Helium nanodroplets and trapped Bose–Einstein condensates as prototypes of finite quantum fluids

Abstract

Helium nanodroplets and trapped Bose-Einstein condensates in dilute atomic gases offer complementary views of fundamental aspects of quantum many-body systems. We discuss analogies and differences, stressing their common theoretical background and peculiar features. We briefly review some relevant concepts, such as the meaning of superfluidity in finite systems, the behavior of elementary excitations and collective modes, as well as rotational properties and quantized vorticity.

Spectroscopy and dynamics in helium nanodroplets

“…Moreover, the quantum nature and in particular the superfluid properties of the droplets allow one to investigate these quantum properties in a size-limited aggregate on the nanometer scale. Today the field of helium droplets is well established and several review articles have appeared during the last decade highlighting a variety of experimental as well as theoretical aspects [2,3,4,5,6,7,8,9,10,11,12,13,14]. In this paper, we will not attempt a comprehensive overview of the entire field because many experimental as well as theoretical approaches have already been reviewed, summarized and pointed out.…”

“…by up-to-date femtosecond techniques on the experimental side and on the theoretical side by significant progress in the understanding of the dynamics and energetic properties. We emphasize material that was not available when the several reviews were written that appeared in the Special Issue of the Journal of Chemical Physics [5,6,7,8,9] in late 2001.…”

Probing collective excitations in helium nanodroplets: Observation of phonon wings in the infrared spectrum of methane

“…The spectroscopy of dopants in helium nanodroplets gives access to the observation of collective excitations in a finite size Bose fluid. 3 The relevant theoretical concepts are described by Dalfovo and Stringari, 1 and Brink and Stringari. 4 The quantum nature of these systems becomes obvious at low temperature where the de Broglie wavelength exceeds the spacing between individual particles.…”

“…Helium nanodroplets provide a finite size laboratory to study the special effects of finite size quantum fluids. 1,2 Next to the rapidly growing field of Bose-Einstein condensates helium nanodroplets serve as prototypes of finite quantum fluids. The spectroscopy of dopants in helium nanodroplets gives access to the observation of collective excitations in a finite size Bose fluid.…”

Spectroscopy of free radicals and radical containing entrance-channel complexes in superfluid helium nanodroplets

“…The experimental details concerning the production of neat and doped helium droplets have been given in previous reviews [1][2][3][4][5][6] and their thermodynamic properties have been discussed [64][65][66]. Therefore, here we will only discuss the relevant details and specialties for embedding radicals in the droplets.…”