A Modified 8f Geometry with Reduced Optical Aberrations for Improved Time Domain Terahertz Spectroscopy

Laurita, N. J.; Cheng, Bing; Barkhouser, Robert H.; Neumann, V. A.; Armitage, N. P.

doi:10.1007/s10762-016-0281-x

Cited by 14 publications

(11 citation statements)

References 32 publications

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“…The orientation of the sample was such that the (1,1,0) direction was normal to the sample surface. Experiments were performed using a home built spectrometer with applied magnetic fields up to 7 T in Faraday geometry ( k THz H dc ) 49 . The polarization was such that the THz oscillatory fields e ac c and h ac (110) directions respectively.…”

Section: Methodsmentioning

confidence: 99%

Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

et al. 2017

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In this work, we present a comprehensive study of the low energy optical magnetic response of the skyrmionic Mott insulator Cu2OSeO3 via high resolution time-domain THz spectroscopy. In zero field, a new magnetic excitation (f0 = 2.03 THz) which has not been predicted by spin-wave theory is observed and shown, with accompanying time-of-flight neutron scattering experiments, to be a zone folded magnon from the R to Γ points of the Brillouin zone. Highly sensitive polarimetry experiments performed in weak magnetic fields, µ0H < 200 mT, observe Faraday and Kerr rotations which are proportional to the sample magnetization, allowing for optical detection of the skyrmion phase and construction of a magnetic phase diagram. From these measurements, we extract a critical exponent of β = 0.35 ± 0.04, in good agreement with the expected value for the 3D Heisenberg universality class of β = 0.367. In large magnetic fields, µ0H > 5 T, we observe the magnetically active uniform mode of the ferrimagnetic field polarized phase whose dynamics as a function of field and temperature are studied. In addition to extracting a g eff = 2.08 ± 0.03, we observe the uniform mode to decay through a non-Gilbert damping mechanism and to possesses a finite spontaneous decay rate, Γ0 ≈ 25 GHz, in the zero temperature limit. Our observations are attributed to Dzyaloshinkii-Moriya interactions, which have been proposed to be exceptionally strong in Cu2OSeO3 and are expected to impact the low energy magnetic response of such chiral magnets.

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Section: Methodsmentioning

confidence: 99%

Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

et al. 2017

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“…Then, epitaxial films were obtained by crystallizing the precursor layers by post-annealing in air at 1000 • C. The two films were found to be essentially identical with the only difference being slightly higher doping level in S2 that result in larger residual scattering, greater E F , and a smaller contribution to the dielectric constant from the QBT. The optical experiment was performed by using a home-built time-domain terahertz spectrometer (TDTS) which can typically access the frequency range between 150 GHz and 2 THz [29]. Further details can be found in Methods.…”

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confidence: 99%

Dielectric anomalies and interactions in the three-dimensional quadratic band touching Luttinger semimetal Pr2Ir2O7

et al. 2017

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Dirac and Weyl semimetals with linearly crossing bands are the focus of much recent interest in condensed matter physics. Although they host fascinating phenomena, their physics can be understood in terms of weakly interacting electrons. In contrast, more than 40 years ago, Abrikosov pointed out that quadratic band touchings are generically strongly interacting. We have performed terahertz spectroscopy on the films of the conducting pyrochlore Pr2Ir2O7, which has been shown to host a quadratic band touching. A dielectric constant as large as is observed at low temperatures. In such systems, the dielectric constant is a measure of the relative scale of interactions, which are therefore in our material almost two orders of magnitude larger than the kinetic energy. Despite this, the scattering rate exhibits a T 2 dependence, which shows that for finite doping a Fermi liquid state survives—however, with a scattering rate close to the maximal value allowed.

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“…Two samples with the orientations [-1,1,0] (d = 670 µm) and [0,0,1] (d = 590 µm) normal to the sample surface were measured in this study. TDTS transmission experiments were performed using a home-built spectrometer [30] in magnetic fields up to 6T in Faraday geometry ( k THz H dc ). Via a coupling of the THz fields to both electric and magnetic dipole transitions of the sample, TDTS accesses the sample's electromagnetic response with exceptional resolution from 0.2 -2 THz.…”

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confidence: 99%

Asymmetric Splitting of an Antiferromagnetic Resonance via Quartic Exchange Interactions in Multiferroic Hexagonal HoMnO3

Laurita

Luo

et al. 2017

Phys. Rev. Lett.

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The symmetric splitting of two spin-wave branches in an antiferromagnetic resonance (AFR) experiment has been an essential measurement of antiferromagnets for over half a century. In this work, circularly polarized time-domain THz spectroscopy experiments performed on the low symmetry multiferroic hexagonal HoMnO_{3} reveal an AFR of the Mn sublattice to split asymmetrically in an applied magnetic field, with an ≈50% difference in g factors between the high and low energy branches of this excitation. The temperature dependence of the g factors, including a drastic renormalization at the Ho spin ordering temperature, reveals this asymmetry to unambiguously stem from Ho-Mn interactions. Theoretical calculations demonstrate that the AFR asymmetry is not explained by conventional Ho-Mn exchange mechanisms alone and is only reproduced if quartic spin interactions are also included in the spin Hamiltonian. Our results provide a paradigm for the optical study of such novel interactions in hexagonal manganites and low symmetry antiferromagnets in general.

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A Modified 8f Geometry with Reduced Optical Aberrations for Improved Time Domain Terahertz Spectroscopy

Cited by 14 publications

References 32 publications

Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

Dielectric anomalies and interactions in the three-dimensional quadratic band touching Luttinger semimetal Pr2Ir2O7

Asymmetric Splitting of an Antiferromagnetic Resonance via Quartic Exchange Interactions in Multiferroic Hexagonal HoMnO3

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