4European Theoretical Spectroscopy Facility

Experimental evidence for two-level systems Anomalies in low-temperature behavior of amorphous materials [1] Noise in superconducting circuits [2] Model of two-level systems Among all models proposed for explanation to account for anomalious thermal data for amorhous materials, the most successful one is the model of two-level systems (TLSs) [1]. In this model, atoms occupying two adjacent minima of the double-well potential tunnel quantum mechanically to the other, leading to the splitting of the ground state. The energy splitting of TLS TLS that incluence the properties at temperature T ~ 1 K have. For an Al atom, ~ 1013 s-1 and d ~ 0.5 Å, we get V0 ~ 5- 10 meV. Assuming the distribution of energy splittings of two-level systems in energy is constant and has the density n0, the heat capacity of amorphous solids at low temperature can be found as [1