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Among different topological and related phases of condensed matter, nodal semimetals occupy a special place—the electronic band topology in these materials is related to 3D bulk, rather than to surface, states. A great variety of different realizations of electronic band crossings (the nodes) leads to a plethora of different electronic properties, ranging from chiral anomaly to solid‐state realizations of a black‐hole horizon. The different nodal phases have similar low‐energy band structure and quasiparticle dynamics, which both can be accessed experimentally by a number of methods. Optical measurements with their large penetration depth and high energy resolution are ideally suited as such a bulk probe, especially at low energies where other spectroscopic methods often lack the required resolution. Herein, recent optical conductivity studies of different nodal semimetals are reviewed, possible limitations of such measurements are discussed, and a comparison between the experimental results, simple theoretical models, and band‐structure‐based calculations is provided. [ABSTRACT FROM AUTHOR]

We present a broadband optical-conductivity study of superconducting single-crystalline EuFe [ABSTRACT FROM AUTHOR]

We present a broadband optical-conductivity study of superconducting single-crystalline EuFe [ABSTRACT FROM AUTHOR]

Accurate determination of the intrinsic electronic structure of thermoelectric materials is a prerequisite for utilizing an electronic band engineering strategy to improve their thermoelectric performance. Herein, with high‐resolution angle‐resolved photoemission spectroscopy (ARPES), the intrinsic electronic structure of the 3D half‐Heusler thermoelectric material ZrNiSn is revealed. An unexpectedly large intrinsic bandgap is directly observed by ARPES and is further confirmed by electrical and optical measurements and first‐principles calculations. Moreover, a large anisotropic conduction band with an anisotropic factor of 6 is identified by ARPES and attributed to be one of the most important reasons leading to the high thermoelectric performance of ZrNiSn. These successful findings rely on the grown high‐quality single crystals, which have fewer Ni interstitial defects and negligible in‐gap states on the electronic structure. This work demonstrates a realistic paradigm to investigate the electronic structure of 3D solid materials by using ARPES and provides new insights into the intrinsic electronic structure of the half‐Heusler system benefiting further optimization of thermoelectric performance. [ABSTRACT FROM AUTHOR]