Review of borophene and its potential applications

Since two-dimensional boron sheet (borophene) synthesized on Ag substrates in 2015, research on borophene has grown fast in the fields of condensed matter physics, chemistry, material science, and nanotechnology. Due to the unique physical and chemical properties, borophene has various potential applications. In this review, we summarize the progress on borophene with a particular emphasis on the recent advances. First, we introduce the phases of borophene by experimental synthesis and theoretical predictions. Then, the physical and chemical properties, such as mechanical, thermal, electronic, optical and superconducting properties are summarized. We also discuss in detail the utilization of the borophene for wide ranges of potential application among the alkali metal ion batteries, Li-S batteries, hydrogen storage, supercapacitor, sensor and catalytic in hydrogen evolution, oxygen reduction, oxygen evolution, and CO2 electroreduction reaction. Finally, the challenges and outlooks in this promising field are featured on the basis of its current development.

Experimental investigation of the uncertainty principle for radial degrees of freedom

While the uncertainty principle for linear position and linear momentum,and more recently for angular position and angular momentum,is well established,its radial equivalent has so far eluded researchers.Here we exploit the logarithmic radial position,ln r,and hyperbolic momentum,PH,to formulate a rigorous uncertainty principle for the radial degree of freedom of transverse light modes.We show that the product of their uncertainties is bounded by Planck’s constant,Δln r·ΔPH≥h∕2,and identify a set of radial intelligent states that satisfy the equality.We illustrate the radial uncertainty principle for a variety of intelligent states,by preparing transverse light modes with suitable radial profiles.We use eigenmode projection to measure the corresponding hyperbolic momenta,confirming the minimum uncertainty bound.Optical systems are most naturally described in terms of cylindrical coordinates,and our radial uncertainty relation provides the missing piece in characterizing optical quantum measurements,providing a new platform for the fundamental tests and applications of quantum optics.

Quantum discord of thermal two-photon orbital angular momentum state:mimicking teleportation to transmit an image

We formulate a density matrix to fully describe two-photon state within a thermal light source in the photon orbital angular momentum(OAM)Hilbert space.We prove the separability,i.e.,zero entanglement of the thermal two-photon state.Still,we reveal the hidden quantum correlations in terms of geometric measures of discord.By mimicking the original protocol of quantum teleportation,we demonstrate that the non-zero quantum discord can be utilized to transmit a high-dimensional OAM state at the single-photon level.It is found that albeit the low fidelity of teleportation due to the inherent component of maximally mixed state,the information of all parameters that characterize the original state can still be extracted from the teleported one.Besides,we demonstrate that the multiple repetitions of the protocol,enable the transmission of a complex-amplitude light field,e.g.,an optical image,regardless of being accompanied with a featureless background.We also distinguish our scheme of optical image transmission from that of ghost imaging.

Strain engineering of ion migration in LiCoO_(2)

Strain engineering is a powerful approach for tuning various properties of functional materials. The influences of lattice strain on the Li-ion migration energy barrier of lithium-ions in layered LiCoO_(2) have been systemically studied using lattice dynamics simulations, analytical function and neural network method. We have identified two Li-ion migration paths, oxygen dumbbell hop (ODH), and tetrahedral site hop (TSH) with different concentrations of local defects. We found that Li-ion migration energy barriers increased with the increase of pressure for both ODH and TSH cases, while decreased significantly with applied tensile uniaxial c-axis strain for ODH and TSH cases or compressive in-plane strain for TSH case. Our work provides the complete strain-map for enhancing the diffusivity of Li-ion in LiCoO_(2), and therefore, indicates a new way to achieve better rate performance through strain engineering.

Frequency upconversion detection of rotational Doppler effect

We demonstrated an efficient scheme of measuring the angular velocity of a rotating object with the detection light working at the infrared regime.Our method benefits from the combination of second-harmonic generation(SHG)and rotational Doppler effect,i.e.,frequency upconversion detection of rotational Doppler effect.In our experiment,we use one infrared light as the fundamental wave(FW)to probe the rotating objects while preparing the other FW to carry the desired superpositions of orbital angular momentum.Then these two FWs are mixed collinearly in a potassium titanyl phosphate crystal via typeⅡphase matching,which produces the visible secondharmonic light wave.The experimental results show that both the angular velocity and geometric symmetry of rotating objects can be identified from the detected frequency-shift signals at the photon-count level.Our scheme will find potential applications in infrared monitoring.

Quantum twisted double-slits experiments:confirming wavefunctions'physical reality

Are quantum states real? This most fundamental question in quantum mechanics has not yet been satisfactorily resolved, although its realistic interpretation seems to have been rejected by various delayedchoice experiments. Here, to address this long-standing issue, we present a quantum twisted double-slit experiment. By exploiting the subluminal feature of twisted photons, the real nature of a photon during its time in flight is revealed for the first time. We found that photons' arrival times were inconsistent with the states obtained in measurements but agreed with the states during propagation. Our results demonstrate that wavefunctions describe the realistic existence and evolution of quantum entities rather than a pure mathematical abstraction providing a probability list of measurement outcomes. This finding clarifies the long-held misunderstanding of the role of wavefunctions and their collapse in the evolution of quantum entities.