X(1835) Decay in the Fock-Tani Formalism

<div> <div>A shortcoming of presently available fragment-based methods is that electron correlation (if included) is described at the level of individual electrons, resulting in many redundant evaluations of the electronic relaxations associated with any given fluctuation. A generalized variant of coupled-cluster (CC) theory is described, wherein the degrees of freedom are fluctuations of fragments between internally correlated states. The effects of intra-fragment correlation on the inter-fragment interaction is pre-computed and permanently folded into the effective Hamiltonian. This article provides a high-level description of the CC variant, establishing some useful notation, and it demonstrates the advantage of the proposed paradigm numerically on model systems. A companion article shows that the electronic Hamiltonian of real systems may always be cast in the form demanded. This framework opens a promising path to build finely tunable systematically improvable methods to capture precise properties of systems interacting with a large number of other systems. </div> </div>

Download Full-text

Excitonic Coupled-cluster Theory: Part I, General Formalism

10.26434/chemrxiv.5330773.v1 ◽

2017 ◽

Author(s):

Yuhong Liu ◽

Anthony Dutoi

Keyword(s):

Electron Correlation ◽

Degrees Of Freedom ◽

Model Systems ◽

Coupled Cluster ◽

Effective Hamiltonian ◽

Coupled Cluster Theory ◽

Cluster Theory ◽

Companion Article ◽

High Level ◽

Fragment Interaction

<div> <div>A shortcoming of presently available fragment-based methods is that electron correlation (if included) is described at the level of individual electrons, resulting in many redundant evaluations of the electronic relaxations associated with any given fluctuation. A generalized variant of coupled-cluster (CC) theory is described, wherein the degrees of freedom are fluctuations of fragments between internally correlated states. The effects of intra-fragment correlation on the inter-fragment interaction is pre-computed and permanently folded into the effective Hamiltonian. This article provides a high-level description of the CC variant, establishing some useful notation, and it demonstrates the advantage of the proposed paradigm numerically on model systems. A companion article shows that the electronic Hamiltonian of real systems may always be cast in the form demanded. This framework opens a promising path to build finely tunable systematically improvable methods to capture precise properties of systems interacting with a large number of other systems. </div> </div>

Download Full-text

Electrocaloric effect in ferroelectric materials: from phase field to first-principles based effective Hamiltonian modeling

Materials Reports: Energy ◽

10.1016/j.matre.2021.100050 ◽

2021 ◽

pp. 100050

Author(s):

Jingtong Zhang ◽

Xu Hou ◽

Yajun Zhang ◽

Gang Tang ◽

Jie Wang

Keyword(s):

Phase Field ◽

First Principles ◽

Ferroelectric Materials ◽

Effective Hamiltonian ◽

Electrocaloric Effect

Download Full-text

Persistence of the spectral gap for the Landau–Pekar equations

Letters in Mathematical Physics ◽

10.1007/s11005-020-01350-5 ◽

2021 ◽

Vol 111 (1) ◽

Author(s):

Dario Feliciangeli ◽

Simone Rademacher ◽

Robert Seiringer

Keyword(s):

Initial Data ◽

Spectral Gap ◽

Effective Hamiltonian ◽

Adiabatic Theorem ◽

Strongly Coupled

AbstractThe Landau–Pekar equations describe the dynamics of a strongly coupled polaron. Here, we provide a class of initial data for which the associated effective Hamiltonian has a uniform spectral gap for all times. For such initial data, this allows us to extend the results on the adiabatic theorem for the Landau–Pekar equations and their derivation from the Fröhlich model obtained in previous works to larger times.

Download Full-text

Effective Hamiltonian for silicene under arbitrary strain from multi-orbital basis

Scientific Reports ◽

10.1038/s41598-021-86947-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Zhuo Bin Siu ◽

Mansoor B. A. Jalil

Keyword(s):

Tight Binding ◽

Spin Torque ◽

Spin Accumulation ◽

Effective Hamiltonian ◽

Fermi Surfaces ◽

Orbital Basis ◽

Lattice Symmetry ◽

Out Of Plane ◽

Coupling Parameters ◽

Spin Orbit Interactions

AbstractA tight-binding (TB) Hamiltonian is derived for strained silicene from a multi-orbital basis. The derivation is based on the Slater–Koster coupling parameters between different orbitals across the silicene lattice and takes into account arbitrary distortion of the lattice under strain, as well as the first and second-order spin–orbit interactions (SOI). The breaking of the lattice symmetry reveals additional SOI terms which were previously neglected. As an exemplary application, we apply the linearized low-energy TB Hamiltonian to model the current-induced spin accumulation in strained silicene coupled to an in-plane magnetization. The interplay between symmetry-breaking and the additional SOI terms induces an out-of-plane spin accumulation. This spin accumulation remains unbalanced after summing over the Fermi surfaces of the occupied bands and the two valleys, and can thus be utilized for spin torque switching.

Download Full-text