Influence of the nature of confinement on the melting of Wigner molecules in quantum dots

TL;DR

This study compares quantum and thermal melting of two-dimensional Wigner molecules in quantum dots, revealing that confinement symmetry does not significantly influence the quantum crossover, with defects playing different roles in each melting process.

Contribution

It uncovers the distinct mechanisms of quantum and thermal melting in Wigner molecules and shows that confinement symmetry has minimal impact on the quantum crossover scale.

Findings

Quantum and thermal melting mechanisms are complementary.

Confinement symmetry does not significantly affect the quantum crossover.

Defects have different roles in quantum versus thermal melting.

Abstract

We analyze the quantum melting of two-dimensional Wigner molecules (WM) in confined geometries with distinct symmetries and compare it with corresponding thermal melting. Our findings unfold complementary mechanisms that drive the quantum and thermal crossovers in a WM and show that the symmetry of the confinement plays no significant role in determining the quantum crossover scale $n_X$. This is because the zero-point motion screens the boundary effects within short distances. The phase diagram as a function of thermal and quantum fluctuations determined from independent criteria is unique, and shows "melting" from the WM to both the classical and quantum "liquids." An intriguing signature of weakening liquidity with increasing temperature, $T$, is found in the extreme quantum regime. The crossover is associated with production of defects. However, these defects appear to play distinct roles in driving the quantum and thermal "melting." Our study will help comprehending melting in a variety of experimental traps - from quantum dots to complex plasma.