Magnetically Robust Non-Fermi Liquid Behavior in Heavy Fermion Systems with f2-Configuration: Competition between Crystalline-Electric-Field and Kondo–Yosida Singlets

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In f2-based heavy fermion systems with a crystalline-electric-field (CEF) singlet ground state, the non-Fermi liquid (NFL) arises around the quantum critical point (QCP) due to the competition between the CEF singlet and the Kondo–Yosida singlet states. In such a case, the characteristic temperature $T_{\text{F}}^{*}$ at which the entropy starts to decrease toward zero is suppressed by the effect of the competition, compared to both energy scales characterizing each singlet state, the lower Kondo temperature ($T_{\text{K2}}$) and the CEF splitting ($\Delta$). We show that in the case of tetragonal symmetry $T_{\text{F}}^{*}$ is not affected by the magnetic field up to $H_{z}^{*}$ which is determined by the distance from the QCP or characteristic energy scales of each singlet states, not by $T_{\text{F}}^{*}$ itself. As a result, in the vicinity of QCP, there are parameter regions where the NFL is robust against the magnetic field, at an observable temperature range $T > T_{\text{F}}^{*}$, up to $H_{z}^{*}$ which is far larger than $T_{\text{F}}^{*}$ and less than $\min(T_{\text{K2}},\Delta)$. Our result suggests that such an anomalous NFL behavior can arise also in systems with other CEF symmetry, which might provide us with the basis to understand the anomalous behaviors of UBe13.
2010-10-15