ELFT HÍRADÓ

[Kormos Márton <kormos.marton AT ttk.bme.hu>]

MEGHÍVÓ

BME Elméleti Fizika Szeminárium,

szept. 11. péntek 10:15,

1111 Budapest, Budafoki út 8., BME F III. magasföldszint 01.,
Elméleti Fizika Tanszék szemináriumi szoba

Oroszlány László (ELTE Komplex Rendszerek Fizikája Tanszék, Wigner Fizikai 
Kutatóközpont)
AKLT Hamiltonian from Hubbard tripods

We investigate how the spin-1 Affleck-Kennedy-Lieb-Tasaki (AKLT) Hamiltonian 
can emerge from a microscopic fermionic model based on half-filled Hubbard 
tripods. We first show that a single tripod hosts a robust 
threefold-degenerate low-energy manifold corresponding to an effective S=1 
degree of freedom. This manifold prevails over a broad range of interactions 
and remains stable against moderate disorder. We then combine exact 
diagonalization with fourth-order quasi-degenerate perturbation theory to 
derive an effective bilinear-biquadratic spin model for a pair of coupled 
tripods and identify coupling regimes where the target ratio is approached. 
In particular, tuning leg-center hopping together with two 
symmetry-inequivalent leg-leg hoppings yields the characteristic 
singlet-triplet degeneracy associated with a biquadratic-to-bilinear ratio 
close to 1/3. Extending the analysis to three tripods, we compare 
nonequivalent coupling geometries and find a strategy that suppresses 
unwanted longer-range and multispin terms while preserving the target 
nearest-neighbor couplings in the weak-coupling regime. These results 
establish a concrete bottom-up route from Hubbard clusters to 
valence-bond-solid spin physics in tunable quantum-dot arrays.

Minden érdeklődőt szeretettel várunk.

A további program megtekinthető itt: https://physics.ttk.bme.hu/theoryseminars

Kormos Márton
szemináriumi koordinátor