Sunday 19 January 2020

condensed matter - Bose-Einstein condensate in 1D


I've read that for a Bose-Einstein gas in 1D there's no condensation. Why this happenes? How can I prove that?



Answer



The claim is often that there is no condensation in $d<3$. The other answers are correct, but let's be clear, there are actually two assumptions present in the claim:





  1. Assume you have $N$ noninteracting bosons in $d$-dimensions in a hypervolume $L^d$




  2. Assume that these bosons have an energy-momentum relationship of $E(p) = Ap^s$.




Now, the way we calculate the critical temperature ($1/\beta_c$) for BEC requires satisfying the equation $$\int_0^\infty \frac{\rho(E)dE}{e^{\beta_c E}-1}=N$$


where $\rho(E)$ is the density of states. Whether this integral is convergent or not depends on the values of both $s$ and $d$. The details of the proof are up to you though. :)



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