Voltage-Induced Hysteretic Resistance in Nematic Order of SmFeAsO

Point-contact spectroscopy has been utilized to study SmFeAsO, the parent compound of the “1111” iron superconductors. A bias voltage drives the point contact through antiferromagnetic and structural transitions via the ballistic Joule heating effect. Surprisingly, the bias voltage also induces a hysteretic conductance only in the temperature range of the nematic order, while there is no such behavior in the temperature-dependent resistance. The larger the maximum bias voltage, the bigger the conductance changes in the hysteresis, but always exclusively in the nematic order regime. The voltage-driven conductance hysteresis, which is not affected by a magnetic field of 5 T, suggests the nematic order in the SmFeAsO sample may be from an electronic origin and can be controlled by a voltage.