YBa₂Cu₄O₈の高圧NQR

抄録

The temperature dependence of the ⁶³Cu nuclear spin-lattice relaxation rate (T₁T)^-1 , spin-spin relaxation rate T_2G^-1 and frequency spectra at the Cu(2) planar site in the normal state of YBa₂Cu₄O₈ have been measured under high pressure by the nuclear quadrupole resonance(NQR) technique. The pseudo spin gap temperature slightly decreased with increasing pressure. It seems that the pressure effects are resembled with carrier doping effects in the increase of superconducting transition temperature T_c and NQR frequency ν_Q(2) and decrease of pseudo spin gap temperature. If the increase of ν_Q(2) under pressure was caused by introducing carrier into Cu(2) planar site, the change of pseudo spin gap temperature is generally originated in carrier concentration at Cu(2) site.