2024/11/14(Thu) 15:00 -16:30 五樓第一會議室 5F, 1st Meeting Room
Title
Unconventional electronic ground states in single - and infinite -layer Ruddlesden - Popper iridates
Speaker
徐有德助理教授 (國立清華大學物理系) Assistant Prof. Yu-Te Hsu (Department of Physics, National Tsing Hua University)Abstract
Iridium oxides (iridates) present a promising platform to investigate the interplay between electron-electron and spin-orbit interactions, thanks to its comparable energy scales of spin-orbit coupling, Coulomb repulsion and electronic bandwidth [1]. The Ruddlesden-Popper iridate series Srn+1IrnO3n+1 represents a particularly interesting materials family, in which the strength of electron correlations and dimensionality can be tuned via varying layer number n and a versatile electronic ground states can be realized therein. For example, the single-layer compound Sr2IrO4 (n = 1) is a spin-orbit-assisted antiferromagnetic Mott insulator [2] whereas the infinite-layer compound SrIrO3 (n = ∞) is a topological semimetal with lattice-symmetry-protected Dirac points. In this talk, I will discuss the evolution of low-temperature electronic ground states in electron-doped Sr2IrO4 [3] and the discovery of Fermi surface in SrIrO3 by means of quantum oscillations [4]. In electron-doped Sr2-xLaxIrO4, we find that the effective carrier number undergoes a dramatic increase across a critical doping level xc ≈ 0.16, at which the quasiparticle effective mass shows a pronounced enhancement. These characteristics closely resembles the pseudogap phenomenology in superconducting cuprates, yet no superconductivity has so far been realized in the iridates, suggesting the pseudogap is a common feature of doped quasi-2D Mott insulators and not linked to the emergence of superconductivity. In SrIrO3, we have mapped out its Fermi surface using quantum oscillation measurement, and find it to be consistent with bandstructure calculations with robust Dirac crossings near the Fermi level, albeit the quasiparticle effective mass is substantially enhanced and indicative of strong correlations in this topological semimetal. Interestingly, a T-linear, strange-metallic component to its low-temperature resistivity, hinting at the possibility of a coexistence between a Fermi-liquid and strange metallic sector in its electronic ground states.
Reference
[1] Rau et al, Annu. Rev. Condens. Matter Phys. 7:195-221 (2016)
[2] Kim et al., Science 345, 187-190 (2014)
[3] Hsu et al., Nature Physics 20, 1596-1602 (2024)
[4] Hsu et al., npj Quantum Materials 6:92 (2021)
CV
Language
演講語言 (Language): in English
Hosted by