INVESTIGATIONS OF THE ANISOTROPIC SEMICONDIUCTING GAP IN THE HEVY-FERMION COMPOUNDS

重费米子化合物中各向异性半导体能隙的研究

• 批准号: 08640460
• 负责人: EKINO Toshikazu
• 金额: $ 1.41万
• 依托单位: HIROSHIMA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08640460/
• 关键词: ELECTRON TUNNELING; ENERGY GAP; KONDO SEMICONDUCTOR; Ce_3Bi_4Pt_3; YbB_1; 磁場効果

Measurements of the energy gap in the Ce- and Yb- based Kondo semiconductors have been carried for the first time using break junctions. Since this technique provides the cleanest interface, it is possible to investigate the intrinsic features of this compound with very reactive surface properties. For Ce<@D23@>D2Bi<@D24@>D2Pt<@D23@>D2, the features of clear gap-edge peaks and low zero-bias leakage in dI (V) /dV resemble those of the superconducting tunneling density of states, although the mechanism of gap formation is completely different to each other. The gap magnitudes of 2DELTA (]SY.apprxeq.[) 90 meV at 4.2 K defined by the peak-to-peak separation in dI (V) /dV are much larger than the activation energy obtained from p (T) for the identical sample, but are roughly the same magnitude as that obtained from the infrared measurements. The ratio 2DELTA /k<@D2B@>D2T<@D2x@>D2 = 13 (]SY.+-。[) 2 is evaluated using T<@D2x@>D2 = 80 K,where T<@D2x@>D2 is the temperature at which the suscepti … More bility exhibits a broad maximum. This ratio agrees well with that of CeRhSb and CeNiSn, in which the gaps open below T<@D2x@>D2. These results demonstrate that the gap formation is directly connected with T<@D2x@>D2 in these Ce-based Kondo semiconductors. For YbB<@D212@>D2, very sharp gap-edge structures with quite low leakage of the zero-bias conductance are commonly observed in every junction at 4.2 K,from which the average gap value of 2DELTA (]SY.apprxeq.[) 230 meV is obtained. This is unexpectedly larger than the gap of (]SY.apprxeq.[) 12 meV from the transport measurements. Upon warming, this giant gap of (]SY.apprxeq.[) 3000 K reduces to disappear at 60 - 90 K,which is close to the T<@D2x@>D2. of this comound. This feature is similar to that of Ce-based Kondo-semiconductors. However, the ratio 2DELTA/k<@D2B@>D2T<@D2x@>D2 (]SY.apprxeq.[) 37 of YbB<@D212@>D2 is (]SY.apprxeq.[) 3 times larger than that of the cubic Ce<@D23@>D2Bi<@D24@>D2Pt<@D23@>D2 compound having almost the same T<@D2x@>D2 value, thereby indicating that the characteristic energy for the gap creation in ybB<@D212@>D2 is larger than that in Ce<@D23@>D2Bi<@D24@>D2Pt<@D23@>D2. Further, by examining the susceptibility data of YbB<@D212@>D2 and Ce<@D23@>D2Bi<@D24@>D2Pt<@D23@>D2, we find the scaling temperatures T<@D1**@>D1 for each compound, which make the ratio 2DELTA/k<@D2B@>D2T<@D1**@>D1 a common value of (]SY.apprxeq.[) 3 - 4. Less

