Charged vortices in high-temperature superconductors probed by NMR

Abstract

We report a first experimental evidence that a vortex in the high temperature superconductors (HTSC) traps a finite electric charge from the high resolution measurements of the nuclear quadrupole frequencies. In slightly overdoped YBa2Cu3O7 the vortex is negatively charged by trapping electrons, while in underdoped YBa2Cu4O8 it is positively charged by expelling electrons. The sign of the trapped charge is opposite to the sign predicted by the conventional BCS theory. Moreover, in both materials, the deviation of the magnitude of the charge from the theory is also significant. These unexpected features can be attributed to the novel electronic structure of the vortex in HTSC.

Temperature dependence of the Cu(2) NQR line width in YBa2Cu3O7−y

“…There are grounds to believe that the broadening at T < T c depends on the doping level of the sample. For instance, the Cu(2) NQR line width measured in 3 for an overdoped Y1237 sample virtually did not change in the temperature range 300-10 K, although the line width (about 290 kHz) was not too small; i.e., the sample studied in that work was not defectless.…”

Nuclear resonance shift in the vortex lattice inYBa2Cu3O7Lipavský1, Koláček2, Morawetz3 et al. 2002Phys. Rev. B14030View full textAdd to dashboardCite

“…13 The 63 Cu atom in the CuO 2 plane subjected to the magnetic field, B c, with a number of holes, N , has NMR frequencies ν 1 = γ Cu B and ν 2,3 = γ Cu B ∓ (C + AN ) .…”

“…3 in Ref. 13. The frequenciesν 3,2 , used by KNM in formula (2) are positions of the maxima of F 2,3 (ν).…”

The Concept of Correlated Density and Its Application

“…Kumagai et al 29 have measured the quadrupole resonance lines in the high-T c material YBCO. The polarization of the Cu atoms leads to a coupling of spins with the electrical field gradient and to a splitting of the quadrupole resonance…”