Condensed Matter Seminars

The specific heat and elastic constants of metallic glasses show anomalies not seen in crystals. These anomalies result from low-energy vibrational excitations in the glass. We have measured the low-temperature heat capacity, the elastic constants, and the phonon density of states of both glassy and single-phase crystalline Pd₄₀Cu₄₀P₂₀. The specific heats of both alloys, plotted as C_P/T³ vs. T, show different humps (commonly known as "Boson Peaks"). The elastic constants of the crystal and glass have different T-dependence: the shear modulus of the glass varies as C'(T) = C'(0)[1 - AT], whereas that of the crystal varies as C'(T) = C'(0)[1 - BT² - DT⁴]. This suite of low-temperature measurements enabled us to identify the low-energy vibrational excitations responsible for these anomalies