在基于Ce和Yb的Kondo半导体中，能量间隙的测量首次使用断结进行。由于这种技术提供了最干净的界面，因此有可能研究这种具有非常活性表面性质的化合物的内在特征。对于Ce<@D23@>D2Bi<@D24@>D2Pt<@D23@>D2, dI (V) /dV中清晰的隙边峰和低零偏漏的特征与超导隧穿态密度相似，尽管两者的隙形成机制完全不同。2DELTA (]SY.apprxeq.；[)在4.2 K下，由dI (V) /dV的峰对峰分离定义的90 meV比由p (T)得到的相同样品的活化能大得多，但与红外测量得到的活化能大致相同。比2δ/ k < @D2B@ > D2T < @D2x@ > D2 = 13 (SY。+ -。[) 2用T<@D2x@>D2 = 80 K来计算，其中T<@D2x@>D2是磁化率达到最大值时的温度。这一比值与CeRhSb和CeNiSn相吻合，两者的间隙在T<@D2x@>D2以下打开。这些结果表明，在这些ce基Kondo半导体中，间隙的形成与T<@D2x@>D2直接相关。对于YbB<@D212@>D2，在4.2 K时，在每个结处通常观察到非常尖锐的隙边结构，其零偏导漏极低，由此平均隙值为2DELTA (]SY.apprxeq。[)得到230 meV。这出乎意料地大于[]y .apprxeq的差距。[) 12 meV输运测量值。一旦变暖，这个巨大的缺口就会出现。[) 3000 K在60 ~ 90 K时逐渐消失，接近于T<@D2x@>D2。这个化合物的。这一特性与基于ce的kondo半导体相似。然而，比值2DELTA/k<@D2B@>D2T<@D2x@>D2 (]SY.apprxeq。[) 37的YbB<@D212@>D2是(]y .apprxeq。[)比具有几乎相同T<@D2x@>D2值的立方化合物Ce<@D23@>D2Bi<@D24@>D2Pt<@D23@>D2大3倍，从而表明ybB<@D212@>D2比Ce<@D23@>D2Bi<@D24@>D2Pt<@D23@>D2大。此外，通过对YbB<@ d212 @>D2和Ce<@ d23 @>D2Bi<@ d24 @>D2Pt<@ d23 @>D2的敏感性数据的分析，我们发现每种化合物的结垢温度T<@D1**@>D1，使得2DELTA/k<@ d2b @>D2T<@D1**@>D1的比值为(]SY.apprxeq。[] 3 - 4。少

项目成果

T.EKINO, T.Takabatake, H,Fujii: "Brealc-Junction measurements of CeNiSn under magnefic fields" Physica B. 230-232. 635-637 (1997)

T.EKINO、T.Takabatake、H、Fujii：“磁场下 CeNiSn 的 Brealc 结测量”Physica B. 230-232。

Y.Janssen, H,Fujii, T.EKINO, K.Izawa, T.Suzuki, I.Fujita, FRdcBoir: "Giant magnetoresis lance in Ce_2Fe_<17>" Physical Review B. 56. 13716-13719 (1997)

Y.Janssen、H、Fujii、TEKINO、K.Izawa、T.Suzuki、I.Fujita、FRdcBoir：“Ce_2Fe_<17> 中的巨磁气枪”物理评论 B. 56. 13716-13719 (1997)

Y.Janssen, H.Fujii, T.EKINO, K.Izawa, T.Suzuki, I.Fujita: "Giant magneto resistance in Ce_2Fe_<17>" Physical Review B. 56. 13716-13719 (1997)

Y.Janssen、H.Fujii、TEKINO、K.Izawa、T.Suzuki、I.Fujita：“Ce_2Fe_<17> 中的巨磁阻”物理评论 B. 56. 13716-13719 (1997)

T.EKINO, H.Umeda, K.Katoh, T.Takabatake, H.Fujii: "Tunneling Spectroscopy of the Kondo Semiconductor Ce_3Bい_4Pt_3" Journal of Magnetism and Magnetic Materials. 177-181(印刷中). 2 (1998)

T.EKINO、H.Umeda、K.Katoh、T.Takabatake、H.Fujii：“近藤半导体 Ce_3B_4Pt_3 的隧道光谱”《磁性与磁性材料杂志》177-181（出版中）。

R.A.Goschke, K.Gloos, C.Geibel, , T.Ekino, and F.Steglich: "Vacuum-tunneling spectroscopy of heavy -fermion compounds using alow-temperature tunnelling microscope" Czech.J.Phys.46, Suppl.S2. 797-798 (1996)

R.A.Goschke、K.Gloos、C.Geibel、T.Ekino 和 F.Steglich：“使用低温隧道显微镜对重费米子化合物进行真空隧道光谱分析”Czech.J.Phys.46，增刊 S2。