Mesoscale And Nanoscale Physics
Large Anomalous Hall Effect in Topological Insulators with Proximitized Ferromagnetic Insulators (1906.02159v1)
Masataka Mogi, Taro Nakajima, Victor Ukleev, Atsushi Tsukazaki, Ryutaro Yoshimi, Minoru Kawamura, Kei S Takahashi, Takayasu Hanashima, Kazuhisa Kakurai, Taka-hisa Arima, Masashi Kawasaki, Yoshinori Tokura
We report a proximity-driven large anomalous Hall effect in all-telluride heterostructures consisting of ferromagnetic insulator Cr2Ge2Te6 and topological insulator (Bi,Sb)2Te3. Despite small magnetization in the (Bi,Sb)2Te3 layer, the anomalous Hall conductivity reaches a large value of 0.2e2/h in accord with a ferromagnetic response of the Cr2Ge2Te6. The results show that the exchange coupling between the surface state of the topological insulator and the proximitized Cr2Ge2Te6 layer is effective and strong enough to open the sizable exchange gap in the surface state.
Low-loss Broadband Dirac Plasmons in Borophene (1803.01604v2)
Chao Lian, Shi-Qi Hu, Jin Zhang, Cai Cheng, Zhe Yuan, Shiwu Gao, Sheng Meng
The past decade has witnessed numerous discoveries of two-dimensional (2D) semimetals and insulators, whereas 2D metals are rarely identified. Borophene, a monolayer boron sheet, has recently emerged as a perfect 2D metal with unique structure and electronic properties. Here we study collective excitations in borophene, which exhibit two major plasmon modes with low damping rates extending from infrared to ultraviolet regime. The anisotropic 1D plasmon originates from electronic excitations of tilted Dirac cones in borophene, analogous to that in heavily doped Dirac semimetals. These features make borophene promising to realize directional polariton transportation and broadband optical communications for next-generation optoelectronic devices.
Superconductivity in twisted Graphene heterostructures (1903.00475v2)
Yohanes S. Gani, Hadar Steinberg, Enrico Rossi
We study the low-energy electronic structure of heterostructures formed by one sheet of graphene placed on a monolayer of . We build a continuous low-energy effective model that takes into account the presence of a twist angle between graphene and , and of spin-orbit coupling and superconducting pairing in . We obtain the parameters entering the continuous model via ab-initio calculations. We show that despite the large mismatch between the graphene's and 's lattice constants, due to the large size of the 's Fermi pockets, there is a large range of values of twist angles for which a superconducting pairing can be induced into the graphene layer. In addition, we show that the superconducting gap induced into the graphene is extremely robust to an external in-plane magnetic field. Our results show that the size of the induced superconducting gap, and its robustness against in-plane magnetic fields, can be significantly tuned by varying the twist angle.
John J. L. Morton, Patrice Bertet
Quantum information, encoded within the states of quantum systems, represents a novel and rich form of information which has inspired new types of computers and communications systems. Many diverse electron spin systems have been studied with a view to storing quantum information, including molecular radicals, point defects and impurities in inorganic systems, and quantum dots in semiconductor devices. In these systems, spin coherence times can exceed seconds, single spins can be addressed through electrical and optical methods, and new spin systems with advantageous properties continue to be identified. Spin ensembles strongly coupled to microwave resonators can, in principle, be used to store the coherent states of single microwave photons, enabling so-called microwave quantum memories. We discuss key requirements in realising such memories, including considerations for superconducting resonators whose frequency can be tuned onto resonance with the spins. Finally, progress towards microwave quantum memories and other developments in the field of superconducting quantum devices are being used to push the limits of sensitivity of inductively-detected electron spin resonance. The state-of-the-art currently stands at around 65 spins per root-Hz, with prospects to scale down to even fewer spins.
Raul Perea-Causin, Samuel Brem, Roberto Rosati, Roland Jago, Marvin Kulig, Jonas D. Ziegler, Jonas Zipfel, Alexey Chernikov, Ermin Malic
The interplay of optics, dynamics and transport is crucial for the design of novel optoelectronic devices, such as photodetectors and solar cells. In this context, transition metal dichalcogenides (TMDs) have received much attention. Here, strongly bound excitons dominate optical excitation, carrier dynamics and diffusion processes. While the first two have been intensively studied, there is a lack of fundamental understanding of non-equilibrium phenomena associated with exciton transport that is of central importance e.g. for high efficiency light harvesting. In this work, we provide microscopic insights into the interplay of exciton propagation and many-particle interactions in TMDs. Based on a fully quantum mechanical approach and in excellent agreement with photoluminescence measurements, we show that Auger recombination and emission of hot phonons act as a heating mechanism giving rise to strong spatial gradients in excitonic temperature. The resulting thermal drift leads to an unconventional exciton diffusion characterized by spatial exciton halos.
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