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Carey B, Wessling NK, Steeger P, Schmidt R, Michaelis de Vasconcellos S, Bratschitsch R, Arora A. Giant Faraday rotation in atomically thin semiconductors. Nat Commun 2024; 15:3082. [PMID: 38600090 PMCID: PMC11006678 DOI: 10.1038/s41467-024-47294-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 03/21/2024] [Indexed: 04/12/2024] Open
Abstract
Faraday rotation is a fundamental effect in the magneto-optical response of solids, liquids and gases. Materials with a large Verdet constant find applications in optical modulators, sensors and non-reciprocal devices, such as optical isolators. Here, we demonstrate that the plane of polarization of light exhibits a giant Faraday rotation of several degrees around the A exciton transition in hBN-encapsulated monolayers of WSe2 and MoSe2 under moderate magnetic fields. This results in the highest known Verdet constant of -1.9 × 107 deg T-1 cm-1 for any material in the visible regime. Additionally, interlayer excitons in hBN-encapsulated bilayer MoS2 exhibit a large Verdet constant (VIL ≈ +2 × 105 deg T-1 cm-2) of opposite sign compared to A excitons in monolayers. The giant Faraday rotation is due to the giant oscillator strength and high g-factor of the excitons in atomically thin semiconducting transition metal dichalcogenides. We deduce the complete in-plane complex dielectric tensor of hBN-encapsulated WSe2 and MoSe2 monolayers, which is vital for the prediction of Kerr, Faraday and magneto-circular dichroism spectra of 2D heterostructures. Our results pose a crucial advance in the potential usage of two-dimensional materials in ultrathin optical polarization devices.
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Affiliation(s)
- Benjamin Carey
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Strasse 10, Münster, Germany
- School of Mathematics and Physics, The University of Queensland, St Lucia, QLD, Australia
| | - Nils Kolja Wessling
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Strasse 10, Münster, Germany
- Institute of Photonics, Department of Physics, University of Strathclyde, 99 George Street, Glasgow, UK
| | - Paul Steeger
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Strasse 10, Münster, Germany
| | - Robert Schmidt
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Strasse 10, Münster, Germany
| | | | - Rudolf Bratschitsch
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Strasse 10, Münster, Germany.
| | - Ashish Arora
- Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Strasse 10, Münster, Germany.
- Department of Physics, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune, Maharashtra, India.
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Carey B, Wessling NK, Steeger P, Klusmann C, Schneider R, Fix M, Schmidt R, Albrecht M, Michaelis de Vasconcellos S, Bratschitsch R, Arora A. High-Performance Broadband Faraday Rotation Spectroscopy of 2D Materials and Thin Magnetic Films. SMALL METHODS 2022; 6:e2200885. [PMID: 36228108 DOI: 10.1002/smtd.202200885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 09/21/2022] [Indexed: 06/16/2023]
Abstract
A Faraday rotation spectroscopy (FRS) technique is presented for measurements on the micrometer scale. Spectral acquisition speeds of about two orders of magnitude faster than state-of-the-art modulation spectroscopy setups are demonstrated. The experimental method is based on charge-coupled-device detection, avoiding speed-limiting components, such as polarization modulators with lock-in amplifiers. At the same time, FRS spectra are obtained with a sensitivity of 20 µrad ( 0.001 ° \[0.001{\bm{^\circ }}\] ) over a broad spectral range (525-800 nm), which is on par with state-of-the-art polarization-modulation techniques. The new measurement and analysis technique also automatically cancels unwanted Faraday rotation backgrounds. Using the setup, Faraday rotation spectroscopy of excitons is performed in a hexagonal boron nitride-encapsulated atomically thin semiconductor WS2 under magnetic fields of up to 1.4 T at room temperature and liquid helium temperature. An exciton g-factor of -4.4 ± 0.3 is determined at room temperature, and -4.2 ± 0.2 at liquid helium temperature. In addition, FRS and hysteresis loop measurements are performed on a 20 nm thick film of an amorphous magnetic Tb20 Fe80 alloy.
