講演者： Seiji Yunoki 氏（SISSA/ISAS, Italy)
日時： ３月　　９日（木）　　午後４時３０分から
場所： 青山学院大学　理工学部（相模原キャンパス）Ｌ棟６階　Ｌ６０３室

題目： 「Wave function description of Mott insulator」

要旨：
It has been well known that a variational approach is a very powerful 
theoretical tool to study complex classical and quantum many-body systems. 
In this talk, I will address a seemingly very simple question as to how to 
describe a Mott insulator for a single-band electronic lattice model by a 
simple quantum many-body wave function, and present a variational paradigm 
to understand the physical properties close to a Mott insulating state. 
Here a Mott-insulator is an insulating state with one electron per unit cell 
and without breaking any spatial symmetry. 

Using Feynman's f-sum rule, it is first argued that a singular
density-density 
Jastrow factor is an essential ingredient included in the wave function. 
It is then demonstrated that with this wave function one can correctly 
reproduce all the known low-energy properties (even from Luttinger liquid 
to Mott insulator) of the one dimension Hubbard model. 

To gain better insight on the quantum many-body state described by this wave 
function, it is shown that the state can be interpreted as a quantum version 
of a neutral classical Coulomb gas model at finite temperatures, where the 
positive charges correspond to the sites with doubly occupied sites 
(``doublons'') and the negative sites to the empty sites (``holons''). 
It is therefore expected that in two dimensions this wave function can 
display a Kosterlitz-Thouless like transition. I will show that from our 
numerical simulations this is indeed the case, and argue that the 
two-dimensional Mott-insulator metal transition can be unconventional. 


References
[1] M. Capello, F. Becca, S. Yunoki, M. Fabrizio, and S. Sorella, Phys. Rev. 
    B. 72, 085121 (2005).
[2] M. Capello, F. Becca, S. Yunoki, and S. Sorella, cond-mat/0509062 (2005).


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共催：　青山学院大学　理工学会