Ryosuke Oka: Crystallization of heavy fermions via epitaxial strain in spinal LiV2O4 thin film

Date: Wednesday, June 4th, 2025

Location: Elings Hall, room 1601

Time: 12:30 pm - 1:30 pm

Crystallization of heavy fermions via epitaxial strain in spinel LiV2O4 thin film 

​​​​​Abstract: The mixed-valent V3.5+ spinel oxide LiV2O4 is well known as the first 3d-electron system exhibiting heavy fermion (HF) behavior [1, 2]. At low temperatures, it displays all hallmarks of HF systems, including a large Sommerfeld coefficient γ of the specific heat reaching 420 mJ/mol·K2 and metallic behavior with Fermiliquid properties below 2 K. However, the origin of the HF behavior in the absence of localized f-electrons has been a decades-old puzzle. One of the key pieces for the puzzle may lie in a difference between LiV2O4 and f- electron HF systems, the emergence of a charge-ordered (CO) phase under hydrostatic pressure [3]. To further investigate phases proximate 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 multiple phases in these films. I will also introduce our preliminary comprehensive low-temperature transport measurements on a single crystal using a dilution refrigerator, which are the first measurements directly probing the heavy quasiparticles at very low temperatures [5]. Finally, I will propose our own “charge frustration" scenario for the HF formation based on these findings.

Bio: Max Planck Institute for Solid State Research, Stuttgart, Germany Department of Physics, The University of Tokyo, Tokyo, Japan