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Effect of Magnetic field on the Pseudogap Phenomena in High-Tc Cuprates

We theoretically investigate the effect of magnetic field on the pseudogap phenomena in High-Tc cuprates. The obtained results well explain the experimental results including their doping dependences. In our previous paper (J. Phys. Soc. Jpn. 68 (1999) 2999.), we have shown that the pseudogap phenomena observed in High-Tc cuprates are naturally understood as a precursor of the strong coupling superconductivity. On the other hand, there is an interpretation for the recent high field NMR measurements to be an evidence denying the pairing scenarios for the pseudogap. In this paper, we investigate the magnetic field dependence of NMR $1/T_{1}T$ on the basis of our formalism and show the interpretation to be inappropriate. The results indicate that the value of the characteristic magnetic field $B_{\rm ch}$ is remarkably large in case of the strong coupling superconductivity, especially near the pseudogap onset temperature $T^{*}$. Therefore, the magnetic field dependences can not be observed and $T^{*}$ does not vary when the strong pseudogap anomaly is observed. On the other hand, $B_{\rm ch}$ is small in the comparatively weak coupling case and $T^{*}$ varies when the weak pseudogap phenomena are observed. These results properly explain the high magnetic field NMR experiments continuously from under-doped to over-doped cuprates. Moreover, we discuss the transport phenomena in the pseudogap phase. The behaviors of the in-plane resistivity, the Hall coefficient and the c-axis resistivity in the pseudogap phase are naturally understood by considering the d-wave pseudogap.