Browsing by Author "Baydin, Andrey"

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    Engineering chirality at wafer scale with ordered carbon nanotube architectures
    (Springer Nature, 2023) Doumani, Jacques; Lou, Minhan; Dewey, Oliver; Hong, Nina; Fan, Jichao; Baydin, Andrey; Zahn, Keshav; Yomogida, Yohei; Yanagi, Kazuhiro; Pasquali, Matteo; Saito, Riichiro; Kono, Junichiro; Gao, Weilu; Carbon Hub; Smalley-Curl Institute
    Creating artificial matter with controllable chirality in a simple and scalable manner brings new opportunities to diverse areas. Here we show two such methods based on controlled vacuum filtration - twist stacking and mechanical rotation - for fabricating wafer-scale chiral architectures of ordered carbon nanotubes (CNTs) with tunable and large circular dichroism (CD). By controlling the stacking angle and handedness in the twist-stacking approach, we maximize the CD response and achieve a high deep-ultraviolet ellipticity of 40 ± 1 mdeg nm−1. Our theoretical simulations using the transfer matrix method reproduce the experimentally observed CD spectra and further predict that an optimized film of twist-stacked CNTs can exhibit an ellipticity as high as 150 mdeg nm−1, corresponding to a g factor of 0.22. Furthermore, the mechanical rotation method not only accelerates the fabrication of twisted structures but also produces both chiralities simultaneously in a single sample, in a single run, and in a controllable manner. The created wafer-scale objects represent an alternative type of synthetic chiral matter consisting of ordered quantum wires whose macroscopic properties are governed by nanoscopic electronic signatures and can be used to explore chiral phenomena and develop chiral photonic and optoelectronic devices.
  • Thumbnail Image
    Item
    Giant terahertz polarization rotation in ultrathin films of aligned carbon nanotubes
    (Optical Society of America, 2021) Baydin, Andrey; Baydin, Andrey; Komatsu, Natsumi; Tay, Fuyang; Ghosh, Saunab; Makihara, Takuma; Noe, G. Timothy; Kono, Junichiro; Kono, Junichiro; Kono, Junichiro; Kono, Junichiro
    For easy manipulation of polarization states of light for applications in communications, imaging, and information processing, an efficient mechanism is desired for rotating light polarization with a minimum interaction length. Here, we report giant polarization rotations for terahertz (THz) electromagnetic waves in ultrathin (∼45nm), high-density films of aligned carbon nanotubes. We observed polarization rotations of up to ∼20∘ and ∼110∘ for transmitted and reflected THz pulses, respectively. The amount of polarization rotation was a sensitive function of the angle between the incident THz polarization and the nanotube alignment direction, exhibiting a “magic” angle at which the total rotation through transmission and reflection becomes exactly 90°. Our model quantitatively explains these giant rotations as a result of extremely anisotropic optical constants, demonstrating that aligned carbon nanotubes promise ultrathin, broadband, and tunable THz polarization devices.
  • Thumbnail Image
    Item
    Magnetically tuned continuous transition from weak to strong coupling in terahertz magnon polaritons
    (American Physical Society, 2023) Baydin, Andrey; Hayashida, Kenji; Makihara, Takuma; Tay, Fuyang; Ma, Xiaoxuan; Ren, Wei; Ma, Guohong; Noe, G. Timothy; Katayama, Ikufumi; Takeda, Jun; Nojiri, Hiroyuki; Cao, Shixun; Bamba, Motoaki; Kono, Junichiro; Smalley-Curl Institute
    Depending on the relative rates of coupling and dissipation, a light-matter coupled system is either in the weak- or strong-coupling regime. Here, we present a unique system where the coupling rate continuously increases with an externally applied magnetic field while the dissipation rate remains constant, allowing us to monitor a weak-to-strong coupling transition as a function of magnetic field. We observed a Rabi splitting of a terahertz magnon mode in yttrium orthoferrite above a threshold magnetic field of ∼14 T. Based on a microscopic theoretical model, we show that with increasing magnetic field the magnons transition into magnon polaritons through an exceptional point, which will open up new opportunities for in situ control of non-Hermitian systems.
  • Thumbnail Image
    Item
    Observation of colossal terahertz magnetoresistance and magnetocapacitance in a perovskite manganite
    (Optica Publishing Group, 2023) Tay, Fuyang; Chaudhary, Swati; He, Jiaming; Peraca, Nicolas Marquez; Baydin, Andrey; Fiete, Gregory A.; Zhou, Jianshi; Kono, Junichiro; Smalley-Curl Institute
    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 L a 0.875 S r 0.125 M n O 3 at 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.
  • Thumbnail Image
    Item
    Thickness-Dependent Terahertz Permittivity of Epitaxially Grown PbTe Thin Films
    (MDPI, 2023) Kawahala, Nicolas M.; Matos, Daniel A.; Rappl, Paulo H. O.; Abramof, Eduardo; Baydin, Andrey; Kono, Junichiro; Hernandez, Felix G. G.; Smalley-Curl Institute
    The exceptional thermoelectric properties of PbTe are believed to be associated with the incipient ferroelectricity of this material, which is caused by strong electron–phonon coupling that connects phononic and electronic dynamics. Here, we have used terahertz time-domain spectroscopy measurements to generate complex permittivity spectra for a set of epitaxially grown PbTe thin films with thicknesses between 100 nm and 500 nm at temperatures from 10 K to 300 K. Using a Drude–Lorentz model, we retrieved the physical parameters of both the phononic and electronic contributions to the THz permittivity. We observed a strong decrease, or softening, of the transverse optical phonon mode frequency with decreasing temperature, determining a thickness-independent negative ferroelectric-transition critical temperature, while we found a thickness-dependent anharmonic phonon decay lifetime. The electronic contribution to the permittivity was larger in thinner films, and both the carrier density and mobility increased with decreasing temperature in all films. Finally, we detected a thickness-dependent longitudinal optical phonon mode frequency, indicating the presence of plasmon–phonon coupling.
  • Thumbnail Image
    Item
    Time-domain terahertz spectroscopy in high magnetic fields
    (Springer Nature, 2021) Baydin, Andrey; Makihara, Takuma; Peraca, Nicolas Marquez; Kono, Junichiro
    There are a variety of elementary and collective terahertz-frequency excitations in condensed matter whose magnetic field dependence contains significant insight into the states and dynamics of the electrons involved. Often, determining the frequency, temperature, and magnetic field dependence of the optical conductivity tensor, especially in high magnetic fields, can clarify the microscopic physics behind complex many-body behaviors of solids. While there are advanced terahertz spectroscopy techniques as well as high magnetic field generation techniques available, a combination of the two has only been realized relatively recently. Here, we review the current state of terahertz time-domain spectroscopy (THz-TDS) experiments in high magnetic fields. We start with an overview of time-domain terahertz detection schemes with a special focus on how they have been incorporated into optically accessible high-field magnets. Advantages and disadvantages of different types of magnets in performing THz-TDS experiments are also discussed. Finally, we highlight some of the new fascinating physical phenomena that have been revealed by THz-TDS in high magnetic fields.