Abstract
A new superconducting field-effect transistor (FET) in the vicinity of bandwidth-controlled Mott transition was developed using molecular strongly correlated system κ-(BEDT-TTF)2Cu[N(CN)2]Br [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene] laminated on CaF2 substrate. This device exhibited significant cooling-rate dependence of resistance below about 80 K, associated with glass transition of terminal ethylene group of BEDT-TTF molecule, where more rapid cooling through glass transition temperature leads to the decrease in bandwidth. We demonstrated that the FET properties such as ON/OFF ratio and polarity can be controlled by utilizing cooling rate. Our result may give a novel insight into the design of molecule-based functional devices.
Highlights
Molecular conductors κ-type (BEDT-TTF)2 X [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene (Figure 1a), X = anion] are interesting materials in terms of unconventional superconductivity neighboring Mott insulating state, which is similar to high critical temperature (TC ) cuprate superconductors [1,2]
Κ-(BEDT-TTF)2 Cu[N(CN)2 ]Cl, which is one of the most typical Mott insulators in this series of compounds, shows superconductivity under pressure of ca. 40 MPa [3]
In the present κ-Br field-effect transistor (FET), we found a remarkable cooling-rate dependence of FET properties such as ON/OFF ratio and field-effect polarity, which was not observed in previous FETs based on κ-BEDT-TTF salts
Summary
Molecular conductors κ-type (BEDT-TTF) X [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene (Figure 1a), X = anion] are interesting materials in terms of unconventional superconductivity neighboring Mott insulating state, which is similar to high critical temperature (TC ) cuprate superconductors [1,2]. They have two-dimensional (2D) conducting layers with strongly dimerized. BEDT-TTF molecules (Figure 1b,c) to form an effectively half-filled band structure, affording strong electron correlation Due to their flexible molecule-based crystal lattices, slight physical pressure or anion variation can control transfer integrals, bandwidth (that is anti-proportional to the electron correlation), to induce superconductivity. Κ-type BEDT-TTF system has been typically studied as bandwidth-controlled superconductor
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