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1. Topological Hall Effect in a Topological Insulator Interfaced with a Magnetic Insulator

   https://doi.org/10.1021/acs.nanolett.0c03195  

   Li, Peng; Ding, Jinjun; Zhang, Steven S.-L.; Kally, James; Pillsbury, Timothy; Heinonen, Olle G.; Rimal, Gaurab; Bi, Chong; DeMann, August; Field, Stuart B.; et al (December 2020, Nano Letters)

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2. Topological insulator laser: Experiments

   https://doi.org/10.1126/science.aar4005  

   Bandres, Miguel A.; Wittek, Steffen; Harari, Gal; Parto, Midya; Ren, Jinhan; Segev, Mordechai; Christodoulides, Demetrios N.; Khajavikhan, Mercedeh (March 2018, Science)
3. Tunable Acoustic Topological Insulator

   Darabi, Amir; Leamy, Michael (June 2019, PHONONICS 2019: 5th International Conference on Phononic Crystals/Metamaterials, Phonon Transport and Topological Phononics)

   Inspired by the quantum spin Hall effect (QSHE), we propose and numerically verify at tuna-ble topological insulator by employing asymmetry and nonlinearity, to exhibit topologically protected edge states (TPES). These properties may open new research directions in realizing the quantized anomalous Hall effects and topological insulators. 

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4. Topological insulator laser: Theory

   https://doi.org/10.1126/science.aar4003  

   Harari, Gal; Bandres, Miguel A.; Lumer, Yaakov; Rechtsman, Mikael C.; Chong, Y. D.; Khajavikhan, Mercedeh; Christodoulides, Demetrios N.; Segev, Mordechai (March 2018, Science)
5. Topological Insulator-Based Electroacoustic Transistors

   https://doi.org/10.1115/DETC2023-116489  

   Kuchibhatla, Sai Aditya; Leamy, Michael J. (August 2023, American Society of Mechanical Engineers)

   We propose an electroacoustic transistor enabled by reconfigurable topological insulators (TIs). The underlying structure of the device is a hexagonal lattice with a unit cell consisting of piezoelectric disks bonded to an aluminum substrate. First, we study the dispersion of flexural waves in the reconfigurable TI to identify Dirac cones in the band structure of a unit cell possessing C6v-symmetry. A topological bandgap can be opened by breaking inversion symmetry in the unit cell. This is achieved by altering the elastic response of one of the affixed piezoelectric disks using a negative impedance shunt circuit. Next, we analyze various topological states formed by interfacing mirror-symmetric unit cells. Sublattices with interface states are then combined to construct a transistor supercell which hosts at least two topologically protected channels for wave propagation. The amplitude of an incoming acoustic signal propagating in one of the topological channels, referred to as the ‘Gate’, is used to switch on or off a second topological channel between a wave source and receiver, mimicking the behavior of a field effect transistor in electronics. We employ finite element analysis to study the harmonic response of the transistor structure demonstrating the OFF and ON states of the device. Further, we present a mock-up of an electrical circuit which enables the switching of the topological channel between a wave source and receiver. The design of the proposed wave-based transistor promises the advantage of topological protection and may find applications in wearable devices, edge computing, and sensing in harsh environments. 

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