More Like this

1. Observation of colossal terahertz magnetoresistance and magnetocapacitance in a perovskite manganite

   https://doi.org/10.1364/OPTICA.491626  

   Tay, Fuyang; Chaudhary, Swati; He, Jiaming; Marquez_Peraca, Nicolas; Baydin, Andrey; Fiete, Gregory_A; Zhou, Jianshi; Kono, Junichiro (July 2023, Optica)

   Terahertz (THz) magnetoresistance effects have been extensively investigated and have shown promising results for applications in magnetic modulations of the amplitude of THz waves. However, THz magnetocapacitance in dielectric systems, which is essential for phase modulations of THz radiation, remains largely unexplored. Here, we study the THz response of a bulk single crystal of La_0.875Sr_0.125MnO₃at around its Curie temperature, observing significant magnetic-field-induced changes in the THz resistance and capacitance extracted from the optical conductivity. We discuss possible mechanisms for the observed coexistence of colossal THz magnetoresistance and magnetocapacitance in a perovskite manganite that is not multiferroic. This work enhances our understanding of colossal magnetoresistance in a complex system with THz spectroscopy and demonstrates potential use of perovskite manganites in THz technology. 

   more » « less
2. Nonlinear photocarrier dynamics in multilayer W S e ₂ induced by intense terahertz pulses

   https://doi.org/10.1364/JOSAB.504204  

   Guay, Viela; Johnson, Nathan; Zhang, Yue; van_der_Zande, Arend_M; Thorp, Spencer_G; Graham, Matthew; Lee, Yun-Shik (November 2023, Journal of the Optical Society of America B)

   Non-equilibrium photocarriers in multilayer WSe₂injected by femtosecond laser pulses exhibit extraordinary nonlinear dynamics in the presence of intense THz fields. The THz absorption in optically excited WSe₂rises rapidly in the low THz field regime and gradually ramps up at high intensities. The strong THz pulses drive the photocarriers into sidebands of higher mobility and release trapped charge carriers, which consequently enhance the transient conductivity of WSe₂. The spectrally analyzed conductivity reveals distinctive features, indicating that the photocarriers undergo resonant interactions such as carrier-photon scattering. 

   more » « less
3. Excitation and detection of coherent sub-terahertz magnons in ferromagnetic and antiferromagnetic heterostructures

   https://doi.org/10.1038/s41524-022-00851-2  

   Zhuang, Shihao; Hu, Jia-Mian (August 2022, npj Computational Materials)

   Abstract Excitation of coherent high-frequency magnons (quanta of spin waves) is critical to the development of high-speed magnonic devices. Here we computationally demonstrate the excitation of coherent sub-terahertz (THz) magnons in ferromagnetic (FM) and antiferromagnetic (AFM) thin films by a photoinduced picosecond acoustic pulse. Analytical calculations are also performed to reveal the magnon excitation mechanism. Through spin pumping and spin-charge conversion, these magnons can inject sub-THz charge current into an adjacent heavy-metal film which in turn emits electromagnetic (EM) waves. Using a dynamical phase-field model that considers the coupled dynamics of acoustic waves, spin waves, and EM waves, we show that the emitted EM wave retains the spectral information of all the sub-THz magnon modes and has a sufficiently large amplitude for near-field detection. These predictions indicate that the excitation and detection of sub-THz magnons can be realized in rationally designed FM or AFM thin-film heterostructures via ultrafast optical-pump THz-emission-probe spectroscopy. 

   more » « less
4. Colossal Terahertz Emission with Ultrafast Tunability Based on Van der Waals Ferroelectric NbOI ₂

   https://doi.org/10.1002/adom.202403471  

   Subedi, Sujan; Liu, Wenhao; Fang, Wuzhang; Fox, Carter; Zhai, Zixin; Fei, Fan; Ping, Yuan; Lv, Bing; Xiao, Jun (February 2025, Advanced Optical Materials)

   Abstract Terahertz (THz) technology is critical for quantum material physics, biomedical imaging, ultrafast electronics, and next‐generation wireless communications. However, standing in the way of widespread applications is the scarcity of efficient ultrafast THz sources with on‐demand fast modulation and easy on‐chip integration capability. Here the discovery of colossal THz emission is reported from a van der Waals (vdW) ferroelectric semiconductor NbOI₂. Using THz emission spectroscopy, a THz generation efficiency an order of magnitude higher than that of ZnTe, a standard nonlinear crystal for ultrafast THz generation is observed. The underlying generation mechanisms associated are further uncovered with its large ferroelectric polarization by studying the THz emission dependence on excitation wavelength, incident polarization, and fluence. Moreover, the ultrafast coherent amplification and annihilation of the THz emission and associated coherent phonon oscillations by employing a double‐pump scheme are demonstrated. These findings combined with first‐principles calculations, inform a new understanding of the THz light–matter interaction in emergent vdW ferroelectrics and pave the way to develop high‐performance THz devices on them for quantum materials sensing and ultrafast electronics. 

   more » « less
5. In-plane hyperbolic polariton tuners in terahertz and long-wave infrared regimes

   https://doi.org/10.1038/s41467-023-38214-0  

   Huang, Wuchao; Folland, Thomas G.; Sun, Fengsheng; Zheng, Zebo; Xu, Ningsheng; Xing, Qiaoxia; Jiang, Jingyao; Chen, Huanjun; Caldwell, Joshua D.; Yan, Hugen; et al (May 2023, Nature Communications)

   Abstract One of the main bottlenecks in the development of terahertz (THz) and long-wave infrared (LWIR) technologies is the limited intrinsic response of traditional materials. Hyperbolic phonon polaritons (HPhPs) of van der Waals semiconductors couple strongly with THz and LWIR radiation. However, the mismatch of photon − polariton momentum makes far-field excitation of HPhPs challenging. Here, we propose an In-Plane Hyperbolic Polariton Tuner that is based on patterning van der Waals semiconductors, here α-MoO₃, into ribbon arrays. We demonstrate that such tuners respond directly to far-field excitation and give rise to LWIR and THz resonances with high quality factors up to 300, which are strongly dependent on in-plane hyperbolic polariton of the patterned α-MoO₃. We further show that with this tuner, intensity regulation of reflected and transmitted electromagnetic waves, as well as their wavelength and polarization selection can be achieved. Our results can help the development of THz and LWIR miniaturized devices. 

   more » « less