虎扑电竞 虎扑电竞

A new route for exploration of nontrivial physical phenomena at two-dimensional materials

Iron selenide (FeSe) is an attracting superconducting material since the superconducting transition temperature (T_c) is enhanced from 8 K in bulk form toward 65 K in one-monolayer form.

However, systematic thickness dependence of electrical measurement has been difficult to address.

A team of researchers at Tohoku University's Institute for Materials 虎扑电竞 (IMR), has realized layer-by-layer etching in superconducting FeSe films down to approximately one-monolayer about 0.6 nm using classical electrochemical reaction in electric-double-layer transistor configuration.

As the thickness of the films becomes thin, the superconducting transition temperature (T_c) is increased from bulk value (8 K) to about 40 K. In addition, the research group unveils that by combining with an electrostatic charging effect, the high-T_c transition can be induced in 10-nm thick condition (20 monolayers), which had been limited in one/two-monolayers so far.

The development of this etching technique will pave the way for the exploration of nontrivial physical phenomena in atomically thin two-dimensional films. This had previously been difficult to address by conventional methods.

This work was published in Nature Physics online on Nov 2, 2015.

Figure: Schematic of electric-double-layer transistor device and electrochemical reaction on FeSe surface. (Left) Device structure of electric-double-layer transistor with FeSe channel deposited on oxide substrate. (Right) One-monolayer FeSe is realized by electrochemical etching where Fe and Se ions are dissolved into ionic liquid.

Publication Information

Authors: J. Shiogai, Y. Ito, T. Mitsuhashi, T. Nojima and A. Tsukazaki
Title: Electric-field-induced superconductivity in electrochemically etched ultrathin FeSe films on SrTiO₃ and MgO
Journal: Nature Physics
DOI: 10.1038/nphys3530