Quantum fluctuations-driven melting transitions in two-dimensional superconductors

Quantum fluctuations are pivotal in driving quantum phase transitions, exemplified by the quantum melting of Wigner crystals into Fermi liquids in electron systems. However, their impact on superconducting systems near zero temperature, particularly in the superconductor-insulator/metal transition, remains an open question. In this study, through electric transport measurements on the two-dimensional (2D) superconductor <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mrow><a:mo>(</a:mo><a:mi>SnS</a:mi><a:mo>)</a:mo></a:mrow><a:mrow><a:mn>1.17</a:mn></a:mrow></a:msub><a:msub><a:mi>NbS</a:mi><a:mn>2</a:mn></a:msub></a:mrow></a:math>, we demonstrate that quantum fluctuations induce vortex displacement from their mean position, leading to the quantum melting of vortex solid near zero temperature. Quantitative analysis suggests the magnetic field-induced anomalous metal originates from this quantum melting transition, with energy dissipation governed by quantum fluctuations-driven vortex displacements. Remarkably, further extending this analysis to various 2D superconductors yields the same results, and many properties of anomalous metal can be qualitatively understood within the framework of quantum melting. The connection between the quantum melting of vortex solids and dissipative anomalous metal opens a pathway toward understanding quantum phase transitions through vortex dynamics, providing insights on both fields.