is indeed expected to modify the interference pattern and give rise to a totally different fluctuation trace for both H ˆ 300 Oe and H ˆ y300 Oe.

Перевод пока недоступен