Who
Dr. Ryosuke Oka, Max Planck Institute for Solid State Research / Tokyo U.
Abstract
The mixed-valent V3.5+ spinel oxide LiV2O4 is well known as the first 3d-electron system to exhibit heavy fermion (HF) behavior [1, 2]. At low temperatures, it shows all the hallmarks of HF systems, including a large Sommerfeld coefficient γ of the specific heat reaching 420 mJ/mol·K2 , and metallic behavior with Fermi-liquid properties below 2 K. However, the origin of this HF behavior in the absence of localized f-electrons has remained a long-standing puzzle.
One key to this puzzle may be the emergence of a charge-ordered phase under hydrostatic pressure [3], which distinguishes LiV2O4 from conventional f-electron HF systems. To further explore the phases proxi- mate to the HF state, we applied various types of anisotropic strain via thin-film heteroepitaxy using four different substrates [4]. In this talk, I will present our thin-film results and highlight the emergence of mul- tiple phases. I will also introduce our preliminary comprehensive low-temperature transport measurements on a single crystal using a dilution refrigerator—the first measurements that directly probe well-defined heavy quasiparticles at very low temperatures [5]. Based on these findings, I will propose a new “charge frustration” scenario for the formation of the HF state.
References
[1] S. Kondo et al., Phys. Rev. Lett. 78, 3729 (1997).
[2] C. Urano et al., Phys. Rev. Lett. 85, 1052 (2000).
[3] K. Takeda et al., Physica B 359, 1312 (2005).
[4] U. Niemann, Y.-M. Wu, R. Oka et al., Proc. Natl. Acad. Sci. USA 120, e2215722120 (2023).
[5] R. Oka et al., in preparation
One key to this puzzle may be the emergence of a charge-ordered phase under hydrostatic pressure [3], which distinguishes LiV2O4 from conventional f-electron HF systems. To further explore the phases proxi- mate to the HF state, we applied various types of anisotropic strain via thin-film heteroepitaxy using four different substrates [4]. In this talk, I will present our thin-film results and highlight the emergence of mul- tiple phases. I will also introduce our preliminary comprehensive low-temperature transport measurements on a single crystal using a dilution refrigerator—the first measurements that directly probe well-defined heavy quasiparticles at very low temperatures [5]. Based on these findings, I will propose a new “charge frustration” scenario for the formation of the HF state.
References
[1] S. Kondo et al., Phys. Rev. Lett. 78, 3729 (1997).
[2] C. Urano et al., Phys. Rev. Lett. 85, 1052 (2000).
[3] K. Takeda et al., Physica B 359, 1312 (2005).
[4] U. Niemann, Y.-M. Wu, R. Oka et al., Proc. Natl. Acad. Sci. USA 120, e2215722120 (2023).
[5] R. Oka et al., in preparation