Two-Channel Kondo Physics due to As Vacancies in the Layered Compound ZrAs_{1.58}Se_{0.39}

We address the origin of the magnetic-field-independent -|A|T^{1/2} term observed in the low-temperature resistivity of several As-based metallic systems of the PbFCl structure type. For the layered compound ZrAs_{1.58}Se_{0.39}, we show that vacancies in the square nets of As give rise to the low-temperature transport anomaly over a wide temperature regime of almost two decades in temperature. This low-temperature behavior is in line with the nonmagnetic version of the two-channel Kondo effect, whose origin we ascribe to a dynamic Jahn-Teller effect operating at the vacancy-carrying As layer with a C_{4} symmetry. The pair-breaking nature of the dynamical defects in the square nets of As explains the low superconducting transition temperature T_{c}≈0.14  K of ZrAs_{1.58}Se_{0.39} compared to the free-of-vacancies homologue ZrP_{1.54}S_{0.46} (T_{c}≈3.7  K). Our findings should be relevant to a wide class of metals with disordered pnictogen layers.