Quantum tricritical points in NbFe2
Quantum tricritical points in NbFe2
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DOI：
10.1038/nphys4242
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发表时间：
2018-01-01
期刊：
影响因子：
19.6
通讯作者：
Grosche, F. Malte
中科院分区：
文献类型：
--
作者：
Friedemann, Sven;Duncan, Will J.;Grosche, F. Malte
量子临界点（QCP）出现时，二级相变被抑制到零温度。在金属中，这种QCP的量子涨落可以产生新的相，包括非常规的超导性。虽然反铁磁QCP已经被相当详细地研究，但铁磁（FM）QCP更难获得。在几乎所有的金属中，FM QCP通过改变到一阶跃迁或通过介入自旋密度波（SDW）相来避免。在这里，我们研究第二种情况下，NbFe 2的原型。我们证明，相图可以使用一个两阶参数理论，其中假定的FMQCP是埋在SDW相。我们建立了量子三临界点（QTCPs）的存在下，在均匀和有限波矢磁化率发散。我们的模型的普遍性质表明，这种QTCP自然产生的SDW和FM顺序之间的相互作用，并存在于一般附近的这种类型的埋FMQCP。我们的研究结果促进NbFe 2作为QTCP的第一个例子，这已被提出作为一个关键的概念，在一系列的窄带金属，包括突出的重费米子化合物YbRh2Si2。
Quantum critical points (QCPs) emerge when a second-order phase transition is suppressed to zero temperature. In metals the quantum fluctuations at such a QCP can give rise to new phases, including unconventional superconductivity. Whereas antiferromagnetic QCPs have been studied in considerable detail, ferromagnetic (FM) QCPs are much harder to access. In almost all metals FM QCPs are avoided through either a change to first-order transitions or through an intervening spin-density-wave (SDW) phase. Here, we study the prototype of the second case, NbFe2. We demonstrate that the phase diagram can be modelled using a two-order-parameter theory in which the putative FMQCP is buried within a SDW phase. We establish the presence of quantum tricritical points (QTCPs) at which both the uniform and finite wavevector susceptibility diverge. The universal nature of our model suggests that such QTCPs arise naturally from the interplay between SDW and FM order and exist generically near a buried FMQCP of this type. Our results promote NbFe2 as the first example of a QTCP, which has been proposed as a key concept in a range of narrow-band metals, including the prominent heavy-fermion compound YbRh2Si2.