Velocity renormalization of nodal quasiparticles in d-wave superconductors
Velocity renormalization of nodal quasiparticles in d-wave superconductors
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DOI：
10.1103/physrevb.87.054511
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发表时间：
2013-02
影响因子：
3.7
通讯作者：
Jing Wang
中科院分区：
文献类型：
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作者：
Jing Wang
由于d_{x^2 - y^2}$带隙对称性，在高T_c铜氧化物超导体的低能区出现了无带隙节状准粒子。我们研究了超导圆顶中这些准粒子的费米速度v_F$和能隙速度v_{\Delta}$在不同量子临界点附近的反常重整化。特别注意的行为的速度比，$v_{\Delta}/v_F$，因为它决定了一些可观察到的量。我们进行了重整化群分析，并表明，速度比可能消失，接近统一，或发散在不同的量子临界点。相应的超流密度和临界温度被抑制，略有增加，或显着提高。三种类型的静态无序，即随机质量，随机规范势，和随机化学势，对系统的稳定性的影响也得到了解决。一个类似的分析表明，随机质量和随机规范势都是无关的。这意味着这些速度比的固定点是稳定的，因此由它们引发的可观测效应是不变的。然而，随机化学势是边际的。结果，这些不动点被打破，从而触发量子相变的不稳定性。
Gapless nodal quasiparticles emerge at a low-energy regime of high-$T_c$ cuprate superconductors due to the $d_{x^2 - y^2}$ gap symmetry. We study the unusual renormalizations of the Fermi velocity $v_F$ and gap velocity $v_{\Delta}$ of these quasiparticles close to various quantum critical points in a superconducting dome. Special attention is paid to the behavior of the velocity ratio, $v_{\Delta}/v_F$, since it determines a number of observable quantities. We perform a renormalization-group analysis and show that the velocity ratio may vanish, approach unity, or diverge at different quantum critical points. The corresponding superfluid densities and critical temperatures are suppressed, slightly increased, or significantly enhanced. The effects of three types of static disorders, namely, random mass, random gauge potential, and random chemical potential, on the stability of the system are also addressed. An analogous analysis reveals that both random mass and random gauge potential are irrelevant. This implies that these fixed points of the velocity ratio are stable, and hence observable effects ignited by them are unchanged. However, the random chemical potential is marginal. As a result, these fixed points are broken, and thus, the instabilities of quantum phase transitions are triggered.