Electrochemical Control of Copper Intercalation into Nanoscale Bi₂Se₃

Intercalation of exotic atoms or molecules into the layered materials remains an extensively investigated subject in current physics and chemistry. However, traditionally melt-growth and chemical interaction strategies are either limited by insufficiency of intercalant concentrations or destitute of accurate controllability. Here, we have developed a general electrochemical intercalation method to efficaciously regulate the concentration of zerovalent copper atoms into layered Bi₂Se₃, followed by comprehensive experimental characterization and analyses. Up to 57% copper atoms (Cu_6.7Bi₂Se₃) can be intercalated with no disruption to the host lattice. Meanwhile the unconventional resistance dip accompanied by a hysteresis loop below 40 K, as well as the emergence of new Raman peak in Cu_<i>x</i>Bi₂Se₃, is a distinct manifestation of the interplay between intercalated Cu atoms with Bi₂Se₃ host. Our work demonstrates a new methodology to study fundamentally new and unexpected physical behaviors in intercalated metastable materials