Experimental realities refuting the existence of p=0 condensate in a system of interacting bosons : II. Spectroscopy of embedded molecules

TL;DR

This paper investigates superfluidity in helium-4 clusters with embedded molecules, showing that zero-momentum atoms are not necessary for superfluid behavior and identifying arrangements that enable free molecular rotation.

Contribution

It provides experimental insights refuting the necessity of p=0 condensate for superfluidity in interacting boson systems and details atomic arrangements facilitating free molecular rotation.

Findings

Atoms in clusters have non-zero momentum for confinement.

Superfluidity does not require zero-momentum atoms.

Certain atomic arrangements enable free molecular rotation.

Abstract

Experimental observation of superfluidity in a microscopic cluster, $M:(^4He)_x$, of a molecule ($M$) and $x$ number of $^4He$ atoms (with $x$ ranging from 1 to many) is qualitatively analyzed. It concludes that: (i) each $^4He$ atom in the cluster has to have non-zero momentum for its confinement to a space of size ($<$ the size of the cluster), (ii) superfluidity does not require atoms with zero momentum ($p=0$), and (iii) while all $^4He$ atoms in the cluster cease to have relative motions (hence the inter-atomic collisions), they retain a freedom to move coherently in order of their locations on a closed path around the rotor ($M$ plus few nearest $^4He$ atoms which follow the molecular rotation for their relatively strong binding with $M$). The analysis also identifies the basic arrangement of $^4He$ atoms which allows the rotor to have free rotation in the cluster.