Doiron-Leyraud N, Walker I R, Taillefer L, Steiner M J, Julian S R, Lonzarich G G
Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK.
Nature. 2003 Oct 9;425(6958):595-9. doi: 10.1038/nature01968.
Fermi-liquid theory (the standard model of metals) has been challenged by the discovery of anomalous properties in an increasingly large number of metals. The anomalies often occur near a quantum critical point--a continuous phase transition in the limit of absolute zero, typically between magnetically ordered and paramagnetic phases. Although not understood in detail, unusual behaviour in the vicinity of such quantum critical points was anticipated nearly three decades ago by theories going beyond the standard model. Here we report electrical resistivity measurements of the 3d metal MnSi, indicating an unexpected breakdown of the Fermi-liquid model--not in a narrow crossover region close to a quantum critical point where it is normally expected to fail, but over a wide region of the phase diagram near a first-order magnetic transition. In this regime, corrections to the Fermi-liquid model are expected to be small. The range in pressure, temperature and applied magnetic field over which we observe an anomalous temperature dependence of the electrical resistivity in MnSi is not consistent with the crossover behaviour widely seen in quantum critical systems. This may suggest the emergence of a well defined but enigmatic quantum phase of matter.
费米液体理论（金属的标准模型）已受到越来越多金属中反常特性发现的挑战。这些反常现象通常出现在量子临界点附近——在绝对零度极限下的连续相变，典型情况是在磁有序相和顺磁相之间。尽管尚未完全理解其细节，但近三十年前超越标准模型的理论就已预测到此类量子临界点附近会出现异常行为。在此，我们报告了对3d金属MnSi的电阻率测量结果，表明费米液体模型出现了意外的失效——并非在通常预期其失效的靠近量子临界点的狭窄交叉区域，而是在靠近一级磁转变的相图的广泛区域。在这个区域，预计对费米液体模型的修正很小。我们观察到MnSi中电阻率的反常温度依赖性所涉及的压力、温度和外加磁场范围，与量子临界系统中广泛观察到的交叉行为不一致。这可能暗示着一种定义明确但神秘的量子物质相的出现。
