Glass anomaly in the shear modulus of solid 4He

Area of Science:

• Condensed Matter Physics
• Materials Science
• Low-Temperature Physics

Background:

• Solid helium-4 (He-4) displays unusual mechanical properties at cryogenic temperatures.
• Previous torsional oscillator experiments observed anomalies in He-4's response.
• The shear modulus of solid He-4 shows a temperature-dependent stiffening at low temperatures.

Purpose of the Study:

• To explain the anomalous stiffening of the shear modulus in solid He-4 at low temperatures.
• To model this phenomenon using a glass susceptibility framework.
• To predict the frequency dependence of the shear modulus and dissipation.

Main Methods:

• Utilized a glass susceptibility model to describe the shear modulus behavior.
• Incorporated a temperature-dependent relaxation time, τ(T), into the model.
• Analyzed the crossover temperature T{X} where dynamics significantly slow down (ωτ(T{X})∼1).

Main Results:

• The proposed model successfully describes the stiffening of the shear modulus with decreasing temperature.
• Predictions indicate that the maximum change in shear modulus amplitude and dissipation peak height are independent of the applied frequency (ω).
• Calculations reveal that the temperature dependence of τ(T) qualitatively influences the shear modulus behavior.

Conclusions:

• The anomalous low-temperature shear modulus increase in solid He-4 can be attributed to dynamics described by glass susceptibility.
• The model predicts frequency-independent characteristics for key experimental observables.
• Further investigation into the specific temperature dependence of relaxation time is crucial for a complete understanding.