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Symmetry plays a key role in classifying topological phases. Recent theory shows that in the presence of gauge fields, the algebraic structure of crystalline symmetries needs to be projectively represented, which brings extra chance for topological physics. Here, we report a concrete acoustic realization of mirror Chern insulators by exploiting the concept of projective symmetry. Specifically, we introduce a simple but universal recipe for constructing projective mirror symmetry, and conceive a minimal model for achieving the projective symmetry-enriched mirror Chern insulators. Based on our selective-excitation measurements, we demonstrate unambiguously the projective mirror eigenvalue-locked topological nature of the bulk states and associated chiral edge states. We extract the non-abelian Berry curvature and identify the mirror Chern number directly, providing experimental evidence for this exotic topological phase. All experimental results agree well with the theoretical predictions. Our findings give insights into topological systems equipped with gauge fields. A recurring theme in physics has been the discovery of distinctive phases of matter. Here, the authors propose a general recipe for constructing projective mirror symmetry and report an experimental realization of mirror Chern insulators in spinless systems. [ABSTRACT FROM AUTHOR]

Integrated phononics plays an important role in both fundamental physics and technology. Despite great efforts, it remains a challenge to break time-reversal symmetry to achieve topological phases and non-reciprocal devices. Piezomagnetic materials offer an intriguing opportunity as they break time-reversal symmetry intrinsically, without the need for an external magnetic field or an active driving field. Moreover, they are antiferromagnetic, and possibly compatible with superconducting components. Here, we develop a theoretical framework that combines linear elasticity with Maxwell's equations via piezoelectricity and/or piezomagnetism beyond the commonly adopted quasi-static approximation. Our theory predicts and numerically demonstrates phononic Chern insulators based on piezomagnetism. We further show that the topological phase and chiral edge states in this system can be controlled by the charge doping. Our results exploit a general duality relation between piezoelectric and piezomagnetic systems, which can potentially be generalized to other composite metamaterial systems. Understanding and controlling symmetry in nature is of paramount importance. In this work, the authors reveal an unexpected effect of the general duality relation between piezoelectricity and piezomagnetism on their symmetries, enabling novel phononic Chern insulators. [ABSTRACT FROM AUTHOR]

Microorganism invasion is still a severe threat for wound healing, which usually induces severe complications and cannot be eradicated completely. Thus, a biodegradable nanomaterial for guarding against bacteria-associated wound infection and accelerating wound healing is of vital importance. Here, black phosphorus nanosheets (BPs) were successfully decorated with cationic carbon dots (CDs) through an in situ growth strategy. The BPs@CDs exhibit photon-responsiveness and contact-responsiveness as an antibacterial agent, which shorten wound healing time. Moreover, the BPs@CDs show available photothermal and photodynamic therapy via exploring their photothermal properties and the ability of singlet-oxygen (1O2) production. Astonishingly, the BPs@CDs could possess antibacterial activity even without laser illumination due to an electrostatic attraction between bacteria and cationic CDs on the surface of BPs. This chemical therapy causes the antibacterial process to occur more accurately and for a faster 1O2 release to kill bacteria than in a normal process. Importantly, BPs@CDs display outstanding cytocompatibility and hemocompatibility. In vitro and in vivo investigations demonstrate that the BPs@CDs have enhanced antibacterial effect and can significantly accelerate skin tissue regeneration and wound closure. Given their antibacterial triple-combination therapy and excellent physicochemical properties, the broad application of BPs@CDs in bacteria-associated wound management is anticipated. [ABSTRACT FROM AUTHOR]

The properties of van der Waals (vdW) materials often vary dramatically with the atomic stacking order between layers, but this order can be difficult to control. Trilayer graphene (TLG) stacks in either a semimetallic ABA or a semiconducting ABC configuration with a gate-tunable band gap, but the latter has only been produced by exfoliation. Here we present a chemical vapor deposition approach to TLG growth that yields greatly enhanced fraction and size of ABC domains. The key insight is that substrate curvature can stabilize ABC domains. Controllable ABC yields ~59% were achieved by tailoring substrate curvature levels. ABC fractions remained high after transfer to device substrates, as confirmed by transport measurements revealing the expected tunable ABC band gap. Substrate topography engineering provides a path to large-scale synthesis of epitaxial ABC-TLG and other vdW materials. The semiconducting ABC configuration of trilayer graphene is more challenging to grow on large scales than its semimetallic ABA counterpart. Here, an approach to trilayer growth via chemical vapor deposition is presented that utilizes substrate curvature to yield enhanced fraction and size of ABC domains. [ABSTRACT FROM AUTHOR]

This paper describes the influence on the compressive and dissipative behavior of entangled metallic wire material (EMWM) samples provided by their size and mutual connectivity. The mechanical properties of EMWM specimens with different thicknesses are obtained from quasi-static compressive and cyclic loading. The behavior of the stress-strain curves, tangent modulus, and loss factor are strongly dependent on the thickness of the samples. The analysis from samples connected in different layouts shows that apart from the global thickness, size scale effects and contact interface also play important roles in controlling the behavior of EMWM systems. The importance of the sample size and its connectivity with adjacent different layers are defined by the unique microstructure and contact properties of the wires near the specimen boundary layer. The boundary layer produces different mechanical behaviors and a distinct structural configuration compared to the EMWM bulk solid. These peculiar characteristics are confirmed by microstructural and qualitative observations obtained from computed tomography scanning. The results and analysis presented in this work are relevant to designing EMWM material systems with adaptive performance under different loading and geometric constraints. [ABSTRACT FROM AUTHOR]