Wide spectral range ultrafast pump–probe magneto-optical spectrometer at low temperature, high-magnetic and electric fields

Mertens, Fabian; Terschanski, Marc; Mönkebüscher, David; Ponzoni, Stefano; Bossini, Davide; Cinchetti, Mirko

doi:10.1063/5.0024449

Cited by 13 publications

(12 citation statements)

References 52 publications

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“…Theoretical calculations based on ab initio density functional theory have predicted anisotropic optical reflectivity in WTe 2 for an energy range 0.5 eV ≤ ω ≤ 3.5 eV as a function of the polarization [75]. Here, the experiments are carried out using a wide spectral range ultrafast pump-probe magneto-optical spectrometer at low-T/high-µ 0 H [76]. In particular, the probe beam of this set-up is sent through an additional element for the generation of supercontinuum pulses to perform reflectivity measurements.…”

Section: Static Optical Reflectivitymentioning

confidence: 99%

Positive Magnetoresistance and Chiral Anomaly in Exfoliated Type-II Weyl Semimetal Td-WTe2

Adhikari

Faina

et al. 2021

Nanomaterials

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Layered van der Waals semimetallic Td-WTe2, exhibiting intriguing properties which include non-saturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as a model topological type-II Weyl semimetal system. Here, ∼45 nm thick mechanically exfoliated flakes of Td-WTe2 are studied via atomic force microscopy, Raman spectroscopy, low-T/high-μ0H magnetotransport measurements and optical reflectivity. The contribution of anisotropy of the Fermi liquid state to the origin of the large positive transverse MR⊥ and the signature of chiral anomaly of the type-II Weyl Fermions are reported. The samples are found to be stable in air and no oxidation or degradation of the electronic properties is observed. A transverse MR⊥∼1200 % and an average carrier mobility of 5000 cm2V−1s−1 at T=5K for an applied perpendicular field μ0H⊥=7T are established. The system follows a Fermi liquid model for T≤50K and the anisotropy of the Fermi surface is concluded to be at the origin of the observed positive MR. Optical reflectivity measurements confirm the anisotropy of the electronic behaviour. The relative orientation of the crystal axes and of the applied electric and magnetic fields is proven to determine the observed chiral anomaly in the in-plane magnetotransport. The observed chiral anomaly in the WTe2 flakes is found to persist up to T=120K, a temperature at least four times higher than the ones reported to date.

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Section: Static Optical Reflectivitymentioning

confidence: 99%

Positive Magnetoresistance and Chiral Anomaly in Exfoliated Type-II Weyl Semimetal Td-WTe2

Adhikari

Faina

et al. 2021

Nanomaterials

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“…18,22,33 Instruments with higher sensitivities use much longer integration times 34 (several minutes) or use an OPA to only probe one wavelength at a time. 16 If a sample does induce transient changes to the polarisation state of the transmitted light, then S + = S − . Therefore, to recover the TA spectrum, ∆A T A (t), the average of the spectra measured in opposing fields is taken.…”

Section: Time-resolved Measurementsmentioning

confidence: 99%

A Femtosecond Magnetic Circular Dichroism Spectrometer

Sutcliffe,

Johansson

2021

Preprint

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We describe the development of a broadband magneto-optical spectrometer with femtosecond temporal resolution. The absorption spectrometer is based on a white-light supercontinuum (ca. 320 − 750 nm) using shot-to-shot temporal and spectral referencing at 1 kHz. Static and transient absorption spectra using circularly polarised light are collected in a magnetic field. The difference spectra with respect to the external field direction give the static and transient magneto-optical Faraday rotation (magnetic optical rotary dispersion) and ellipticity (magnetic circular dichroism) spectra. An achromatic quarter-wave plate is used and the impact of the deviation from ideal retardance on the spectra is discussed. Results from solution-based and thin-film samples are used to demonstrate the performance and wide applicability of the instrument. The sensitivities for the static and time-resolved data were found to be 5 and 0.4 mdeg, respectively. The method presents a simple way to measure magneto-optical spectra using a transient absorption spectrometer and an electromagnet.

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“…Theoretical calculations based on ab initio density functional theory have predicted anisotropic optical reflectivity in WTe 2 for an energy range 0.5 eV ≤ ω ≤ 3.5 eV as a function of the polarization [73]. Here, the experiments are carried out using a wide spectral range ultrafast pump-probe magnetooptical spectrometer at low-T /high-µ 0 H [74]. In particular, the probe beam of this set-up is sent through an additional element for the generation of supercontinuum pulses to perform reflectivity measurements.…”

Section: Static Optical Reflectivitymentioning

confidence: 99%

Positive magnetoresistance and chiral anomaly in exfoliated type-II Weyl semimetal $T_\mathrm{d}$-WTe$_{2}$

Adhikari¹,

Adhikari²,

Faina³

et al. 2021

Preprint

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Layered van der Waals semimetallic T d -WTe2, exhibiting intriguing properties which include nonsaturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as model topological type-II Weyl semimetal system. Here, ∼45 nm thick mechanically exfoliated flakes of T d -WTe2 are studied via atomic force microscopy, Raman spectroscopy, low-T /high-µ0H magnetotransport measurements and optical reflectivity. The contribution of anisotropy of the Fermi liquid state to the origin of the large positive transverse MR ⊥ and the signature of chiral anomaly of the type-II Weyl fermions are reported. The samples are found to be stable in air and no oxidation or degradation of the electronic properties are observed. A transverse MR ⊥ ∼1200 % and an average carrier mobility of 5000 cm 2 V −1 s −1 at T = 5 K for an applied perpendicular field µ0H ⊥ = 7 T are established. The system follows a Fermi liquid model for T ≤ 50 K and the anisotropy of the Fermi surface is concluded to be at the origin of the observed positive MR. The anisotropy of the electronic behaviour is also confirmed by optical reflectivity measurements. The relative orientation of the crystal axes and of the applied electric and magnetic fields is proven to give rise to the observed chiral anomaly in the in-plane magnetotransport.

show abstract

Wide spectral range ultrafast pump–probe magneto-optical spectrometer at low temperature, high-magnetic and electric fields

Cited by 13 publications

References 52 publications

Positive Magnetoresistance and Chiral Anomaly in Exfoliated Type-II Weyl Semimetal Td-WTe2

Positive Magnetoresistance and Chiral Anomaly in Exfoliated Type-II Weyl Semimetal Td-WTe2

A Femtosecond Magnetic Circular Dichroism Spectrometer

Positive magnetoresistance and chiral anomaly in exfoliated type-II Weyl semimetal $T_\mathrm{d}$-WTe$_{2}$

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