Abstract
In the presence of dipolar interactions the excitation spectrum of a Bose gas can acquire a local minimum. The corresponding quasiparticles are known as rotons. They are gaped and do not decay at zero temperature. Here we study the decay of rotons in one-dimensional Bose gases at low temperatures. It predominantly occurs due to the backscattering of thermal phonons on rotons. The resulting rate scales with the third power of temperature and is inversely proportional to the sixth power of the roton gap near the solidification phase transition. The hydrodynamic approach used here enables us to find the decay rate for quasiparticles at practically any momenta, with minimal assumptions on the exact form of the interparticle interactions. Our results are an essential prerequisite for the description of all the dissipative phenomena in dipolar gases and have direct experimental relevance.
Highlights
At low pressures and temperatures, helium-4 is a remarkable quantum liquid that is superfluid. Landau characterized the latter state by a dissipationless flow of macroscopic objects at low velocities [1]. Another particular feature of the superfluid helium is seen in its spectrum of elementary excitations
The corresponding quasiparticles are known as rotons and have wavelengths that practically coincide with the mean interparticle distance
In this paper we study the damping of energetic quasiparticles in a one-dimensional dipolar Bose gas
Summary
At low pressures and temperatures, helium-4 is a remarkable quantum liquid that is superfluid. Since the interaction between helium atoms is strong, the roton can be visualized as a yet undeveloped Goldstone mode due to an instability toward crystallization [2] Such a so-called supersolid state that unifies superfluidity with crystalline order has not been observed in helium, despite some controversies [3,4,5]. In this paper we study the damping of energetic quasiparticles (including rotons) in a one-dimensional dipolar Bose gas. This process is controlled by the backscattering of thermal phonons. Our results pave the way for a description of the postquench relaxation dynamics of a dipolar Bose gas [34]
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