In: Physical Review B, 2021, vol. 103, no. 12, p. L121103
With infrared spectroscopy, we studied the bulk electronic properties of the topological antiferromagnet MnBi2Te4 with TN ≃ 25 K. With the support of band-structure calculations, we assign the intra- and interband excitations and determine the band gap of Eg ≈ 0.17 eV. We also obtain evidence for two types of conduction bands with light and very heavy carriers. The multiband free-carrier...
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In: Physical Review B, 2020, vol. 101, no. 22, p. 224515
The magnetic and superconducting properties of a series of underdoped Ba 1 − x Na x Fe 2 As 2 (BNFA) single crystals with 0.19 ≤ x ≤ 0.34 have been investigated with the complementary muon-spin-rotation ( μ SR ) and infrared spectroscopy techniques. The focus has been on the different antiferromagnetic states in the underdoped regime and their competition with superconductivity,...
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In: Proceedings of the National Academy of Sciences, 2020, vol. 117, no. 44, p. 27104–27110
We report the optical conductivity in high-quality crystals of the chiral topological semimetal CoSi, which hosts exotic quasiparticles known as multifold fermions. We find that the optical response is separated into several distinct regions as a function of frequency, each dominated by different types of quasiparticles. The low-frequency intraband response is captured by a narrow Drude peak...
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In: Nature Physics, 2020, p. -
Nd2Ir2O7 is a correlated semimetal with the pyrochlore structure, in which competing spin–orbit coupling and electron–electron interactions are believed to induce a time- reversal symmetry-broken Weyl semimetal phase characterized by pairs of topologically protected Dirac points at the Fermi energy1,2,3,4. However, the emergent properties in these materials are far from clear, and exotic...
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In: Nanoscale, 2020, vol. 12, no. 21, p. 11480–11488
Mid-infrared (MIR) represents a crucial spectral region for applications in spectroscopy, sensing, imaging, security and industry screening, owing to the strong characteristic vibrational transitions of many important molecules. However, the current MIR compatible materials are fragile, hazardous, and costly, which hampers the performance of MIR devices. Here, we developed a versatile...
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In: Physical Review B, 2020, vol. 101, no. 21, p. 214512
We studied the infrared response of polycrystalline samples of the iron arsenide superconductor (Rb,Cs)Ca2Fe4As4F2 (Rb,Cs-12442), which has a bilayer structure similar to the high-Tc cuprates YBa2Cu3O7 (YBCO) and Bi2Sr2CaCu2O8. The c-axis reflectivity spectra Rc have been derived from the reflectivity spectra of the polycrystalline samples Rpoly and the in-plane spectrum of a corresponding...
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In: Physical Review Research, 2020, vol. 2, no. 2, p. 023218
With terahertz and infrared spectroscopy we studied the in-plane response of an underdoped, twinned YBa2Cu3O6.6 single crystal with Tc=58(1)K in high magnetic fields up to B=30 Tesla (T) applied along the c axis. Our goal was to investigate the field-induced suppression of superconductivity and to observe the signatures of the three-dimensional (3D) incommensurate copper charge density wave...
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In: Journal of Physics: Condensed Matter, 2019, vol. 31, no. 40, p. 405701
We report magnetic susceptibility, resistivity and optical spectroscopy study on single crystal sample DySb. It exhibits extremely large magnetoresistance (XMR), and a magnetic phase transition from paramagnetic (PM) to antiferromagnetic (AFM) state at about 10 K. A 'screened' plasma edge at about 4000 cm−1 is revealed by optical measurement, which suggests that the material has a low...
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In: Physical Review Letters, 2019, vol. 122, no. 21, p. 217002
By means of infrared spectroscopy, we determine the temperature-doping phase diagram of the Fano effect for the in-plane Fe-As stretching mode in Ba1−xKxFe2As2. The Fano parameter 1=q2, which is a measure of the phonon coupling to the electronic particle-hole continuum, shows a remarkable sensitivity to the magnetic and structural orderings at low temperatures. Most strikingly, at elevated...
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In: Physical Review B, 2019, vol. 99, no. 12, p. 125119
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