ELFT HÍRADÓ

[Andras Palyi <palyi AT mail.bme.hu>]

Dear Colleagues, 

Next Monday Balazs Hetenyi will give a talk at the BME Exotic Quantum Phases 
seminar.

Speaker: Balazs Hetenyi (Bilkent & BME)
Title: Superfluid weight and polarization amplitude in the one-dimensional 
bosonic Hubbard model
Time: Oct 28, Monday, 14:00 (sharp)
Location: seminar room of the theory department (Department of Theoretical 
Physics, Building F, stairway III., 1111 Budapest, Budafoki ut 8.)

Abstract: "We calculate the superfluid weight and the polarization amplitude 
for the one-dimensional bosonic Hubbard model focusing on the strong-coupling 
regime. Other than analytic calculations we apply two methods: variational 
Monte Carlo based on the Baeriswyl wave function and exact diagonalization. 
The former gives zero superfluid response at integer filling, while the 
latter gives a superfluid response at finite hopping. From the polarization 
amplitude we derive the variance and the associated size scaling exponent. 
Again, the variational study does not produce a finite superfluid weight at 
integer filling (size scaling exponent is near one), but the Fourier 
transform of the polarization amplitude behaves in a similar way to the 
result of exact diagonalization, with a peak at small hopping, and suddenly 
decreasing at the insulator-superfluid transition. On the other hand, exact 
diagonalization studies result in a finite spread of the total position which 
increases with the size of the system. In the superfluid phase the size 
scaling exponent is two as expected. Importantly, our work addresses the 
ambiguities that arise in the calculation of the superfluid weight in 
variational calculations, and we comment on the prediction of Anderson about 
the superfluid response of the model at integer filling."

Best regards,
Andras Palyi