Abstract
The orbital two-channel Kondo effect displaying exotic non-Fermi liquid behaviour arises in the intricate scenario of two conduction electrons compensating a pseudo-spin-1/2 impurity of two-level system. Despite extensive efforts for several decades, no material system has been clearly identified to exhibit all three transport regimes characteristic of the two-channel Kondo effect in the same sample, leaving the interpretation of the experimental results a subject of debate. Here we present a transport study suggestive of a robust orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films, as evidenced by a magnetic field-independent resistivity upturn with a clear transition from logarithmic- to square-root temperature dependence and deviation from it in three distinct temperature regimes. Our results also provide an experimental indication of the presence of two-channel Kondo physics in a ferromagnet, pointing to considerable robustness of the orbital two-channel Kondo effect even in the presence of spin polarization of the conduction electrons.
Highlights
The orbital two-channel Kondo effect displaying exotic non-Fermi liquid behaviour arises in the intricate scenario of two conduction electrons compensating a pseudo-spin-1/2 impurity of two-level system
The orbital 2CK effect from two-level systems (TLSs) is manifested in electrical transport by a unique temperature (T) dependence in resistivity with three distinct T regimes (Fig. 1b): a low-T upturn characterized by DrxxBlnT for T4TK, followed by non-Fermi liquid (NFL) behaviour (DrxxBT1/2) for TD ( 1⁄4 D2/TK)oTooTK and deviation from T1/2 dependence upon further cooling[11,12]
The NFL behaviour was reported in Cu point contacts (PCs) and glassy ThAsSe single crystal[20,21,22,23], their small D prevented the observation of possible breakdown of the T1/2 behaviour at lower T
Summary
The orbital two-channel Kondo effect displaying exotic non-Fermi liquid behaviour arises in the intricate scenario of two conduction electrons compensating a pseudo-spin-1/2 impurity of two-level system. We present a transport study suggestive of a robust orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films, as evidenced by a magnetic field-independent resistivity upturn with a clear transition from logarithmic- to square-root temperature dependence and deviation from it in three distinct temperature regimes. Upadhyay et al.[24] observed the NFL behaviour and the low-energy restoration of the FL in conductance spectroscopy of Ti PCs, but there was no indication of a crossover to logarithmic dependence at high energies. Present theories expect an imbalance in the channel population to produce a crossover to FL behaviour at low temperatures[25], a magnetic field of up to 14 (5) T did not affect the NFL behaviour in ThAsSe Neither shows a T1/2 dependence characteristic of 2CK effect, possibly because of their low TK, large TD and partial polarization of the conduction electrons
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