Calculation of Penetration Depth and T_c in κ-(ET)_2Cu(NCS)_2 under Pressure(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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The pressure dependence of the inverse square of the magnetic penetration depth λ^<-2> in κ-(ET)_2Cu (NCS)_2 was measured by Larkin et al. [Phys. Rev B 64 (2001) 144514]. According to the paper, λ^<-2> behaves differently under low pressure and under high pressure. Under low pressure, the development of λ^<-2> just below T = T_c is rapid compared to the case under high pressure. Moreover, T_c in κ-(ET)_2Cu(NCS)_2 increases under c-axis pressure up to 1 kbar and decreases under higher pressure, while T_c decreases monotonically under the hydrostatic pressure, or under the uniaxial pressure parallel to other axes. In order to explain these behaviors, we calculate Tc and λ^<-2> for κ-(ET)_2Cu(NCS)_2 under pressure. In the calculation we mainly use an effective dimer Hubbard model. In conclusion, the behavior of λ^<-2> results from three effects : the variation of the bandwidth of quasiparticles, the change of the Fermi surfaces, and the effect of vertex correction This is a different mechanism from that of λ^<-2> in cuprates which we observe when the doping varies. Moreover, we explain the increase in T_c under the c-axis pressure up to 1 kbar and the decrease in T_c over 1 kbar from our calculation With the increase in the c-axis pressure, two competitive effects with respect to T_c appear. One is the approach of the Fermi surface to the antiferromagnetic Brillouin zone boundary, and the other is the suppression of the electron correlation Under the low c-axis pressure, T_c increases since the former effect is dominant. On the other hand, T_c decreases since the latter effect is dominant under the high c-axis pressure.
社団法人日本物理学会の論文
2004-12-15

Calculation of Penetration Depth and T_c in κ-(ET)_2Cu(NCS)_2 under Pressure(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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