Recent content by howl

Thanks for your answers! I know that there is anisotropy in many materials, what I want to know is when temperature goes up, resistance in x increases, while y no, is it usual?

Generally, a material is metal or insulator is simply determined by the gap. But if we view it in another way, to measure the resistance in different direction, says x and y, and there are usually different. And then measure the resistance change with temperature. Usually, the resistances goes...

There are some famous materials is determined as TI induced by SOC, like graphene and so on. But from some formula, for instance, Kane-Fu formula, they just need parities to get Z2 number. So I wonder if there is a known TI with weak soc.

Since we only know Gaussian integration, could one get Green's function numerically with interacting action. Usual perturbation theory is tedious and limited, could one get high accurate result with PC beyond perturbation?

Thanks a lot for your reply! I try to clear my two question once time, hope it helpful. First question is when one do perturbation, we could only consider low order perturbation, since high order would be smaller. But if one calculate Green's function by one order irreducible self-energy and...

First, is it suitable to solve a Green's function by one-order self-energy, since it only consider partial high order perturbation, so it's unclear that this calculation corresponding to which order perturbation. In other word, if one wants to use self-energy to get Green's function, he should...

It's helpful, thanks.

Someone says The fractional quantum Hall effect is an incompressible quantum liquid, what's the meaning?

Is the block spin scheme the most popular of them?

When one applies block spin scheme on Ising model, what's the value for block spin? If we set the average value for spin in a block, it should not be ±1 anymore. But if so, is the transfer matrix is still two dimensional?

Could an uniform external electrical field make an electron jump to a higher energy level?

In your link, there are some bands, for instance,Si. The electrons occupy the lowest bands under Fermi surface. For example, the band marked Gamma25', while Gamma15 and Gamma2' are empty. In QM, we should use up all eigenstates to build up a complete basis, then , if we only use Gamma25', could...

Usually, we only talk about the band near Fermi surface, but we know that atom could have infinite levels, so, for a solid, does it have infinite levels too? So, if we only talk about the levels near Fermi surface, are the eigenwavefunctions complete?

But it dosen't use group theory, and looks like no easy to generalize...

Could somebody write the guide for calculate the degeneracy of energy band by group theory? For instance, the valence band of Si and Ge in Gamma point. Thanks a lot!