Pressure-induced insulator-metal transition in transition metal chalcogenides studied by nuclear resonant inelastic scattering

通过核共振非弹性散射研究过渡金属硫属化物中压力诱导的绝缘体-金属转变

• 批准号: 15540319
• 负责人: KOBAYASHI Hisao
• 金额: $ 2.37万
• 依托单位: University of Hyogo (2004)Himeji Institute of Technology (2003)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540319/
• 关键词: High Pressure; Phonon; Insulator-metal transition; Nuclear resonant inelastic scattering; 電荷圧縮率

Iron sulfide, FeS, has been attracting attention in geosciences as well as condensed matter physics. Although the pressure vs.temperature phase diagram has been contradictory, FeS undergoes two successive first-order phase transitions at room temperature, from the troilite to an MnP-type structure at 3.5 GPa and then to a monoclinic structure at 6.5 GPa. At ambient conditions, FeS is an antiferromagnetic semiconductor, where an electron correlation plays an important role. Electrical resistivity measurements of FeS under pressure show that the semiconductor-metal and metal-semiconductor transitions occur at 3.5 and 6.5 GPa, respectively, corresponding to the structural phase transitions at room temperature. These phase transitions cause simultaneous changes in the electronic and structural properties. Therefore, we need to investigate the phonon properties of FeS in each phase and around these phase transitions from the condensed matter physical points of view.In this research, we have applied the nuclear resonant inelastic x-ray scattering to extract the partial phonon DOS of FeS under pressure and then calculated the total phonon DOS. It is found that the phonon DOS of FeS is modified by the pressure-induced phase transitions.We derive the pressure dependence of thermodynamic parameters from these phonon DOS. In these thermodynamic parameters, the pressure dependence of a force constant is determined by the Hund's rules of Fe^<2+> ion in FeS. A comparison of the observed and estimated compressibilities makes it clear that there is large pure electronic contribution in the observed compressibility in the metallic state. Consequently the larger observed compressibility in the metallic state is provided by a purely electronic contribution, which is estimated to be about 40% of the observed compressibility. Therefore, this discontinuous change of purely electronic contribution characterizes the phase transition at 3.5 GPa.

硫化铁（FeS）在地球科学和凝聚态物理中一直受到人们的关注。虽然压力与温度的相图一直是矛盾的，FeS在室温下经历了两个连续的一级相变，在3.5 GPa下从陨硫铁到MnP型结构，然后在6.5 GPa下到单斜结构。在环境条件下，FeS是一种反铁磁半导体，其中电子相关起着重要作用。压力下的FeS的电阻率测量表明，超导体-金属和金属-半导体的转变分别发生在3.5和6.5 GPa，对应于在室温下的结构相变。这些相变引起电子和结构性质的同时变化。因此，我们需要从凝聚态物理的角度来研究FeS在各个相态以及相变前后的声子性质。本研究利用核共振非弹性X射线散射方法提取了压力作用下FeS的部分声子态密度，进而计算了总声子态密度。结果表明，压力诱导相变对FeS的声子态密度有一定的影响，并由此导出了热力学参数与压力的关系。在这些热力学参数中，力常数的压力依赖性由FeS中Fe^<2+>离子的Hund规则确定。通过对所观测到的压缩系数和估算的压缩系数的比较，可以清楚地看出，在金属态下所观测到的压缩系数中有很大的纯电子贡献。因此，在金属状态下观察到的更大的压缩性是由纯电子贡献提供的，估计约为观察到的压缩性的40%。因此，这种纯电子贡献的不连续变化表征了3.5 GPa下的相变。

项目成果

Structural and electrical properties of stoichiometric FeS compounds under high pressure at low temperature

化学计量FeS化合物在高压低温下的结构和电学性质

• 发表时间: 2005
• 期刊: Phys.Rev.B 71
• 作者: K.Chong;T.Hirai;T.Kawai;S.Hashimoto;N.Ohno;H.Kobayashi
• 通讯作者: H.Kobayashi

Phonon density of states and compression behavior in iron sulfide under pressure

硫化铁在压力下的声子态密度和压缩行为

• 发表时间: 2004
• 期刊: Phys.Rev.Lett. 93
• 作者: K.Chong;T.Hirai;T.Kawai;S.Hashimoto;N.Ohno;H.Kobayashi;H.Kobayashi;H.Kobayashi;H.Kobayashi et al.;H.Kobayashi et al.;H.Kobayashi
• 通讯作者: H.Kobayashi

Charge ordering in Eu_4As_3 under pressure

压力下 Eu_4As_3 中的电荷排序

• 发表时间: 2005
• 期刊: J.Phys.: Condens.Matter. 17
• 作者: K.Chong;T.Hirai;T.Kawai;S.Hashimoto;N.Ohno;H.Kobayashi;H.Kobayashi
• 通讯作者: H.Kobayashi

H.Kobayashi et al.: "Magnetism and deHaas-Van Alphen effect in NiSb"J.Mag.Mag.Mater. (印刷中).

H. Kobayashi 等人：“NiSb 中的磁性和 deHaas-Van Alphen 效应”J.Mag.Mag.Mater。

Magnetism and de Haas–Van Alphen effect in NiSb

• DOI: 10.1016/j.jmmm.2003.11.172
• 发表时间: 2004-05
• 期刊: Journal of Magnetism and Magnetic Materials
• 影响因子: 2.7
• 作者: H. Kobayashi;M. Kageshima;N. Kimura;H. Aoki;Masafumi Oohigashi;K. Motizuki;T. Kamimura