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Affiliation(s)
- Benjamin Carey
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
- School of Mathematics and Physics, The University of Queensland, Saint Lucia, QLD, 4072, Australia
| | - Nils Kolja Wessling
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
- Institute of Photonics, Department of Physics, University of Strathclyde, Glasgow, G1 1RD, UK
| | - Paul Steeger
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Christoph Klusmann
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Robert Schneider
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Mario Fix
- Institute of Physics, University of Augsburg, 86159, Augsburg, Germany
| | - Robert Schmidt
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Manfred Albrecht
- Institute of Physics, University of Augsburg, 86159, Augsburg, Germany
| | | | - Rudolf Bratschitsch
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Ashish Arora
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
- Department of Physics, Indian Institute of Science Education and Research, Pune, 411008, India
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The polarization and the fundamental sensitivity of 39K ( 133Cs)- 85Rb- 4He hybrid optical pumping spin exchange relaxation free atomic magnetometers. Sci Rep 2017; 7:6776. [PMID: 28755005 PMCID: PMC5533804 DOI: 10.1038/s41598-017-06434-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 06/12/2017] [Indexed: 11/08/2022] Open
Abstract
The hybrid optical pumping spin exchange relaxation free (SERF) atomic magnetometers can realize ultrahigh sensitivity measurement of magnetic field and inertia. We have studied the 85Rb polarization of two types of hybrid optical pumping SERF magnetometers based on 39K-85Rb-4He and 133Cs-85Rb-4He respectively. Then we found that 85Rb polarization varies with the number density of buffer gas 4He and quench gas N2, pumping rate of pump beam and cell temperature respectively, which will provide an experimental guide for the design of the magnetometer. We obtain a general formula on the fundamental sensitivity of the hybrid optical pumping SERF magnetometer due to shot-noise. The formula describes that the fundamental sensitivity of the magnetometer varies with the number density of buffer gas and quench gas, the pumping rate of pump beam, external magnetic field, cell effective radius, measurement volume, cell temperature and measurement time. We obtain a highest fundamental sensitivity of 1.5073 aT/Hz 1/2 (1 aT = 10-18 T) with 39K-85Rb-4He magnetometer between above two types of magnetometers when 85Rb polarization is 0.1116. We estimate the fundamental sensitivity limit of the hybrid optical pumping SERF magnetometer to be superior to 1.8359 × 10-2 aT/Hz 1/2, which is higher than the shot-noise-limited sensitivity of 1 aT/Hz 1/2 of K SERF atomic magnetometer.
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Hu Y, Hu Z, Liu X, Li Y, Zhang J, Yao H, Ding M. Reduction of far off-resonance laser frequency drifts based on the second harmonic of electro-optic modulator detection in the optically pumped magnetometer. APPLIED OPTICS 2017; 56:5927-5932. [PMID: 29047913 DOI: 10.1364/ao.56.005927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 06/26/2017] [Indexed: 06/07/2023]
Abstract
The frequency drifts of the probe laser could be coupled into the calibrated scale factor of the optically pumped magnetometer (OPM) and induce an error of the measurement accuracy. We propose a method to reduce the far off-resonance laser frequency drifts based on the second harmonic of the electro-optic modulator (EOM) detection system in the all-optical K-Rb hybrid pumping magnetometer. Adopting the closed-loop feedback by monitoring the second-harmonic component in real time, the frequency drift of the probe laser has been effectively reduced by about five times to ∼30 MHz/0.5 h at the detuning of 130 GHz and the cell temperature of 443 K. Besides, this technique has been demonstrated to be helpful for reducing the frequency drifts at different detuning points and temperatures. This method is not only suitable for the development of more compact, high-sensitivity OPMs due to the long-term stability improvement with no extra optical path, but also can be applied to other atomic devices and EOM detection systems for reducing the influence of the laser.
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