Strong Field Quenching of the Quasiparticle Effective Mass in Heavy Fermion Compound YbCo2Zn20
Strong Field Quenching of the Quasiparticle Effective Mass in Heavy Fermion Compound YbCo2Zn20
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DOI：
10.1143/jpsj.79.083601
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发表时间：
2010-08-01
影响因子：
1.7
通讯作者：
Onuki, Yoshichika
中科院分区：
文献类型：
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作者：
Ohya, Masahiro;Matsushita, Masaki;Onuki, Yoshichika
我们发现重费米子化合物YbCo_2 Zn_（20）在低于特征温度T_（chi_max）= 0.32K时，在H_m处出现类似变磁的反常现象，其值等于或等于5 kOe，此时交流磁化率出现一个宽峰，这表明该化合物是一个具有很低近藤温度的电子态。有趣的是，在电子比热C/T的磁场依赖性中，在95 mK下，在4.0和7.5 kOe处观察到类似变磁的行为。m.cm/K-2H = 0 kOe时电阻率rho = rho（0）+ AT（2）中，电子比热系数γ的极大值接近或等于8000 mJ/（K-2.mol）和A = 160 μ，这很可能是由于非常低的Kondo温度。然而，发现根A值从0 kOe时的根A = 12.6（μ Ω·cm/K-2）（1/2）到150 kOe时的根A = 0.145（μ Ω·cm/K-2）（1/2）显著降低。因此，我们认为相应的回旋有效质量m（c）*，这是由de Haas-van Alphen（dHvA）振幅的温度依赖性确定的，也随着磁场的增加而减小，实际上并不大，在117 kOe处从2到9 m（0）。根据根A和m（c）* 与场的关系，我们估算了0 kOe处的回旋有效质量为100- 500 m（0），这是目前已知的最大回旋质量。
We found a metamagnetic like anomaly at H-m similar or equal to 5 kOe in a heavy fermion compound YbCo2Zn20 below the characteristic temperature T-chi max = 0.32K where the ac-susceptibility shows a broad peak, suggesting that an electronic state with a very low Kondo temperature is realized. Interestingly, the metamagnetic like behavior was observed as two peaks at 4.0 and 7.5 kOe at 95 mK in the magnetic field dependence of the electronic specific heat C/T. The extremely large values of the electronic specific heat coefficient gamma similar or equal to 8000 mJ/(K-2.mol) and A = 160 mu m.cm/K-2 in the electrical resistivity rho = rho(0) + AT(2) at H = 0 kOe are most likely due to the very low Kondo temperature. The root A value was, however, found to be strongly reduced from root A = 12.6 (mu Omega.cm/K-2)(1/2) at 0 kOe to 0.145 (mu Omega.cm/K-2)(1/2) at 150 kOe. Therefore, we considered that the corresponding cyclotron effective mass m(c)*, which was determined from the temperature dependence of the de Haas-van Alphen (dHvA) amplitude, is also reduced with increasing magnetic field and is in fact not large, ranging from 2 to 9m(0) at 117 kOe. From the field dependence of root A and m(c)*, we estimated the cyclotron effective mass at 0 kOe to be 100-500m(0), revealing the largest cyclotron mass as far as we know.