J. Phys. Soc. Jpn. 70 (2001) pp. 2054-2060 |Next Article| |Table of Contents|
|Full Text PDF (293K)| |Buy This Article|
Local Enhancement of Spin Susceptibility around a Nonmagnetic Impurity in the Normal State of High-Tc Cuprate Superconductors
Institute of Physics, University of Tsukuba, Ibaraki 305-8571
(Received April 13, 2001)
We investigate local characters of spin susceptibility around a nonmagnetic impurity in the normal state of high-Tc cuprate superconductors. In a model two-dimensional system with strong antiferromagnetic (AF) spin fluctuations and with an extended impurity potential which is finite not only at the impurity site but also around it, we find that the AF susceptibility and the uniform one are strongly enhanced around the impurity. In particular, the uniform susceptibility which is almost temperature-independent in the clean system remarkably increases with decreasing temperature. We also show that the local enhancement of the susceptibility is due to (1) an increase of the local density of states at the Fermi level near the impurity site, and (2) a mode-mode coupling effect which is caused by the impurity potential. Our results can explain the recent Knight shift measurements in YBa2(Cu1-xZnx)3O6+y and YBa2(Cu1-xLix)3O6+y showing a Curie-Weiss temperature dependence of the uniform susceptibility at (around) the impurities, and also agree with the recent experiments on the nuclear spin-lattice relaxation rate in Zn-doped YBa2Cu3O6+y and YBa2Cu4O8 which observed anomalous enhancement of the low-energy AF spin fluctuations.
©2001 The Physical Society of Japan
KEYWORDS:high-Tc-superconductor, spin susceptibility, nonmagnetic impurity effect, antiferromagnetic spin fluctuations
- M.-H. Julien, T. Fehér, M. Horvatić, C. Berthier, O. N. Bakharev, P. Ségansan, G. Collin and J.-F. Marucco:
Phys. Rev. Lett. 84 (2000) 3422[APS].
- Y. Itoh, T. Machi, M. Koshizuka: Advances in Superconductivity XII (Springer Verlag, Tokyo, 2000) p. 284.
- Y. Itoh, T. Machi, N. Watanabe, S. Adachi and N. Koshizuka: to be published in Physica C.
- P. Mendels, J. Bobroff, G. Collin, H. Alloul, M. Gabay, J. F. Marucco, N. Blanchard and B. Grenier: Eur. Phys. Lett. 46 (1999) 678.
- A. V. Mahajan, H. Alloul, G. Collin and J. F. Marucco:
Phys. Rev. Lett. 72 (1994) 3100[APS]; Eur. Phys. J. B 13 (2000) 457.
- J. Bobroff, W. A. MacFarlane, H. Alloul, P. Mendels, N. Blanchard, G. Collin and J.-F. Marucco:
Phys. Rev. Lett. 83 (1999) 4381[APS].
- D. Poilblanc, D. J. Scalapino and W. Hanke:
Phys. Rev. Lett. 72 (1994) 884[APS].
- S. Fujimoto:
- R. Kilian, S. Krivenko, G. Khaliullin and P. Fulde:
Phys. Rev. B 59 (1999) 14432[APS].
- N. Bulut:
Phys. Rev. B 61 (2000) 9051[APS].
- T. Xiang and J. M. Wheatley:
Phys. Rev. B 51 (1995) 11721[APS].
- H. Namba, Y. Onishi, H. Ikeda and K. Miyake: unpublished.
- Y. Kitaoka, K. Ishida and K. Asayama:
J. Phys. Soc. Jpn. 63 (1994) 2052[JPSJ].
- We briefly mention that “the first order perturbation” means retaining terms up to O(U) in a series of RPA-diagrams. In eq. (eq.3.1), χ0 itself includes the effect of U within HF approximation.
- Comparing Fig. fig:4(b) with Fig. fig:5(b), we find that, at some sites, e.g., at (0,0), the effect of LDOS is not enough to reproduce the enhancement of the AF susceptibility. At these sites, spatial variation of χ0 is also crucial as in the case of the uniform susceptibility.