Xiaoyi Han

Anomalous ac dielectric response and carrier state of c-axis oriented La2−xSrxCuO4 films

Abstract In order to study the “fractional Hall effect model” of the carrier state of high temperature superconductors, we measured the x dependence of the capacitance C t of multilayer structure Pd/La 2− x Sr x CuO 4 /(100)SrTiO 3 /Pd. A strong correspondence is found between the x - C t relationship and the filling factor ν dependence of the system energy in the fractional quantum Hall effect.

New FET using the superconducting phase transition of a high temperature oxide superconductor

A theoretical study is made on a superconductor FET based on the controllability of the transition temperature of an ultra-thin film of high temperature oxide superconductor by way of the field-effect modulation of the carrier density. The dependence of the device characteristics on the number of the unit-cell layers is clarified.

Anomalous dielectric effect of La/sub 2-x/Sr/sub x/CuO/sub 4/

The dielectric response of c-axis oriented La/sub 2-x/Sr/sub x/CuO/sub 4/ film is experimentally studied using Pd/La/sub 2-x/Sr/sub x/CuO/sub 4//(100)SrTiO/sub 3//Pd multi-layer structure. Anomalous capacitance increase is observed at Sr doping level x/spl ap/1/2/sup n/, where the drop of resistivity in bulk La/sub 2-x/Sr/sub x/CuO/sub 4/ in normal state has been reported.

Observation of single-electron charging effect in BiSrCaCuO granular thin films

The electrical field effect of highly resistive BiSrCaCuO granular thin films was studied. In order to form a uniform granular structure, BiSrCaCuO thin films where deposited on SrTiO3(110) substrates. When the films have relatively high room-temperature sheet resistance, the insulating transition at low temperatures and the charging effect are observed, which may be due to the single-electron tunneling effect in the array of small intergrain junctions.

The electric field effect in a BSCCO thin film

The electric field effect in a Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ (BSCCO) thin film was studied using a FET structure, the channel of which was made of a BSCCO thin film sputtered on a

Anomalous electric characteristic of La2−xSrxCuO4 at x=1/4n

The resistivity of LSCO materials drops sharply at χ≈4-n from, low up to room temperature. Anomalous dielectric response of LSCO film at χ≈4-n and χ≈2x4-n is found along c axis. The capacitanceC t of multi-layer structure Pd/LSCO/STO/Pd increases at thex values exceeding the capacitanceCsto of Pd/STO/Pd structure from low to room temperature, where effective dielectric constant of the conductive normal state is consideed to be negative. TheC-V measurement reveals the existence of “critical voltage” in the anomalous dielectric property.

Experimental Study of HTS FET Device Based on Superconducting Phase Transition

An experimental study is made on HTS FET device based on superconducting phase transition. The sample of the three-terminal device is made of BSCCO thin film formed on (100) MgO substrate with SrTiO 3 gate-insulating layer. Appreciable conduction modulation is caused by the field effect with the modulation of superconducting phase transition at helium temperature.