Correlations in a band insulator

0337277 - FZÚ 2010 RIV US eng J - Journal Article
Sentef, M. - Kuneš, Jan - Werner, P. - Kampf, A. P.
Correlations in a band insulator.
[Korelace v pásovém izolátoru.]
Physical Review. B. Roč. 80, č. 15 (2009), 155116/1-155116/7. ISSN 1098-0121
Institutional research plan: CEZ:AV0Z10100521
Keywords : electronic correlations * dynamical mean-field theory * band insulator
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 3.475, year: 2009

We study a model of a covalent band insulator with on-site Coulomb repulsion at half filling using dynamical mean-field theory. Upon increasing the interaction strength the system undergoes a discontinuous transition from a correlated band insulator to a Mott insulator with hysteretic behavior at low temperatures. Increasing the temperature in the band insulator close to the insulator-insulator transition we find a crossover to a Mott insulator at elevated temperatures. Remarkably, correlations decrease the energy gap in the correlated band insulator. The gap renormalization can be traced to the low-frequency behavior of the self-energy, analogously to the quasiparticle renormalization in a Fermi liquid. While the uncorrelated band insulator is characterized by a single gap for both charge and spin excitations, the spin gap is smaller than the charge gap in the correlated system.

Model kovalentniho pasoveho izolatoru s localni coulombovskou interakci je studovan metodou dynamickeho stredniho pole. S rostouci silou interakce system prochazi skokovym prechodem do stavu Mottova izolatoru. Za pozornost stoji zjisteni, ze elektronove korelace vedou k zuzeni zakazaneho pasu. Renormalizace zakazaneho pasu je dane chovanim self-energie pri nizkych frekvencich, podobne jako dochazi k renormalizaci kvazicastic ve Fermiho kapaline. Zatimco neiteragujici pasovy izolator je charakterizovan pasem zakazanych energii o stejne velikosti pro spinove a nabojove excitace, v korelovanem izolatoru je zakazany pas pro spinove excitace uzsi nez pro excitace nabojove.
Permanent Link: http://hdl.handle.net/11104/0181306