Communication: Fragment-based Hamiltonian model of electronic charge-excitation gaps and gap closure
Capturing key electronic properties such as charge excitation gaps within models at or above the atomic scale presents an ongoing challenge to understanding molecular, nanoscale, and condensed phase systems. One strategy is to describe the system in terms of properties of interacting material fragments, but it is unclear how to accomplish this for charge-excitation and charge-transfer phenomena. Hamiltonian models such as the Hubbard model provide formal frameworks for analyzing gap properties but are couched purely in terms of states of electrons, rather than the states of the fragments at the scale of interest. The recently introduced Fragment Hamiltonian (FH) model uses fragments in different charge states as its building blocks, enabling a uniform, quantum-mechanical treatment that captures the charge-excitation gap. These gaps are preserved in terms of inter-fragment charge-transferhopping integrals T and on-fragment parameters U(FH). The FH model generalizes the standard Hubbard model (a single intra-band hopping integral t and on-site repulsion U) from quantum states for electrons to quantum states for fragments. In this paper, we demonstrate that even for simple two-fragment and multi-fragment systems, gap closure is enabled once T exceeds the threshold set by U(FH), thus providing new insight into the nature of metal-insulator transitions. Finally, this result is in contrast to the standard Hubbard model for 1d rings, for which Lieb and Wu proved that gap closure was impossible, regardless of the choices for t and U.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Center for Materials at Irradiation and Mechanical Extremes (CMIME); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); Defense Threat Reduction Agency (DTRA)
- Grant/Contract Number:
- AC52-06NA25396; 2008LANL1026; HDTRA1-09-1-008
- OSTI ID:
- 1225985
- Alternate ID(s):
- OSTI ID: 1329873; OSTI ID: 1421243
- Report Number(s):
- LA-UR-15-24841
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Vol. 143 Journal Issue: 18; ISSN 0021-9606
- Publisher:
- American Institute of PhysicsCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Similar Records
Exact representation of the large-[ital U] Hubbard model and its application
Asymptotic Bethe-Ansatz results for a Hubbard chain with 1/sinh-hopping