Quantum bicriticality in the heavy-fermion metamagnet YbAgGe.
Quantum bicriticality in the heavy-fermion metamagnet YbAgGe.
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DOI：
10.1103/physrevlett.111.116401
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发表时间：
2013-06
影响因子：
8.6
通讯作者：
Y. Tokiwa;Markus Garst;P. Gegenwart;S. Bud’ko;P. Canfield
中科院分区：
文献类型：
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作者：
Y. Tokiwa;Markus Garst;P. Gegenwart;S. Bud’ko;P. Canfield
双临界点，两个不同的对称破缺相同时变得不稳定，是典型的自旋翻转变磁。有趣的是，重费米子化合物YbAgGe在μH(BCP)≈4.5 T的磁场下也具有低温T(BCP)≈0.3 K的双临界点（BCP）。在其附近，YbAgGe表现出异常行为，我们将其归因于一个量子双临界点的影响，该量子双临界点在参数空间上很接近，但可以通过将T（BCP）进一步调至零来达到。通过对磁热效应的高分辨率测量，我们证明了磁颗粒<s:1>尼森参数ΓH确实会根据量子临界性的要求改变符号和发散。此外，ΓH仅在低场侧H > H（BCP）处表现出典型的标度行为，表明其相对于临界场具有明显的不对称性。我们推测T（BCP）的小值与YbAgGe的Kondo晶格的几何挫折有关。
Bicritical points, at which two distinct symmetry-broken phases become simultaneously unstable, are typical for spin-flop metamagnetism. Interestingly, the heavy-fermion compound YbAgGe also possesses such a bicritical point (BCP) with a low temperature T(BCP)≈0.3 K at a magnetic field of μH(BCP)≈4.5 T. In its vicinity, YbAgGe exhibits anomalous behavior that we attribute to the influence of a quantum bicritical point that is close in parameter space yet can be reached by tuning T(BCP) further to zero. Using high-resolution measurements of the magnetocaloric effect, we demonstrate that the magnetic Grüneisen parameter ΓH indeed both changes sign and diverges as required for quantum criticality. Moreover, ΓH displays a characteristic scaling behavior but only on the low-field side H≲H(BCP), indicating a pronounced asymmetry with respect to the critical field. We speculate that the small value of T(BCP) is related to the geometric frustration of the Kondo lattice of YbAgGe.