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arXiv 1506.06012cond-mat.dis-nn
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Dyson分级长程量子自旋玻璃的实空间重整化

Dyson Hierarchical Long-Ranged Quantum Spin-Glass via real-space renormalization

Cecile Monthus

摘要:

我们考虑Dyson分级版本的量子自旋玻璃与随机高斯耦合的幂律衰减方差$\overline{J^2(r)} \propto r^{-2σ}$和一个均匀的横向场$h$。通过实空间重正化研究了基态,以表征作为控制参数$h$的函数的玻璃-顺磁零温量子相变。在spingglass相$h<h_c$,典型的重整化耦合增长的长度尺度$L$的幂律$J_L^{typ}(h) \propto Υ(h) L^θ$与经典液滴指数$θ=1-σ$,其中的刚度模量消失在临界$Υ(h) \propto (h_c-h)^μ $,而典型的重整化横向场指数衰减$ h^{typ}_L(h) \propto e^{- \frac{L}ξ}$的相关长度发散在过渡$ξ\propto (h_c-h)^{-ν}$。在临界点$h=h_c$,典型的重整化耦合$J_L^{typ}(h_c) $和典型的重整化横场$ h^{typ}_L(h_c)$表现出相同的幂律行为$L^{-z}$,动力学指数为有限的$z$ . RG规则数值上应用到链包含$L=2^{12}=4096 $自旋,以测量这些临界指数的区域$1/2<σ<1$中的$σ$的各种值。

英文摘要:

We consider the Dyson hierarchical version of the quantum Spin-Glass with random Gaussian couplings characterized by the power-law decaying variance $\overline{J^2(r)} \propto r^{-2σ}$ and a uniform transverse field $h$. The ground state is studied via real-space renormalization to characterize the spinglass-paramagnetic zero temperature quantum phase transition as a function of the control parameter $h$. In the spinglass phase $h<h_c$, the typical renormalized coupling grows with the length scale $L$ as the power-law $J_L^{typ}(h) \propto Υ(h) L^θ$ with the classical droplet exponent $θ=1-σ$, where the stiffness modulus vanishes at criticality $Υ(h) \propto (h_c-h)^μ $, whereas the typical renormalized transverse field decays exponentially $ h^{typ}_L(h) \propto e^{- \frac{L}ξ}$ where the correlation length diverges at the transition $ξ\propto (h_c-h)^{-ν}$. At the critical point $h=h_c$, the typical renormalized coupling $J_L^{typ}(h_c) $ and the typical renormalized transverse field $ h^{typ}_L(h_c)$ display the same power-law behavior $L^{-z}$ with a finite dynamical exponent $z$. The RG rules are applied numerically to chains containing $L=2^{12}=4096 $ spins in order to measure these critical exponents for various values of $σ$ in the region $1/2<σ<1$.

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