Maximum Energy Growth Rate in Dilute Quantum Gases

Abstract

In this letter we study how fast the energy density of a quantum gas can increase in time, when the inter-atomic interaction characterized by the $s$-wave scattering length $a_{\text{s}}$ is increased from zero with arbitrary time dependence. We show that, at short time, the energy density can at most increase as $\sqrt{t}$, which can be achieved when the time dependence of $a_{\text{s}}$ is also proportional to $\sqrt{t}$, and especially, a universal maximum energy growth rate can be reached when $a_{\text{s}}$ varies as $2\sqrt{\hslash t/(\pi m)}$. If $a_{\text{s}}$ varies faster or slower than $\sqrt{t}$, it is respectively proximate to the quench process and the adiabatic process, and both result in a slower energy growth rate. These results are obtained by analyzing the short time dynamics of the short-range behavior of the many-body wave function characterized by the contact, and are also confirmed by numerical solving an example of interacting bosons with time-dependent Bogoliubov theory. These results can also be verified experimentally in ultracold atomic gases.

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