Point-Contact Study of Fast and Slow Two-Level Fluctuators in Metallic Glasses

Orbital Kondo-Effect From Tunneling Impurities

“…This might be due to some special origin of the TLS's but it is presently not well-understood. Finally, we discuss the results of a very recent measurement on amorphous break junctions by Keijsers et al 70 giving a very nice possibility to observe directly a single noncommutative TLS. In these experiments Keijsers et al found that the zero-bias anomaly G(V ) (R(V )) of the point contact fluctuated slowly between two values, G 1 (V ) and G 2 (V ).…”

“…Since the zero-bias anomaly is thought to be due to the fast two-level systems present in the contact area these fluctuations can be explained in terms of a slow fluctuator that influances the parameters of the fast TLS's. 70 One can also argue that the difference ∆G = G 1 (V ) − G 2 (V ) should be due to only a few possibly only one fast TLS with modified parameters. 71 Since it is the asymmetry parameter ∆ z of a TLS that is most sensitive to external stress, it should be possible to fit the difference ∆G(V ) by changing the splitting parameters ∆ i → ∆ ′ i for just a few TLS Kondo curves.…”

Stochastic resonance in a stochastic bistable system subject to additive white noise and dichotomous noise

“…Therefore, some new phenomena may occur: for example, the nonzero currents induced in stochastic ratchets [22] and the occurrence of even and odd spectral harmonics in the power spectral density of a bistable system [23][24][25][26]. Gora [13] studied the SR in a linear system with constant driving.…”

Dephasing in Metals by Two-Level Systems in the 2-Channel Kondo Regime

“…We further assume the saturation to be dominated by TLSs with D ren , T ‫ء‬ , T K , i.e., with D , 1 K , T K . Such parameters are reasonable, since experiment [22][23][24][25] and theory [16] suggest that a sizable fraction of D , 1 K TLSs indeed do also have T K . 1.…”

“…In the so-called NFL regime D ren , T , T K , the resulting effective 2CK model exhibits NFL behavior [13,21]. The zero-bias anomalies observed in recent years in nanoconstrictions made from a number of different materials, such as Cu [22], Ti [23], or metallic glasses [24,25], can be consistently explained by attributing them to fast TLSs in or near this 2CK NFL regime [26,27]. The Kondo temperatures of the relevant TLSs were deduced in [22][23][24] from the width of the zero-bias anomalies to be T K * 1 K, and in [25] the insensitivity of the anomalies to a high-frequency modulation of the bias voltage implied T K * 2 K.…”