arXiv subjects

Man Shen

Publications and source records attributed to Man Shen.

6 recordsLinked to original sources

arXiv2026

Mechanical bistability and hysteresis in graphene-CNT hybrid systems: from atomistic simulations to macroscale structural responses

Hybrid systems composed of graphene (Gr) and carbon nanotubes (CNTs), such as films and aerogels, have attracted broad attention for applications in electronics, mechanics, energy, and environmental science. Since the microstructures of Gr-CNT hybrids strongly affect their properties, it is essential to establish mechanical principles that govern these structures. In this study, we investigated the structural stability and mechanical behavior of Gr-CNT hybrid systems by combining molecular dynamics (MD) simulations and nanoindentation experiments. MD simulations of stacked Gr-CNT structures, in which two Gr layers confine CNTs between them, identified the energetically stable configurations and their governing parameters, i.e., intertube spacing, CNT diameter, and wall number. Specifically, under certain conditions, the structures exhibit mechanical bistability with two stable configurations: adhesion and separation of the Gr layers, arising from the competition between interlayer van der Waals attraction and elastic deformation of Gr and CNTs. Simulated loading--unloading curves display hysteresis and energy dissipation related to the stable configurations. In addition, reduced graphene oxide (rGO)-CNT hybrid films were experimentally fabricated as macroscopic assemblies of the unit structures modeled in the simulations. Atomic force microscopy-based nanoindentation measurements on the rGO-CNT films exhibit clear hysteresis and higher dissipation energy compared with pure rGO, in good agreement with the simulation results. These results provide valuable insights into Gr-CNT hybrid systems and offer guidance for designing microstructures with enhanced properties for advanced applications.

cond-mat.mtrl-sci↗

arXiv2026

Dynamical generation of stable optical-microwave squeezing in structured reservoirs

Two-mode squeezed states as paradigmatic entangled resources have broad applications in quantum information processing. Here, we study the generation of stable optical-microwave squeezing in structured environments within a hybrid electro-optomechanical system, where a mechanical oscillator is simultaneously coupled to an optical cavity mode and a microwave mode of an LC resonator. Specifically, an effective Hamiltonian that captures the optical-microwave squeezing interaction is constructed by combining strongly modulated driving fields applied to both photonic modes with a mechanical parametric amplifier. Based on this effective model, the dynamical evolution of two-mode squeezing in structured environments is analyzed. It is remarkably shown that the non-Markovian noise can substantially enhance the squeezing level in comparison to the Markovian case, and that two-mode squeezing can persist even in the absence of external driving fields under non-Markovian conditions, thereby mitigating the detrimental effects of anti-squeezing. Furthermore, the persistence of the two-mode squeezed state is enhanced when the environmental spectral densities of the microwave and optical modes are identical. Our work provides a theoretical framework for generating and persisting two-mode squeezing in structured environments.

quant-ph↗

arXiv2025

Efficient defect healing of single-walled cabron nanotubes through $ \mathrm{C}_{2}\mathrm{H}_{2} $-assisted multiple-cycle treatment with air exposure

Defects in single-walled carbon nanotubes (SWCNTs) degrade their mechanical,electrical, and thermal properties, limiting their potential applications. To realize the diverse applications of SWCNTs, it is essential to enhance their crystallinity through effective defect healing. However, traditional thermal treatments typically require temperatures above 1800{\deg}C, which can alter the nanotube structure. Previously, defect healing of SWCNTs was achieved at a relatively low temperature of 1100{\deg}C, using C$_{2}$H$_{2}$ assistance, but the efficiency was limited. In this study, we developed a C$_{2}$H$_{2}$-assisted multiple-cycle process at an even lower temperature of 1000{\deg}C combined with air exposure, achieving highly efficient defect healing while preserving the nanotube structure. The combination of multiple-cycle treatment and air exposure between cycles was found to promote defect activation, suppress the formation of amorphous carbon, and enhance the effectiveness of defect healing. Additionally, we successfully healed commercially available bulk-scale SWCNTs (super-growth SWCNTs), noting that their healing behavior differed from lab-grown SWCNTs with smaller diameters synthesized from nanodiamond. The efficient and structure-preserved healing process developed in this study broadens the potential applications of high-quality SWCNTs, including flexible electronics, high-performance composites, and energy storage devices.

cond-mat.mtrl-sci↗

arXiv2014

The Coexistence and Decoupling of Bulk and Edge States in Disordered Two-dimensional Topological Insulators

We investigate the scattering and localization properties of edge and bulk states in a disordered two-dimensional topological insulator when they coexist at the same fermi energy. Due to edge-bulk backscattering (which is not prohibited \emph{a priori} by topology or symmetry), Anderson disorder makes the edge and bulk states localized indistinguishably. Two methods are proposed to effectively decouple them and to restore robust transport. The first kind of decouple is from long range disorder, since edge and bulk states are well separated in $k$ space. The second one is from an edge gating, owing to the edge nature of edge states in real space. The latter can be used to electrically tune a system between an Anderson insulator and a topologically robust conductor, i.e., a realization of a topological transistor.

cond-mat.mes-hall↗

arXiv2014

Effects of Rashba spin-orbit coupling and a magnetic field on a polygonal quantum ring

Using standard quantum network method, we analytically investigate the effect of Rashba spin-orbit coupling (RSOC) and a magnetic field on the spin transport properties of a polygonal quantum ring. Using Landauer-Buttiker formula, we have found that the polarization direction and phase of transmitted electrons can be controlled by both the magnetic field and RSOC. A device to generate a spin-polarized conductance in a polygon with an arbitrary number of sides is discussed. This device would permit precise control of spin and selectively provide spin filtering for either spin up or spin down simply by interchanging the source and drain.

cond-mat.mes-hall↗

arXiv2014

Valley polarization in graphene-silicene-graphene heterojunction

Considering the difference of energy bands in graphene and silicene, we put forward a new model of the graphene-silicene-graphene (GSG) heterojunction. In the GSG, we study the valley polarization properties in a zigzag nanoribbon in the presence of an external electric field. We find the energy range associated with the bulk gap of silicene has a valley polarization more than 95%. Under the protection of the topological edge states of the silicene, the valley polarization remains even the small non-magnetic disorder is introduced. These results have certain practical significance in applications for future valley valve.

cond-mat.mes-hall↗