Quantum one-dimensional materials at low temperature: Pre-critical effects, long-range correlations, and specific...

Area of Science:

• Condensed Matter Physics
• Statistical Mechanics
• Quantum Mechanics

Background:

• Ising's 1925 theory predicted no phase transitions in 1D systems at finite temperatures.
• Ising also identified a critical point at T=0K and low density, marked by diverging correlation length.
• Recent advances in synthesizing 1D van der Waals materials necessitate understanding their low-temperature behavior.

Purpose of the Study:

• To investigate the low-temperature and low-density behavior of a 1D system of spin-0 Lennard-Jones molecules (H2).
• To confirm Ising's prediction of a critical point at T=0K using advanced simulation techniques.
• To compare classical and quantum mechanical simulation results for correlation length and specific heat.

Main Methods:

• Classical and quantum mechanical path integral Monte Carlo (PIMC) simulations.
• Calculation of static pair correlation function, correlation length (ξ), and specific heats.
• Simulations conducted at temperatures down to T* = 0.01 and densities down to ρ* = 0.1.

Main Results:

• PIMC results show strong long-range fluctuations extending beyond 50 molecular diameters at low T and low ρ.
• Correlation length (ξ) appears to diverge as temperature approaches 0K, confirming Ising's critical point prediction.
• Specific heat diverges as temperature lowers toward absolute zero, indicating approach to a critical point.

Conclusions:

• The study strongly confirms Ising's prediction of a critical point at T=0K for 1D systems.
• Quantum effects significantly influence correlation length, which classical simulations do not capture.
• Observed phenomena are relevant to the development and understanding of one-dimensional van der Waals materials.