Title: Electrodynamics of hidden quasiparticles and plasmons in nodal-metals
Speaker: Yinming Shao (邵垠铭), Columbia University
Time: 4 pm, Jul 4th (Tuesday), 2023
Location: 理科楼C302
Abstract: The discovery of nodal-line semimetal ZrSiS extends the notion of Dirac fermions from points to lines and loops in the momentum space [1]. Identifying new nodal-line fermions is challenging since often the Dirac nodal-lines are dispersive, submerged within a Fermi sea, and gapped by spin-orbit-coupling. I will first introduce how precise power-law behavior of the optical response function can reveal the hidden nodal-line fermions, using NbAs2 as an example [2]. The large anisotropy associated with nodal-line structure gives rise to greatly reduced kinetic energy along the line. I will discuss the two fundamental spectroscopic hallmarks of electronic correlations observed in ZrSiSe [3]: strong reduction (1/3) of the free carrier Drude weight and of the Fermi velocity renormalization compared to predictions of density functional theory. Another consequence of the nodal-line structure is the large difference in the plasma frequencies for in-plane and out-of-plane responses, leading to a broadband hyperbolic regime covering infrared and visible frequencies. I will show our recent observation of propagating hyperbolic waves in ZrSiSe, enabled by the van Hove singularities in the nodal-squares [4]. Finally, I will discuss our recent effort in isolating surface and bulk electrodynamics in Weyl semimetals based on near-field photocurrent imaging at the nanoscale [5]. Our tip-based approach circumvents the diffraction limit and surface- and bulk-related nonlinear contributions are distinguished through their “symmetry fingerprints” in the real-space nano-photocurrent maps.
Refs:
[1] L. M. Schoop et al, Nat. Commun. 7, 11696 (2016)
[2] Y. Shao, Z. Sun et al, PNAS 116, 1168 (2019)
[3] Y. Shao et al, Nat. Phys. 16, 6 (2020)
[4] Y. Shao et al, “Infrared Plasmons Propagate through a Hyperbolic Nodal Metal”, Sci. Adv. 8, eadd6169 (2022).
[5] Y. Shao et al, PNAS 118, (48) e2116366118 (2021).
BIO: 邵垠铭博士于2009-2013本科就读于浙江大学。先后于加州大学圣地亚哥分校（2013-2016）和哥伦比亚大学（2017-2019）攻读物理学博士学位。2020至今于哥伦比亚大学从事博士后研究。
