二维量子逾渗的动力学问题

Dynamical properties of a three-dimensional diluted Heisenberg model

We study the magnetic excitation spectrum in three-dimensional diluted ferromagnetic nearest-neighbor systems down to the percolation threshold. The disorder effects resulting from the dilution are handled accurately within self-consistent local random phase approximation approach. The calculations are performed using relatively large systems containing typically 20 000 localized spins, a systematic average over many configurations of disorder is performed. We analyze in details the change in the magnon spectrum and magnon density of states as we increase the dilution. The zone of stability of…

稀释磁体中的逾渗量子相变

Percolation quantum phase transitions in diluted magnets

我们表明，几何临界性和量子涨落的相互作用导致一个新的普适类的渗流量子相变在稀释磁体。所有涉及动力学关联的临界指数都不同于经典的渗流值，但在二维中它们仍然可以精确地确定。我们开发了一个完整的标度理论，这种转变，我们把它与最近的实验在La $_{2}$铜$_{1-p}$（锌，镁）$_{p}$ O $_{4}$。我们的结果也是相关的无序相互作用玻色子系统。

Complex critical exponents for percolation transitions in Josephson-junction arrays, antiferromagnets, and interacting bosons

We show that the critical behavior of quantum systems undergoing a percolation transition is dramatically affected by their topological Berry phase $2πρ$. For irrational $ρ$, we demonstrate that the low-energy excitations of diluted Josephson-junctions arrays, quantum antiferromagnets, and interacting bosons are spinless fermions with fractal spectrum. As a result, critical properties not captured by the usual Ginzburg-Landau-Wilson description of phase transitions emerge, such as complex critical exponents, log-periodic oscillations and dynamically broken scale-invariance.

Quantum percolation and magnetic nano-dropletstates in electronically phase-separated manganite nanowires

One-dimensional (1D) confinement has been revealed to effectively tune the properties of materials in homogeneous states. The 1D physics can be further enriched by electronic inhomogeneity, which unfortunately remains largely unknown. Here we demonstrate the ultra-high sensitivity to magnetic fluctuations and the tunability of phase stability in the electronic transport properties of self-assembled electronically phase-separated manganite nanowires with extreme aspect ratio. The onset of magnetic nano-droplet state, a precursor to the ferromagnetic metallic state, is unambiguously revealed, wh…