WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
Browse
3 results
Search Results
Article Nagaoka Ferromagnetism in Semiconductor Artificial Graphene(IOP Publishing Ltd, 2026) Oztarhan, Gokhan; Potasz, Pawel; Guclu, A. D.We present the emergence of Nagaoka ferromagnetism in semiconductor-based artificial graphene with realistic Coulomb interaction using high-precision variational and diffusion Monte Carlo methods, complemented by exact diagonalization calculations of the generalized Hubbard model. We analyze models of armchair hexagonal geometries nanopatterned on GaAs quantum wells. Our results reveal a distinct magnetic phase transition driven by the absence/addition of a single electron at half-filling. This form of itinerant magnetism, predicted rigorously for the Hubbard model, remained unascertained in large scale realistic systems. We demonstrate that Coulomb scattering terms play a crucial role in stabilizing Nagaoka ferromagnetism, enabling the observation of the phase transition for system parameters near U/t approximate to 60.Article Quantum Monte Carlo Study of Artificial Triangular Graphene Quantum Dots(Amer Physical Soc, 2025) Kul, E. Bulut; Habibzadeh, Alireza; Cinar, M. N.; Guclu, A. D.We investigate the magnetic phases of semiconductor-based artificial triangular graphene quantum dots (TGQDs) with zigzag edges using variational and diffusion Monte Carlo methods. These systems serve as quantum simulators for bipartite lattices with broken sublattice symmetry, providing a platform to study the extended Hubbard model's emergent magnetic phenomena, including Lieb's magnetism at half filling, edge depolarization upon single-electron addition, and Nagaoka ferromagnetism. Our nonperturbative quantum Monte Carlo simulations, performed for finite-sized TGQDs modeled as nanopatterned GaAs quantum wells, with system sizes up to Ns = 61 lattice sites, reveal a transition from metallic to insulating regimes as a function of the quantum well radius rho, while preserving edge-polarized ground states at half filling. Notably, edge depolarization occurs upon single-electron doping in both metallic and insulating phases, in contrast to the Nagaoka ferromagnetism observed in hexagonal armchair geometries.Article Citation - WoS: 4Citation - Scopus: 3Quantum Monte Carlo Study of Semiconductor Artificial Graphene Nanostructures(AMER PHYSICAL SOC, 2023) Öztarhan, Gökhan; Güçlü, Alev Devrim; Kul, E. Bulut; Okçu, Emre; Guclu, A. D.Semiconductor artificial graphene nanostructures where the Hubbard model parameter U/t can be of the order of 100, provide a highly controllable platform to study strongly correlated quantum many-particle phases. We use accurate variational and diffusion Monte Carlo methods to demonstrate a transition from antiferromagnetic to metallic phases for an experimentally accessible lattice constant a = 50 nm in terms of lattice site radius rho, for finite-sized artificial honeycomb structures nanopatterned on GaAs quantum wells containing up to 114 electrons. By analyzing spin-spin correlation functions for hexagonal flakes with armchair edges and triangular flakes with zigzag edges, we show that edge type, geometry, and charge nonuniformity affect the steepness and the crossover rho value of the phase transition. For triangular structures, the metal-insulator transition is accompanied with a smoother edge polarization transition.