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001-es BibID:	BIBFORM004394
Első szerző:	Gulácsi Zsolt (fizikus)
Cím:	Exact many-electron ground states on diamond and triangle Hubbard chains / Zsolt Gulácsi, Arno Kampf, Dieter Vollhardt
Dátum:	2008
Megjegyzések:	We construct exact ground states of interacting electrons on triangle and diamond Hubbard chains. The construction requires (i) a rewriting of the Hamiltonian into positive semidefinite form, (ii) the construction of a many-electron ground state of this Hamiltonian, and (iii) the proof of the uniqueness of the ground state. This approach works in any dimension, requires no integrability of the model, and only demands sufficiently many microscopic parameters in the Hamiltonian which have to fulfill certain relations. The scheme is first employed to construct exact ground state for the diamond Hubbard chain in a magnetic field. These ground states are found to exhibit a wide range of properties such as flat-band ferromagnetism and correlation induced metallic, half-metallic or insulating behavior, which can be tuned by changing the magnetic flux, local potentials, or electron density. Detailed proofs of the uniqueness of the ground states are presented. By the same technique exact ground states are constructed for triangle Hubbard chains and a one-dimensional periodic Anderson model with nearest-neighbor hybridization. They permit direct comparison with results obtained by variational techniques for f-electron ferromagnetism due to a flat band in CeRh_3B_2.
Tárgyszavak:	Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban Elméleti Szilárdtestfizika
Megjelenés:	Progress of Theoretical Physics Supplement. - 176 (2008), p. 1 - 21. -
További szerzők:	Kampf, Arno Vollhardt, Dieter
Internet cím:	elektronikus változat DOI elektronikus változat
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001-es BibID:	BIBFORM016134
Első szerző:	Halász Zoltán (fizikus)
Cím:	The Effect of Disorder on Crackling Noise in Fracture Phenomena / Zoltán Halász, Gábor Timár, Ferenc Kun
Dátum:	2010
ISSN:	0375-9687
Megjegyzések:	We study the effect of disorder on crackling noise accompanying the fracture of heterogeneous materials. Two different types of system are considered: we analyze the three-point bending of a bar shaped specimen where the boundary and loading conditions ensure that crackling occurs during the propagation of a single crack; then we study a bundle of fibers where noise emerges as a consequence of spatially uncorrelated stick-slip rearrangements. We show that bursts characterizing the jerky propagation of a crack have a power law size distribution with an exponent which does not depend on the amount of disorder. Our calculations revealed that varying the amount of disorder in a stick-slip system, a phase-transition occurs: at high disorder stick-slip rearrangements occur in small bursts, while at low disorder macroscopic avalanches snap the system. Our investigations demonstrate that the relevance of disorder on crackling noise is strongly influenced by the presence or absence of stress concentrations in the system.
Tárgyszavak:	Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Progress Of Theoretical Physics Supplement. - 184 (2010), p. 385-399. -
További szerzők:	Timár Gábor Kun Ferenc (1966-) (fizikus)
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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