论文标题
冷全息超流体中的非变化正常密度
Non-vanishing normal density in cold holographic superfluids
论文作者
论文摘要
具有两个流体流动的流体动力模型很好地描述了表现出超丰富性的$ d+1 $维系统的低能量和有限温度激励，即正常流动和超流动流动。在量子临界点附近，系统中的热力学和运输有望由临界指数和远离量子临界点的无关变形的光谱控制。在这里，使用量规 - 重力二元性，我们以关键指数在流体动力衍生物膨胀中以一阶的一阶呈现热力学和电荷传输系数的低温依赖性。将特别注意具有新兴红外形式和LIFSHITZ对称性系统中正常流动的电荷密度的行为，并由LifShitz动力学指数$ z> 1 $进行参数。当$ 1 \ leq z <d+2 $时，我们恢复（$ z = 1 $），并扩展（$ z> 1 $）通过相对论有效的现场理论技术获得的先前结果。相反，当$ z> d+2 $时，我们表明正常的电荷密度在零温度下变为不变。扩展的附录将这些结果推广到违反高度标准的系统以及具有广义光子质量的系统。我们的结果阐明了全息文献中先前的工作，并与最近对库酸酯超导体的超氟密度的实验测量相关。
The low energy and finite temperature excitations of a $d+1$-dimensional system exhibiting superfluidity are well described by a hydrodynamic model with two fluid flows: a normal flow and a superfluid flow. In the vicinity of a quantum critical point, thermodynamics and transport in the system are expected to be controlled by the critical exponents and by the spectrum of irrelevant deformations away from the quantum critical point. Here, using gauge-gravity duality, we present the low temperature dependence of thermodynamic and charge transport coefficients at first order in the hydrodynamic derivative expansion in terms of the critical exponents. Special attention will be paid to the behavior of the charge density of the normal flow in systems with emergent infrared conformal and Lifshitz symmetries, parameterized by a Lifshitz dynamical exponent $z>1$. When $1\leq z<d+2$, we recover ($z=1$) and extend ($z>1$) previous results obtained by relativistic effective field theory techniques. Instead, when $z>d+2$, we show that the normal charge density becomes non-vanishing at zero temperature. An extended appendix generalizes these results to systems that violate hyperscaling as well as systems with generalized photon masses. Our results clarify previous work in the holographic literature and have relevance to recent experimental measurements of the superfluid density on cuprate superconductors.
