Thermodynamic stability of small-world oscillator networks: A case study of proteins

We study vibrational thermodynamic stability of small-world oscillator networks, by relating the average mean-square displacement $S$ of oscillators to the eigenvalue spectrum of the Laplacian matrix of networks. We show that the cross-links suppress $S$ effectively and there exist two phases on the small-world networks: 1) an unstable phase: when $p\ll1/N$, $S\sim N$; 2) a stable phase: when $p\gg1/N$, $S\sim p^{-1}$, \emph{i.e.}, $S/N\sim E_{cr}^{-1}$. Here, $p$ is the parameter of small-world, $N$ is the number of oscillators, and $E_{cr}=pN$ is the number of cross-links. The results are exemplified by various real protein structures that follow the same scaling behavior $S/N\sim E_{cr}^{-1}$ of the stable phase. We also show that it is the "small-world" property that plays the key role in the thermodynamic stability and is responsible for the universal scaling $S/N\sim E_{cr}^{-1}$, regardless of the model details.Comment: 7 pages, 5 figures, accepted by Physical Review

Non-Reciprocal Geometric Wave Diode by Engineering Asymmetric Shapes of Nonlinear Materials

Unidirectional nonreciprocal transport is at the heart of many fundamental problems and applications in both science and technology. Here we study the novel design of wave diode devices by engineering asymmetric shapes of nonlinear materials to realize the function of non-reciprocal wave propagations. We first show analytical results revealing that both nonlinearity and asymmetry are necessary to induce such non-reciprocal (asymmetric) wave propagations. Detailed numerical simulations are further performed for a more realistic geometric wave diode model with typical asymmetric shape, where good non-reciprocal wave diode effect is demonstrated. Finally, we discuss the scalability of geometric wave diodes. The results open a flexible way for designing wave diodes efficiently simply through shape engineering of nonlinear materials, which may find broad implications in controlling energy, mass and information transports.Comment: 4 figure

Intertwined Orders in Holography: Pair and Charge Density Waves

Building on [1], we examine a holographic model in which a U(1) symmetry and translational invariance are broken spontaneously at the same time. The symmetry breaking is realized through the St\"{u}ckelberg mechanism, and leads to a scalar condensate and a charge density which are spatially modulated and exhibit unidirectional stripe order. Depending on the choice of parameters, the oscillations of the scalar condensate can average out to zero, with a frequency which is half of that of the charge density. In this case the system realizes some of the key features of pair density wave order. The model also admits a phase with co-existing superconducting and charge density wave orders, in which the scalar condensate has a uniform component. In our construction the various orders are intertwined with each other and have a common origin. The fully backreacted geometry is computed numerically, including for the case in which the theory contains axions. The latter can be added to explicitly break translational symmetry and mimic lattice-type effects.Comment: 37 pages, 17 figure

Quantum Zeno effect as a topological phase transition in full counting statistics and spin noise spectroscopy

When the interaction of a quantum system with a detector is changing from weak to strong coupling limits, the system experiences a transition from the regime with quantum mechanical coherent oscillations to the regime with a frozen dynamics. In addition to this quantum Zeno transition, we show that the full counting statistics of detector signal events experiences a topological phase transition at the boundary between two phases at intermediate coupling of a quantum system to the detector. We demonstrate that this transition belongs to the class of topological phase transitions that can be classified by elements of the braid group. We predict that this transition can be explored experimentally by means of the optical spin noise spectroscopy.Comment: 5 pages, 2 figure

Fabrication of nanostructured surfaces with well-defined chemistry using particle lithography

Natural self-assembly processes provide nanofabrication capabilities for designing surfaces with nanoscale control of surface chemistry and relative orientation of the nanomaterials on the surfaces. Particle lithography was used to produce periodic arrays of protein nanostructures. Monodisperse mesoparticles can be applied to rapidly prepare millions of uniform protein nanostructures on flat surfaces using the conventional benchtop chemistry steps of mixing, centrifuging, evaporation and drying. Nanopatterns of bovine serum albumin and staphylococcal protein A were produced with particle lithography. The immobilized proteins remain attached to the surface and form nanopatterns over micron areas corresponding to the thickness of a single layer of proteins. The morphology and diameter of the protein nanostructures are tunable by selecting the ratios of protein-to-particle and the diameters of spheres. Organosilane nanopatterns were fabricated using particle lithography combined with vapor deposition to regulate surface chemistry. Colloidal masks produced by particle lithography enable to control and direct the placement of nanoscopic residues of water for hydrosilation. Different geometries of silane nanostructures depend on the length of drying for particle masks. Organosilanes form covalent bonds with the surface through hydrolysis, which provide an excellent platform for further steps of chemical modification. The head groups of organosilane nanopatterns can be designed to generate spatial selectivity for electroless deposition of iron oxide and selective adsorption of gold nanoparticles. New imaging strategies using atomic force microscopy (AFM) were developed for mapping magnetic domains and elastic compliance at size regimes below 100 nm. The AFM-based imaging mode is referred to as magnetic sample modulation (MSM). The AFM tip serves as a force and motion sensor for mapping the vibrational response of magnetic nanomaterials. The information acquired from MSM images includes the distribution of individual magnetic domains as well as spectra of the characteristic resonance frequencies of the vibrating nanomaterials. Indirect magnetic modulation (IMM) based on indirect oscillation of soft nonmagnetic cantilevers was used to investigate elastic response of organosilane nanostructures. With the use of IMM, dynamic parameters of the driving frequencies and amplitude of the tip motion can be optimized to sensitively map the elastic response of samples