We show that four heavy fermions interacting resonantly with a lighter atom (4+1 system) become Efimovian at mass ratio 13.279(2), which is smaller than the corresponding 2+1 and 3+1 thresholds. We thus predict the five-body Efimov effect for this system in the regime where any of its subsystem is non-Efimovian. For smaller mass ratios we show the existence and calculate the energy of a universal 4+1 pentamer state, which continues the series of the 2+1 trimer predicted by Kartavtsev and Malykh and 3+1 tetramer discovered by Blume. We also show that the effective-range correction for the light-heavy interaction has a strong effect on all these states and larger effective ranges increase their tendency to bind.
Bibliographical noteFunding Information:
This research was supported in part by the National Science Foundation under Grant No.NSF PHY-1125915 and received funding from the European Research Council (FR7/2007-2013 Grant Agreement No.341197), from a Chateaubriand Fellowship of the French Embassy in Israel, and from the Pazi Fund. We also acknowledge support by the IFRAF Institute.
© 2017 American Physical Society.