论文标题
在薄膜中的量子超导金属过渡附近的奇怪金属状态
Strange metal state near quantum superconductor-metal transition in thin films
论文作者
论文摘要
我们在二维金属中发展了量子$ t = 0 $ t = 0 $相位转换（q-SMT）的理论，并具有冷冻的空间波动$δλ（r）$的库珀吸引力常数。当波动的强度$δλ（r）$超过一定的临界大小，由于自发形成超导相位的局部液滴，Q-SMT的平均场状场景破裂。这些液滴的密度随着平均吸引力常数$λ$的增加而成倍增长。液滴的顺序参数之间的相互作用是由于正常金属的接近效应以及距离$ \ propto 1/r^β$的比例，$ 2 <β\ le 3 $。我们通过真实空间强度重新归一化组（RG）来解释这种相互作用。在Q-SMT附近，RG流量正式为kosterlitz- thouless rg的双重等同。相应的固定点线描述了金属的Griffith阶段，具有大型超导岛的分形簇。集群中的典型岛屿数量随着$n_Δ\ sim 1/δ$的增长，其中$ 0 <δ\ ll 1 $是到临界点的距离。超导侧用RG轨迹进入强耦合区域描述。靠近SC侧的过渡点，$ 0 <-Δ\ ll 1 $，RG轨迹具有极值作为RG参数$ |δ|δ|^{1/2} \ ln（1/Tτ）$的函数。它导致宽温度范围，即物理特性几乎不依赖$ t $。该观察结果可能与对\ emph {奇怪的金属}状态的理解有关，经常在Q-SMT附近观察到。
We develop a theory of quantum $T = 0$ phase transition (q-SMT) between metal and superconducting ground states in a two-dimensional metal with frozen-in spatial fluctuations $δλ(r)$ of the Cooper attraction constant. When strength of fluctuations $δλ(r)$ exceeds some critical magnitude, usual mean-field-like scenario of the q-SMT breaks down due to spontaneous formation of local droplets of superconducting phase. The density of these droplets grows exponentially with the increase of average attraction constant $λ$. Interaction between the droplet's order parameters is due to proximity effect via normal metal and scales with distance $\propto 1/r^β$ , with $2 < β\le 3$. We account for this interaction by means of a real-space strong-disorder renormalization group (RG). Near the q-SMT the RG flow is, formally, a dual equivalent of the Kosterlitz-Thouless RG. The corresponding line of fixed points describes a Griffiths phase of a metal with large fractal clusters of superconducting islands. Typical number of islands in a cluster grows as $N_δ\sim 1/δ$, where $0 < δ\ll 1 $ is the distance to the critical point. Superconducting side is described by a runaway of RG trajectories into the strong-coupling region. Close to the transition point on the SC side, $0<-δ\ll 1$, RG trajectories possess an extremum as function of the RG parameter $|δ|^{1/2} \ln(1/Tτ)$. It results in a wide temperature range where physical properties are nearly $T$-independent. This observation may be relevant to the understanding of a \emph{strange metal} state frequently observed near q-SMT.
