On van der Waals friction between half-spaces at low temperature

Area of Science:

• Condensed Matter Physics
• Quantum Mechanics
• Nanoscale Tribology

Background:

• Understanding nanoscale friction is crucial for designing advanced materials and devices.
• The van der Waals regime governs interactions between closely spaced surfaces, neglecting relativistic and retardation effects.
• Drude-modelled half-spaces with weak dissipation provide a simplified yet relevant system for studying surface interactions.

Purpose of the Study:

• To determine the frictional power loss (P) and drag force (F) per unit area between two Drude-modelled half-spaces.
• To analyze the dependence of friction on relative speed (u), gap width (ζ), and temperature (T).
• To investigate the energy increment distribution resulting from friction-induced dissipation.

Main Methods:

• Utilizing nonrelativistic quantum mechanics with adiabatic and perturbative methods.
• Considering a low initial temperature regime where τ ≡ k(B)T/ħω(S) << 1.
• Analyzing two limiting cases: ν ≡ u/ω(S)ζ << 1 and ν >> 1, as well as fixed non-zero temperatures.

Main Results:

• At zero temperature, power loss P scales with u(4)/ζ(6) for low speeds (ν << 1) and 1/uζ for high speeds (ν >> 1).
• At non-zero temperatures, a temperature-dependent component proportional to u(2)T(2)/ζ(4) dominates at low speeds.
• The frequency distribution of friction-induced energy increments was found to be non-thermal.

Conclusions:

• The calculated friction dynamics are consistent with quantum electrodynamics-based approaches in the nonretarded limit.
• The non-thermal nature of energy increments suggests potential limitations in current theories for dissipative materials, like the Huttner-Barnett theory.
• This study provides fundamental insights into nanoscale frictional forces and energy dissipation mechanisms.