Programme

P.46 -- Poster, VCTP-48

Date: Thursday, 3 August 2023

Time: 08:30 - 10:00

Excitonic insulator in the mass imbalance extended Falicov–Kimball model

Thi-Hau Nguyen (1), Thi-Hong-Hai Do (1) and Van-Nham Phan (2)

(1) Department of Physics, Hanoi University of Mining and Geology, Duc Thang, Bac Tu Liem, Hanoi, Vietnam; (2) Institute of Research and Development, Duy Tan University, 3 Quang Trung, Danang, Vietnam

Ground-state signatures of the excitonic insulator or excitonic condensation state in the mass imbalance extended Falicov-Kimball model in the presence of the electron-phonon correlation are investigated. Based on the unrestricted Hartree-Fock approximation, we have derived a set of self-consistent equations so the excitonic condensation order parameter is specified. The optical conductivity describing the low-energy excitations of the excitonic condensation state is considered in the Kubo linear response theory. At given sufficiently large electron-hole and electron-phonon couplings, phase diagrams show us the stability of the excitonic condensation state. The BCS-BEC crossover of the condensation state can be found in case of large mass imbalance. The BEC type of the condensate then disappears and one finds the simultaneous transition of the BCS condensate to the semimetal state by lowering the mass imbalance. Decreasing the electron-phonon coupling leads to the suppression of the excitonic condensate, specifically for the low mass imbalance. The influence of the electron-phonon interaction on the low-energy excitations of the excitonic condensate is also addressed in the signature of the real part of the optical conductivity.

Presenter: Nguyen Thi Hau