TY - JOUR
T1 - Involvement of structural dynamics in charge-glass formation in strongly frustrated molecular metals
AU - Thomas, Tatjana
AU - Saito, Yohei
AU - Agarmani, Yassine
AU - Thyzel, Tim
AU - Lonsky, Martin
AU - Hashimoto, Kenichiro
AU - Sasaki, Takahiko
AU - Lang, Michael
AU - Müller, Jens
N1 - Funding Information:
We acknowledge support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through TRR 288 - 422213477 (Projects A06 and B02). This work was also supported by Grants-in-Aid for Scientific Research (KAKENHI) from MEXT, Japan (Grants No. JP21H01793, No. JP20H05144, No. JP19H01833, and No. JP18KK0375), and Grant-in-Aid for Scientific Research for Transformative Research Areas (A) Condensed Conjugation (Grants No. JP20H05869 and No. JP21H05471) from Japan Society for the Promotion of Science (JSPS). Y.S. and M.L. acknowledge technical assistance by S. Hartmann.
Publisher Copyright:
© 2022 American Physical Society.
PY - 2022/1/15
Y1 - 2022/1/15
N2 - We present a combined study of thermal expansion and resistance fluctuation spectroscopy measurements exploring the static and dynamic aspects of the charge-glass formation in the quasi-two-dimensional organic conductors θ-(BEDT-TTF)2MM′(SCN)4 with M = Cs and M′ = Co,Zn. In these materials, the emergence of a novel charge-glass state so far has been interpreted in purely electronic terms by considering the strong frustration of the Coulomb interactions on a triangular lattice. Contrary to this view, we provide comprehensive evidence for the involvement of a structural glasslike transition at Tg∼90-100K. This glassy transition can be assigned to the freezing of structural conformations of the ethylene endgroups in the donor molecule with an activation energy of Ea≈0.32eV, and the concomitant slowing down of the charge-carrier dynamics is well described by a model of nonexponential kinetics. These findings disclose an important aspect of the phase diagram and calls for revisiting the present views of the glassy dynamics in the whole family of θ-(BEDT-TTF)2MM′(SCN)4. Our results suggest that the entanglement of slow structural and charge-cluster dynamics due to the intimate coupling of lattice and electronic degrees of freedom determine the charge-glass formation under geometric frustration.
AB - We present a combined study of thermal expansion and resistance fluctuation spectroscopy measurements exploring the static and dynamic aspects of the charge-glass formation in the quasi-two-dimensional organic conductors θ-(BEDT-TTF)2MM′(SCN)4 with M = Cs and M′ = Co,Zn. In these materials, the emergence of a novel charge-glass state so far has been interpreted in purely electronic terms by considering the strong frustration of the Coulomb interactions on a triangular lattice. Contrary to this view, we provide comprehensive evidence for the involvement of a structural glasslike transition at Tg∼90-100K. This glassy transition can be assigned to the freezing of structural conformations of the ethylene endgroups in the donor molecule with an activation energy of Ea≈0.32eV, and the concomitant slowing down of the charge-carrier dynamics is well described by a model of nonexponential kinetics. These findings disclose an important aspect of the phase diagram and calls for revisiting the present views of the glassy dynamics in the whole family of θ-(BEDT-TTF)2MM′(SCN)4. Our results suggest that the entanglement of slow structural and charge-cluster dynamics due to the intimate coupling of lattice and electronic degrees of freedom determine the charge-glass formation under geometric frustration.
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U2 - 10.1103/PhysRevB.105.L041114
DO - 10.1103/PhysRevB.105.L041114
M3 - Article
AN - SCOPUS:85124134086
SN - 2469-9950
VL - 105
JO - Physical Review B
JF - Physical Review B
IS - 4
M1 - L041114
ER -