PIRSA:19020071  ( MP4 Medium Res , MP3 , PDF ) Which Format?
Decay of correlations in long-range interacting systems at non-zero temperature

We study correlations in fermionic systems with long-range interactions in thermal equilibrium. We prove an upper-bound on the correlation decay between anti-commut-ing operators based on long-range Lieb-Robinson type bounds. Our result shows that correlations between such operators in fermionic long-range systems of spatial dimension $D$ with at most two-site interactions decaying algebraically with the distance with an exponent $alpha geq 2,D$, decay at least algebraically with an exponent arbitrarily close to $alpha$. Our bound is asymptotically tight, which we demonstrate by numerically analysing density-density correlations in a 1D quadratic (free, exactly solvable) model, the Kitaev chain with long-range interactions. Away from the quantum critical point correlations in this model are found to decay asymptotically as slowly as our bound permits.

Date: 13/02/2019 - 4:00 pm
Tech Note: First 15mins of lecture not captured due to a technical error.
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