Date:
Thu, 02/06/2022 - 11:00 to 12:00
Location:
Los Angeles Bld.
Abstract:
Glassy systems exhibit various universal anomalies compared to their crystalline counterparts,
manifested in their vibrational, thermodynamic, transport and strongly dissipative properties.
At the heart of understanding these phenomena resides the need to quantify glassy disorder,
self-generated during the non-equilibrium glass formation process, and to identify elementary
excitations that are associated with it. In this talk, I will review our recent progress in addressing these basic problems. I will first establish the existence of low-energy (soft) non-phononic excitations in glasses, which have been debated for decades. These low-energy glassy excitations feature spatial localization accompanied by power-law tails, and follow a universal gapless ω4 density of states (VDoS), to be contrasted with spatially-extended phonons and Debye’s phononic VDoS. I will then discuss the properties of the non-universal pre-factor of the ω4 VDoS and the non-equilibrium physics encapsulated in it. Finally, time permitting, I will discuss examples that demonstrate the importance of low-energy excitations
in the physics of glasses, e.g. in relation to the low-temperature specific heat and the fracture toughness. Open questions will be briefly mentioned.
Glassy systems exhibit various universal anomalies compared to their crystalline counterparts,
manifested in their vibrational, thermodynamic, transport and strongly dissipative properties.
At the heart of understanding these phenomena resides the need to quantify glassy disorder,
self-generated during the non-equilibrium glass formation process, and to identify elementary
excitations that are associated with it. In this talk, I will review our recent progress in addressing these basic problems. I will first establish the existence of low-energy (soft) non-phononic excitations in glasses, which have been debated for decades. These low-energy glassy excitations feature spatial localization accompanied by power-law tails, and follow a universal gapless ω4 density of states (VDoS), to be contrasted with spatially-extended phonons and Debye’s phononic VDoS. I will then discuss the properties of the non-universal pre-factor of the ω4 VDoS and the non-equilibrium physics encapsulated in it. Finally, time permitting, I will discuss examples that demonstrate the importance of low-energy excitations
in the physics of glasses, e.g. in relation to the low-temperature specific heat and the fracture toughness. Open questions will be briefly mentioned.