PRESSURE CONTROL OF ORGANIC CONDUCTOR-DISCOVERY OF NEW TYPE OF NARROW GAP SEMICONDUCTORS

有机导体的压力控制——新型窄间隙半导体的发现

• 批准号: 10304031
• 负责人: KAJITA Koji
• 金额: $ 4.1万
• 依托单位: TOHO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A).
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10304031/
• 关键词: ORGANIC CONDUCTOR; MAGNETO-TRANSPORT; HALLEFFECT; NARROW GAP SEMICONDUCTOR; PRESSURE EFFECT; UNIAXIAL STRAIN; ナローギャップ半導体

Many organic conductors exhibit temperature-independent conductivity. Usually, they are considered to be dirty metals of which the electrical conduction is governed by impurity scattering. One of the main results of this investigation is the finding of pure organic conductors which shows temperature independent conductivity. In those conductors, both carrier density and mobility vary strongly with temperature. Nevertheless, we see temperature independent conduction because the effect of the change in the density and mobility just cancel out. Up to now, we know no other materials with such curious character both among organic and inorganic conductors. According to the density change at low temperatures, we found that they are semiconductors with extremely narrow energy gap.Organic conductors such as α-(BEDT-TTF)_2I_3, α-(BEDT-TSeF)_2I_3, O-(BEDT-TTF)_2I_3 and α-(BEDT-STF)_2I_3 belongs to this category of materials in case they are placed under high pressures.Another characteristic behavior of those materials is observed at low temperature under magnetic field. The property of carriers varies with increasing field. There are three steps of change. At low field limit, carriers have the mass of about 0.02m. where m is the free electron mass. In the intermediate field, the mass rises to a value close to m. In the high fields such as 10T, carrier mass looks to be much heavier.

许多有机导体具有与温度无关的导电性。通常，它们被认为是肮脏的金属，其导电受杂质散射的影响。这项研究的主要结果之一是发现了纯有机导体，它显示出与温度无关的导电性。在这些导体中，载流子密度和迁移率都随温度变化很大。然而，我们看到温度无关的传导，因为密度和迁移率的变化的影响刚刚抵消。到目前为止，在有机和无机导体中，还没有其他材料具有如此奇特的性质。根据低温下的密度变化，我们发现它们是具有极窄能隙的半导体。α-(BEDT-TTf)_2I_3、α-(BEDT-TSeF)_2I_3、O-(BEDT-TTf)_2I_3和α-(BEDT-STF)_2I_3等有机导体在高压下属于这类材料。载流子的性质随场的增大而变化。改变有三个步骤。在低场极限下，载流子的质量约为0.02米。式中，m是自由电子质量。在中场，载流子质量增加到接近m的值。在10T这样的高场，载流子质量看起来要重得多。

项目成果

西尾豊,田村雅史,梶田晃示,青沼,沢,加藤,小林: "Thermodynamical study of (Dme-DCNQI)_2Cu system -Mechanism of Reentrent Metal-Insulator Transition"Journal of the Physical Society of Japan. (印刷中)69・5. (2000)

Yutaka Nishio、Masashi Tamura、Koji Kajita、Aonuma、Sawa、Kato、Kobayashi：“(Dme-DCNQI)_2Cu 体系的热力学研究 - 凹入金属-绝缘体转变的机制”日本物理学会杂志（出版中）69。・5.（2000）

H.Mori: "Bandwidth and band filling control in Organic conductors"Syntnetic Metals. (in press).

H.Mori：“有机导体中的带宽和带填充控制”合成金属。

N.Tajima: "Anomalous Magnetotransport of a Highly Mobile electron system in α-(BEDT-TTF)_2I_3"Synhtetic Metals. 103. 1960 (1999)

N. Tajima：“α-(BEDT-TTF)_2I_3 中高移动电子系统的异常磁输运”合成金属。103. 1960 (1999)

Y.Nishio: "Anomalous specific heat of (DMe-DCNQI-d_2 [1,1 ; 0] _<1-x>d_4 [2,2 ; 0] _x)_2Cu-system"Synthetic Metals. (in press).

Y.Nishio：“(DMe-DCNQI-d_2 [1,1 ; 0] _<1-x>d_4 [2,2 ; 0] _x)_2Cu-系统的异常比热”合成金属。

田嶋尚也: "Transport Properties of α-(BEDT-TTF)_2I_3 Under High Pressure-Ultra Narrow gap semiconductor"Synthetic Metals. (印刷中).

Naoya Tajima：“高压下 α-(BEDT-TTF)_2I_3 的输运特性 - 超窄带隙半导体”合成金属（正在出版）。