Terahertz phase slips in striped La2-xBaxCuO4

Interlayer transport in high-TC cuprates is mediated by superconducting tunneling across the CuO2 planes. For this reason, the terahertz frequency optical response is dominated by one or more Josephson plasma resonances and becomes highly nonlinear at fields for which the tunneling supercurrents approach their critical value IC. These large terahertz nonlinearities are in fact a hallmark of superconducting transport. Surprisingly, however, they have been documented in La2-xBaxCuO4 (LBCO) also above TC for doping values near x = 18 and interpreted as an indication of superfluidity in the stripe phase. Here, electric-field-induced second harmonic is used to study the dynamics of time-dependent interlayer voltages when LBCO is driven with large-amplitude terahertz pulses, in search of other characteristic signatures of Josephson tunneling in the normal state. We show that this method is sensitive to the voltage anomalies associated with 2 pi Josephson phase slips, which near x = 1 8 are observed both below and above TC. These results document a regime of nonlinear transport that shares features of fluctuating stripes and superconducting phase dynamics.

Automated summary

Interlayer transport in high-TC cuprates is mediated by superconducting tunneling, resulting in highly nonlinear terahertz frequency optical response. Surprisingly, nonlinearities have also been observed in certain doping values above TC, indicating superfluidity in the stripe phase. An electric-field-induced second harmonic method is used to study the voltage anomalies associated with Josephson phase slips in La2-xBaxCuO4 (LBCO) both below and above TC, revealing a regime of nonlinear transport with features of fluctuating stripes and superconducting phase dynamics.