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.

Theory of a Planckian Metal

Abstract: We present a lattice model of fermions with N flavors and random interactions that describes a Planckian metal at low temperatures T→0 in the solvable limit of large N. We begin with quasiparticles around a Fermi surface with effective mass m^{*} and then include random interactions that lead to fermion spectral functions with frequency scaling with k_{B}T/ℏ. The resistivity ρ obeys the Drude formula ρ=m^{*}/(ne^{2}τ_{tr}), where n is the density of fermions, and the transport scattering rate is 1/τ_{tr}=fk_{B}T/ℏ; we find f of order unity and essentially independent of the strength and form of the interactions. The random interactions are a generalization of the Sachdev-Ye-Kitaev models; it is assumed that processes nonresonant in the bare quasiparticle energies only renormalize m^{*}, while resonant processes are shown to produce the Planckian behavior.

The role of effective mass of carrier in the photocatalytic behavior of silver halide-based Ag@AgX (X=Cl, Br, I): a theoretical study.

Abstract: The recent discovery of Ag@AgX (X=Cl, Br, I) plasmonic photocatalysts motivates us to elucidate the origin of the higher photocatalytic performance compared to commonly used TiO(2) -based materials. Herein, the electronic structure and effective masses of electrons at the conduction band minimum (CBM) and holes at the valence band maximum (VBM) are studied along different directions in the silver halide for the first time by means of first-principles calculations. It is revealed that the smaller effective mass of electrons at the CBM in silver halides contributes to the higher photocatalytic performance. The remarkable dependence of the effective mass of holes on the direction and the anion of the silver halide explains well the experimental observed morphology and anion dependence of photocatalytic activities of Ag@AgX. The crystal field splitting of the Ag 4d bands in the valance band of silver halides is found to be a main factor leading to the large effective mass of the photogenerated holes and consequently to a weaker transfer ability. A new crystal design and exerting strain along the coordinate axis are proposed as solutions to decrease the effective mass of holes. The present work may be helpful in exploring this novel class of silver halide-based photocatalysts.

Exciton-Phonon Interaction and Optical Spectra –Self-trapping, Zero-Phonon Line and Phonon Sidebands–

Abstract: Optical properties of interacting exciton-phonon system have been theoretically studied in terms of a simple model consisting of Frenkel excitons and Einstein oscillators. The problem is characterized by two non-dimensional parameters B and S representing the exciton band width and the interaction energy, respectively. Approximate solutions have been obtained through the diagonalization of the Hamiltonian in special sub-spaces, and they reasonably describe the behavior of the system for all values of B and S . Absorption and emission spectra and the effective mass of the composite particle vary from free exciton type to self-trapped exciton type as we go from B > S to B < S . The energy-momentum relation has been qualitatively studied below the one-phonon continuum, and the following new features have been found in the strong coupling region; (1) complete split-off of the lowest branch in the whole Brillouin zone, and (2) the split-off of the second discrete branch. Furthermore, a clue to the mechanism of...

Exploring heavy fermions from macroscopic to microscopic length scales

Abstract: Strongly correlated systems present fundamental challenges, especially in materials in which electronic correlations cause a strong increase of the effective mass of the charge carriers. Heavy fermion metals — intermetallic compounds of rare earth metals (such as Ce, Sm and Yb) and actinides (such as U, Np and Pu) — are prototype systems for complex and collective quantum states; they exhibit both a lattice Kondo effect and antiferromagnetic correlations. These materials show unexpected phenomena; for example, they display unconventional superconductivity (beyond Bardeen–Cooper–Schrieffer (BCS) theory) and unconventional quantum criticality (beyond the Landau framework). In this Review, we focus on systems in which Landau's Fermi-liquid theory does not apply. Heavy fermion metals and semiconductors are well suited for the study of strong electronic correlations, because the relevant energy scales (for charge carriers, magnetic excitations and lattice dynamics) are well separated from each other, allowing the exploration of concomitant physical phenomena almost independently. Thus, the study of these materials also provides valuable insight for the understanding — and tailoring — of other correlated systems. Heavy fermion systems are ideally suited to study strong electronic correlations. These fascinating materials are characterized by a clear separation of the relevant energy scales and may exhibit quantum critical points, non-Fermi-liquid behaviour and unconventional superconductivity coexisting or competing with magnetism.

Tunable Electronic Properties of Two-Dimensional Transition Metal Dichalcogenide Alloys: A First-Principles Prediction

Abstract: We investigated the composition-dependent electronic properties of two-dimensional transition-metal dichalcogenide alloys (WxMo1–xS2) based on first-principles calculations by applying the supercel...