Achieving room-temperature valley polarization in two-dimensional (2D) atomic layers (2D materials) by substitutional doping opens new avenues of applications. Here, monolayer MoS 2 , when doped with vanadium at low (0.1 atomic %) concentrations, is shown to exhibit high spin-valley coupling, and hence a high degree of valley polarization at room-temperature. The atomic layers of MoS 2 (MS) and V-doped MoS 2 (VMS) are grown via the chemical vapor deposition-assisted method. The formation of new energy states near the valence band is confirmed from band gap calculations and also from the density functional theory-based band structure analyses. Time-reversal symmetry broken energy shift in the equivalent valleys is predicted in VMS, and the roomtemperature chirality-controlled photoluminescent (PL) excitation measurements indicate such a shift in valley exciton energies (∼35 meV). An enhanced valley polarization in VMS (∼42%) is observed in comparison to that in MS (<12%), while in MS, the chirality-controlled excitations did not show the difference in emission energies. Spin Hall effect of light-based optical rotation measurements indicate the asymmetric absorption among the two different chiralities of the incident light, hence supporting the existence of room-temperature valley polarization. This study opens possibilities of room-temperature opto-spintronics using stable 2D materials.

Hybrid ion capacitors (HICs) are emerging as promising energy-storage devices exhibiting the advantages of both batteries and supercapacitors. However, the difference in the electrodes' specific capacities and rate capabilities makes it extremely challenging to achieve optimum mass balancing for a full-cell HIC device. Here, we demonstrate a method to predict well-performing mass ratios of electrodes for a Na-HIC by analyzing the capacities of anodes and cathodes as a function of the actual current densities experienced by the individual electrodes. We employ a simple design tool, a "Ragone Plot Simulator", to predict specific energy and specific power on Ragone plots and study the performance trend of devices with varying electrode mass ratios. The validation of the proposed method is done based on the experimental data obtained from several hybrid ion capacitor devices reported in the literature, which closely matches with the simulated Ragone plots. Further, we exemplify the validity of our calculations by comparing the simulated Ragone plot with that of a Na-HIC fabricated using in-house-made carbon. This unique approach presents a simple, generalized, yet never reported, method, which could be employed as a design tool to guide the selection of optimized HIC devices for the intended applications.

The fast-emerging diverse applications using a variety of magnetic/non-magnetic heterostructure ultra-thin films warrant the sensitive characterization of the electrical, optical, and magnetic properties of the interface. As a practical alternate to the conventional magneto-optic Kerr effect (MOKE) method, we propose and demonstrate the spin-Hall effect of the light (SHEL)-based MOKE method with competitive sensitivity and scope for further improvement. The SHEL-MOKE technique is a versatile surface characterization tool for studying materials’ magnetic and dielectric ordering, which are extracted from the variations to the phase-polarization characteristics of a focused beam of light reflected at the interface, as a function of the applied magnetic field. Using this technique, we measure the magnetic field dependent complex Kerr angle and the coercivity in ultra-thin films of permalloy (Py) and at molybdenum disulfide (MoS[Formula: see text])—permalloy (MSPy) hetero-structure interfaces. A comprehensive theoretical model and simulation data are provided to strengthen the potential of this simple non-invasive optical method. The theoretical model is subsequently applied to extract the optical conductivity of non-magnetic ultra-thin layers of MoS[Formula: see text].

Magnetic/non-magnetic/heterostructured ultra-thin films' characterisation is highly demanding due to the emerging diverse applications of such films. Diverse measurements are usually performed on such systems to infer their electrical, optical and magnetic properties. We demonstrate that MOKE-based spin-Hall effect of light (SHEL) is a versatile surface characterization tool for studying materials' magnetic and dielectric ordering. Using this technique, we measure magnetic field dependent complex Kerr angle and the coercivity in ultra-thin films of permalloy (Py) and at molybdenum disulphide (MoS 2 ) -permalloy (MSPy) hetero-structure interfaces. The measurements are compared with standard magneto-optic Kerr effect (MOKE) studies to demonstrate that SHEL-MOKE is a practical alternative to the conventional MOKE method,with competitive sensitivity. A comprehensive theoretical model and simulation data are provided to further strengthen the potential of this simple non-invasive optical method. The theoretical model is applied to extract the optical conductivity and susceptibility of non-magnetic ultra-thin layers such as MoS 2 .