Nuclear spin relaxation rate near the disorder-driven quantum critical point in Weyl fermion systems
Nuclear spin relaxation rate near the disorder-driven quantum critical point in Weyl fermion systems
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DOI：
10.1103/physrevb.101.155103
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发表时间：
2019-12
影响因子：
3.7
通讯作者：
Tomoki Hirosawa;H. Maebashi;M. Ogata
中科院分区：
文献类型：
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作者：
Tomoki Hirosawa;H. Maebashi;M. Ogata
无序，如Weyl半金属中的杂质和位错，驱动了量子临界点(QCP)，其中Weyl点处的态密度获得了非零值。在QCP附近，物理量的渐近低能奇点由临界指数n和z控制。核自旋-晶格驰豫速率源于Weyl费米子系统中核自旋与长程轨道流之间的超精细耦合，它显示出有趣的临界行为。基于杂质的自洽Born近似，我们研究了无序Weyl Sm中轨道流引起的核自旋晶格驰豫速率$1/{T}{1}$。我们发现在QCp处的${({T}_{1}T)}^{\ensuremath{-}1}\ensuremath{\sim}{E}^{2/z}$，其中$E$是相对于Weyl点的温度$T$和化学势的最大值。自洽的$T$-矩阵近似也证实了${(T}_{1}T)}^{\EnsureMath{-}1}$的标度行为，其中$\EnsureMath{\Mu}(T)$的显著的温度依赖性可能起到重要作用。我们希望这些研究结果能对探索Weyl材料中无序驱动的量子临界性起到推动作用。
Disorder such as impurities and dislocations in Weyl semimetals drives a quantum critical point (QCP) where the density of states at the Weyl point gains a nonzero value. Near the QCP, the asymptotic low-energy singularities of physical quantities are controlled by the critical exponents $\ensuremath{\nu}$ and $z$. The nuclear spin-lattice relaxation rate, which originates from the hyperfine coupling between a nuclear spin and long-range orbital currents in Weyl fermion systems, shows intriguing critical behavior. Based on the self-consistent Born approximation for impurities, we study the nuclear spin-lattice relaxation rate $1/{T}_{1}$ due to the orbital currents in disordered Weyl SMs. We find that ${({T}_{1}T)}^{\ensuremath{-}1}\ensuremath{\sim}{E}^{2/z}$ at the QCP where $E$ is the maximum of temperature $T$ and chemical potential $\ensuremath{\mu}(T)$ relative to the Weyl point. This scaling behavior of ${({T}_{1}T)}^{\ensuremath{-}1}$ is also confirmed by the self-consistent $T$-matrix approximation, where a remarkable temperature dependence of $\ensuremath{\mu}(T)$ could play an important role. We hope these results of ${({T}_{1}T)}^{\ensuremath{-}1}$ will serve as an impetus for exploration of the disorder-driven quantum criticality in Weyl materials.