Transient Drude Response Dominates Near-Infrared Pump–Probe Reflectivity in Nodal-Line Semimetals ZrSiS and ZrSiSe

Abstract

The ultrafast optical response of two nodal-line semimetals, ZrSiS and ZrSiSe, was studied in the near-infrared using transient reflectivity. The two materials exhibit similar responses, characterized by two features, well resolved in time and energy. The first transient feature decays after a few hundred femtoseconds, while the second lasts for nanoseconds. Using Drude-Lorentz fits of the materials' equilibrium reflectance, we show that the fast response is well-represented by a decrease of the Drude plasma 1 arXiv:2005.04248v1 [cond-mat.mtrl-sci] 8 May 2020 frequency, and the second feature by an increase of the Drude scattering rate. This directly connects the transient data to a physical picture in which carriers, after being excited away from the Fermi energy, return to that vicinity within a few hundred femtoseconds by sharing their excess energy with the phonon bath, resulting in a hot lattice that relaxes only through slow diffusion processes (ns). The emerging picture reveals that the sudden change of the density of carriers at the Fermi level instantaneously modifies the transport properties of the materials on a timescale not compatible with electron phonon thermalization and is largely driven by the reduced density of states at the nodal line.

Obvious Surface States Connecting to the Projected Triple Points in NaCl’s Phonon Dispersion

“…One finds the points at a1, a2, a3 a4 are all with a quadratic band splitting, however, for the points b1, b2, b3, b4, they are with a classic linear band splitting. Hence, the doubly degenerate band along the X- , is composed of doubly degenerate points with linear band splitting, forming a linear nodal line ( Zhou et al, 2018b ; Chen et al, 2018 ; Chang et al, 2019 ; Yan et al, 2019 ; Li et al, 2020a ; Kirby et al, 2020 ; Meng et al, 2020 ; Wang and Yang, 2021 ). The doubly degenerate band along the , is composed of doubly degenerate points with quadratic band splitting, forming a quadratic nodal line ( Yu et al, 2019 ; Wang et al, 2020c ).…”

Chemical bonds in topological materials

“…As a result, many square-net materials are TSMs, or in the presence of strong SOC, can be weak TIs [28]. Several of such materials have been shown to have remarkable properties, ranging from exotic electronic transport, to the promise for applications in optical devices, to experimental verification of novel surface states [16,53,[65][66][67][68][69][70][71][72][73][74][75][76].…”

Realization of Opened and Closed Nodal Lines and Four- and Three-fold Degenerate Nodal Points in XPt (X = Sc, Y, La) Intermetallic Compound: A Computational Modeling Study

“…Topological semimetals/metals can be roughly classified into three main parts: nodal-point (Chen et al, 2015;Yuan et al, 2017;Zhang et al, 2017aZhang et al, ,c, 2018cJing and Heine, 2018;Ma et al, 2018;Tsipas et al, 2018;Khoury et al, 2019), nodal-line (Chang et al, 2016;Liu et al, 2018b;Guo et al, 2019;Sankar et al, 2019;Tang et al, 2019;Xu et al, 2019;Zhang et al, 2019;Jin et al, 2020a;Kirby et al, 2020;Zhou et al, 2020), and nodal-surface (Türker and Sergej, 2018;Wu et al, 2018;Zhang et al, 2018b,d;Fu et al, 2019;Yang et al, 2019bChen et al, 2020;Wang et al, 2020e;Xiao et al, 2020) semimetals/metals enjoying zero-, one-, and two-dimensional topological elements, respectively. The main examples of nodal-point semimetals/metals are Weyl and Dirac semimetals/metals with 2-and 4-fold degenerate band-crossing points with linear dispersion.…”