Quantum-Mechanically Induced Asymmetry in the Phase Diagrams of Spin-Glass Systems

The spin-1/2 quantum Heisenberg model is studied in all spatial dimensions d by renormalization-group theory. Strongly asymmetric phase diagrams in temperature and antiferromagnetic bond probability p are obtained in dimensions d \geq 3. The asymmetry at high temperatures approaching the pure ferromagnetic and antiferromagnetic systems disappears as d is increased. However, the asymmetry at low but finite temperatures remains in all dimensions, with the antiferromagnetic phase receding to the ferromagnetic phase. A finite-temperature second-order phase boundary directly between the ferromagnetic and antiferromagnetic phases occurs in d \geq 6, resulting in a new multicritical point at its meeting with the boundaries to the paramagnetic phase. In d=3,4,5, a paramagnetic phase reaching zero temperature intervenes asymmetrically between the ferromagnetic and reentrant antiferromagnetic phases. There is no spin-glass phase in any dimension.Comment: Added discussion of second-order transitions between ordered phases, driven by quenched disorder. 4 pages, 1 figure, 3 tables. Published versio

Infinitely Robust Order and Local Order-Parameter Tulips in Apollonian Networks with Quenched Disorder

For a variety of quenched random spin systems on an Apollonian network, including ferromagnetic and antiferromagnetic bond percolation and the Ising spin glass, we find the persistence of ordered phases up to infinite temperature over the entire range of disorder. We develop a renormalization-group technique that yields highly detailed information, including the exact distributions of local magnetizations and local spin-glass order parameters, which turn out to exhibit, as function of temperature, complex and distinctive tulip patterns.Comment: 5 pages, 4 figures; updated to reflect minor changes in published versio

Frustrated Further-Neighbor Antiferromagnetic and Electron-Hopping Interactions in the d=3 tJ Model: Finite-Temperature Global Phase Diagrams from Renormalization-Group Theory

The renormalization-group theory of the d=3 tJ model is extended to further-neighbor antiferromagnetic or electron-hopping interactions, including the ranges of frustration. The global phase diagram of each model is calculated for the entire ranges of temperatures, electron densities, and further/first-neighbor interaction strength ratios. In addition to the \tau_{tJ} phase seen in earlier studies of the nearest-neighbor d=3 tJ model, the \tau_{Hb} phase seen before in the d=3 Hubbard model appears both near and away from half-filling. These distinct \tau phases potentially correspond to different (BEC-like and BCS-like) superconducting phases.Comment: Improved figures, added discussions, added references. Published version. 12 pages, 5 figures, 6 table

Infinitely Robust Order and Local Order-Parameter Tulips in Apollonian Networks with Quenched Disorder

For a variety of quenched random spin systems on an Apollonian network, including ferromagnetic and antiferromagnetic bond percolation and the Ising spin glass, we find the persistence of ordered phases up to infinite temperature over the entire range of disorder. We develop a renormalization-group technique that yields highly detailed information, including the exact distributions of local magnetizations and local spin-glass order parameters, which turn out to exhibit, as function of temperature, complex and distinctive tulip patterns

Dynamics of evaporative colloidal patterning

Drying suspensions often leave behind complex patterns of particulates, as might be seen in the coffee stains on a table. Here we consider the dynamics of periodic band or uniform solid film formation on a vertical plate suspended partially in a drying colloidal solution. Direct observations allow us to visualize the dynamics of the band and film deposition, and the transition in between when the colloidal concentration is varied. A minimal theory of the liquid meniscus motion along the plate reveals the dynamics of the banding and its transition to the filming as a function of the ratio of deposition and evaporation rates. We also provide a complementary multiphase model of colloids dissolved in the liquid, which couples the inhomogeneous evaporation at the evolving meniscus to the fluid and particulate flows and the transition from a dilute suspension to a porous plug. This allows us to determine the concentration dependence of the bandwidth and the deposition rate. Together, our findings allow for the control of drying-induced patterning as a function of the colloidal concentration and evaporation rate.Comment: 11 pages, 7 figures, 2 table

Dynamic, viscoelasticity-driven shape change of elastomer bilayers

Thin bilayers made of elastic sheets with different strain recoveries can be used for dynamic shape morphing through ambient stimuli, such as temperature, mass diffusion, and light. As a fundamentally different approach to designing temporal shape change, constituent polymer molecular features (rather than external fields) are leveraged, specifically the viscoelasticity of gelatin bilayers, to achieve dynamic three-dimensional (3D) curls and helical twists. After stretching and releasing, the acquired 3D shape recovers its original flat shape on a timescale originating from the polymer viscoelasticity. The bilayer time-dependent curvature can be accurately predicted from hyperelastic and viscoelastic functions using finite element analysis (FEA). FEA reveals the nonlinear shape dynamics in space and time in quantitative agreement with experiments. The findings present a new frontier in dynamic biomimetic shape-morphing by exploiting intrinsic material properties in contrast with state-of-the-art methods relying on external field variations, moving one step closer to acquiring autonomous shape-shifting capabilities of biological systems.Comment: For SI, see https://drive.google.com/file/d/1MH0kURA_OiOaePDQC06Eua1aG3kkEBV4/view?usp=sharin

Diffusio-phoretic fast swelling of chemically responsive hydrogels

Acid-induced release of stored ions from polyacrylic acid hydrogels (with a free surface fully permeable to the ion and acid flux) was observed to increase the gel osmotic pressure that leads to rapid, temporary swelling faster than the characteristic solvent absorption rate of the gel. Here we develop a continuum poroelastic theory that quantitatively explains the experiments by introducing a "gel diffusio-phoresis" mechanism: Steric repulsion between the gel polymers and released ions can induce a diffusio-osmotic solvent intake counteracted by the diffusio-phoretic expansion of the gel network. For applications ranging from drug delivery to soft robotics, engineering the gel diffusio-phoresis may enable stimuli-responsive hydrogels with amplified strain rates and power output