Effective mass (solid-state physics)

About: Effective mass (solid-state physics) is a research topic. Over the lifetime, 12539 publications have been published within this topic receiving 295485 citations.

Large effective mass and interaction-enhanced Zeeman splitting of K -valley electrons in MoSe 2

Abstract: We study the magnetotransport of high-mobility electrons in monolayer and bilayer ${\mathrm{MoSe}}_{2}$, which show Shubnikov--de Haas (SdH) oscillations and quantum Hall states in high magnetic fields. An electron effective mass of $0.8{m}_{e}$ is extracted from the SdH oscillations' temperature dependence; ${m}_{e}$ is the bare electron mass. At a fixed electron density the longitudinal resistance shows minima at filling factors (FFs) that are either predominantly odd, or predominantly even, with a parity that changes as the density is tuned. The SdH oscillations are insensitive to an in-plane magnetic field, consistent with an out-of-plane spin orientation of electrons at the $K$ point. We attribute the FF parity transitions to an interaction enhancement of the Zeeman energy as the density is reduced, resulting in an increased Zeeman-to-cyclotron energy ratio.

Molecular wires: guiding the super-exchange interactions between two electrodes

Abstract: After discussing experimental works on the measurement of the conductance of a metal–molecule–metal tunnel junction with many down to a few molecules and down to only one molecule in the junction, we propose a comprehensive way of understanding the electron transport phenomenon through such a junction. The dependence of the junction conductance on the length of the molecule(s) is explained starting from the quantum super-exchange electron transfer phenomenon up to the effective mass of the tunnelling electrons in the coherent limit. This super-exchange mechanism results from the electronic coupling between the two electrodes introduced by the molecule(s). The molecular wire guides this interaction better than the electronic coupling through vacuum between the two electrodes of the junction. Dephasing and thermal effects during the electron transfer events along the molecular wire are described using a density matrix formalism. The implication of our understanding of this through junction electronic transport is described starting from hybrid molecular electronics towards mono-molecular electronics.

Photoemission evidence for a Mott-Hubbard metal-insulator transition in VO 2

Abstract: The temperature (T) dependent metal-insulator transition (MIT) in VO2 is investigated using bulk sensitive hard x-ray (� 8 keV) valence band, core level, and V 2p-3d resonant photoemission spectroscopy (PES). The valence band and core level spectra are compared with full-multiplet cluster model calculations including a coherent screening channel. Across the MIT, V 3d spectral weight transfer from the coherent (d 1 C final) states at Fermi level to the incoherent (d 0 +d 1 L final) states, corresponding to the lower Hubbard band, lead to gap-formation. The spectral shape changes in V 1s and V 2p core levels as well as the valence band are nicely reproduced from a cluster model calculations, providing electronic structure parameters. Resonant-PES finds that the d 1 L states resonate across the V 2p-3d threshold in addition to the d 0 and d 1 C states. The results support a Mott-Hubbard transition picture for the first order MIT in VO2. PACS numbers: 79.60.-i, 71.30.+h VO2, a d 1 electron system, exhibits a sharp first-order metal-insulator transition (MIT) as a function of temperature (T), at TMI = 340 K. 1 The high-T metal phase has a rutile (R) structure, while the low-T insulating phase has a monoclinic (M1) structure with zig-zag type pairing of V atoms along the c-axis. 2 Magnetically, the metallic R phase shows enhanced susceptibility (�) with an effective mass m ∗ /m � 6, while the insulating M1 phase is non

Analytic model of direct tunnel current through ultrathin gate oxides

Abstract: A theoretical model for tunnel leakage current through 1.65–3.90-nm-thick gate oxides in metal-oxide-semiconductor structures has been developed. The electron effective mass in the oxide layer and the Fermi energy in the n+ poly-Si gate are the only two fitting parameters. It is shown that the calculated tunnel current is well fitted to the measured one over the entire oxide thickness range when the nonparabolic E-k dispersion relationship for the oxide band gap is employed. The electron effective mass in the oxide layer tends to increase as the oxide thickness decreases to less than 2.80 nm presumably due to the existence of compressive stress in the oxide layer near the SiO2/Si(100) interface.