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Selective observation of spin and charge dynamics in an organic superconductor lambda-(BETS)(2)GaCl4 using Ga-69,Ga-71 NMR measurements

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Title: Selective observation of spin and charge dynamics in an organic superconductor lambda-(BETS)(2)GaCl4 using Ga-69,Ga-71 NMR measurements
Authors: Kobayashi, T. Browse this author
Tsuji, K. Browse this author
Ohnuma, A. Browse this author
Kawamoto, A. Browse this author →KAKEN DB
Issue Date: 15-Dec-2020
Publisher: American Physical Society (APS)
Journal Title: Physical Review B
Volume: 102
Issue: 23
Start Page: 235131
Publisher DOI: 10.1103/PhysRevB.102.235131
Abstract: For the unconventional organic superconductor lambda-(BETS)(2)GaCl4 [BETS = bis(ethylenedithio) tetraselenafulvalene], the importance of both spin and charge degrees of freedom has been discussed based on the broadening of the NMR linewidth due to charge disproportionation and the occurrence of a spin-density-wave phase near the superconducting phase. NMR with the nuclear spin of 1/2, previously used for studying organic conductors, is an effective method for revealing electronic states microscopically; however, it cannot distinguish between charge and spin anomalies. To resolve this problem, in this paper, we performed Ga-69,Ga-71-NMR measurements, which enabled us to study both charge and spin dynamics using different gyromagnetic ratios and quadrupole moments between two isotopes. The spin-lattice relaxation rate is dominated by electric-field gradient fluctuations originating from molecular dynamics above 150 K and, below this temperature, it is dominated by spin fluctuations derived from the pi electrons of BETS layers. This change in the relaxation mechanism is considered to be due to the development of interactions between GaCl4 ions and BETS layers upon freezing of the molecular motion by cooling. Below 150 K, the contribution of spin fluctuations monotonically increases, and no increase in the charge fluctuation was observed, suggesting that the spin degree of freedom plays a major role in low-temperature physical properties. Our findings will aid theoretical studies on superconducting properties.
Rights: ©2020 American Physical Society
Type: article
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 河本 充司

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