Dislocation-position fluctuations in solid 4He as collective variables in a quantum crystal

Quantum behavior at mesoscopic length scales is of significant interest, both from a fundamental-physics standpoint, as well as in the context of technological advances. In this light, the description of collective variables comprising large numbers of atoms, but nevertheless displaying non-classical behavior, is a fundamental problem. Here, we show that an effective-Hamiltonian approach for such variables, as has been applied to describe the quantum behavior of coupled qubit/oscillator systems, can also be very useful in understanding intrinsic behavior of quantum materials. We consider lattice dislocations - naturally occurring mesoscopic line defects in crystals - in the prototypical bosonic quantum crystal, solid He-4. For this purpose, we map fully atomistic quantum simulations onto effective one-dimensional Hamiltonians in which the collective dislocation-position variables are represented as interacting, massive quantum particles. The results provide quantitative understanding of several experimental observations in solid He-4.

Automated summary

Quantum behavior at mesoscopic length scales is of great interest and has implications for both fundamental physics and technological advancements. This study demonstrates that an effective-Hamiltonian approach used to describe quantum behavior in qubit/oscillator systems can also be applied to understand the intrinsic behavior of quantum materials. By mapping atomistic quantum simulations onto one-dimensional effective Hamiltonians, the study provides quantitative insights into experimental observations in solid He-4.