Charge Carriers Localization Effect Revealed through Terahertz Spectroscopy of MXene: Ti3C2Tx

The transport properties of charge carriers in MXene, a promising material, have been studied using terahertz time-domain spectroscopy (THz-TDS) to examine its potential applications in optical and electronic devices. However, previous studies have been limited by narrow frequency ranges, which have hindered the understanding of the intrinsic mechanisms of carrier transport in MXenes. To address this issue, ultrabroadband THz-TDS with frequencies of up to 15 THz to investigate the complex photoconductances of MXene (Ti3C2Tx) films with different thicknesses are employed. The findings indicate that the electronic localization is substrate-dependent, and this effect decreases with an increase in the number of layers. This is attributed to the screening effect of the high carrier density in Ti3C2Tx. Additionally, the layer-independent photocarrier relaxations revealed by optical pump THz probe spectroscopy (OPTP) provide evidence of the carrier heating-induced screening effect. These results are significant for practical applications in both scientific research and various industries.

Electronic Localization Derived Excellent Stability of Li Metal Anode with Ultrathin Alloy

Lithium metal is an ideal anode for next-generation high-energy-density batteries. However, lithium dendrite growth has impeded its commercial application. Herein, fabricating Li-based ultrathin alloys with electronic localization and high surface work function via depositing Bi, Al, or Au metals on the surface of copper foil for in situ alloying with lithium is proposed. It is discovered that the electronic localization can induce self-smoothing effect of Li ions, as a result, significantly suppressing the growth of dendritic lithium. Meanwhile, the high surface work function can effectively alleviate side reactions between the electrolyte and lithium. With the as-obtained ultrathin alloys as anodes, excellent cycling performance is achieved. The half cells run stably after more than 120 cycles under high capacity of 4 mAh cm^-2 . The S||Bi/Cu-Li full cell delivers a specific capacity of 736 mAh g^-1 after 200 cycles. This work provides a new strategy for fabricating long-life and high-capacity lithium batteries.

Path integrals for electronic densities, reactivity indices, and localization functions in quantum systems

The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI) development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr’s quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions – all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving) many-electronic systems.