Bulletin of the American Physical Society
Mid-Atlantic Section Fall Meeting 2020
Volume 65, Number 20
Friday–Sunday, December 4–6, 2020; Virtual
Session B05: Topological Materials I |
Hide Abstracts |
Chair: Seongshik Oh, Rutgers University |
Friday, December 4, 2020 2:00PM - 2:36PM |
B05.00001: Spin-charge Interconversion in Topological Quantum Materials Invited Speaker: Nitin Samarth The study of spin-to-charge interconversion in topological quantum materials is of fundamental interest because of the fascinating interplay between spin-orbit coupling, spin texture, and underlying symmetries. The observation of high efficiency spin-to-charge interconversion in topological insulators at room temperature has in particular motivated the recent emergence of ``topological spintronics" as a basis for non-volatile memory and energy efficient spin-based logic. We first provide an overview of this field and then discuss recent measurements of spin-to-charge interconversion in the archetypal Dirac semimetal $\mathrm{Cd_3As_2}$, detected by both spin torque ferromagnetic resonance and spin pumping. We observe behavior consistent with previously reported spin-to-charge interconversion mechanisms in heavy metals, topological insulators, and Weyl semimetals. We also find that the efficiency of these phenomena is comparable to that due to the spin Hall effect in heavy metals. Finally, we compare our results with first principles calculations and discuss the origins of the observed effects. Work carried out with Wilson Yanez, Yongxi Ou, Run Xiao, Jacob Held, Jahyun Koo, Timothy Pillsbury, Anthony Richardella, Andre Mkhoyan, and Binghai Yan. [Preview Abstract] |
Friday, December 4, 2020 2:36PM - 2:48PM |
B05.00002: Bardeen-Cooper-Schrieffer pairing of composite fermions Anirban Sharma, Songyang Pu, Jainendra Jain The pairing of composite fermions is thought to lead to remarkable physics, such as the topological superconductivity and non-Abelian Majorana modes [1,2]. We investigate the problem by constructing a p-wave paired BCS wave function of composite fermions [3] on torus geometry and minimizing the energy as a function of the gap parameter. Our results show clear evidence of pairing at $\nu=5/2$, but no evidence of pairing at $\nu=1/2$. We find that the lowest energy BCS function has the highest overlap with the Pfaffian wavefunction. We search for but do not find the spin-singlet pairing of composite fermions at $\nu=1/2$. We also consider other pairing symmetries and investigate the Hall viscosity for the BCS wavefunction in different phases. \\ $\left[1\right]$ G. Moore and N. Read, Nucl. Phys. B 360, 362 (1991) \\ $\left[2\right]$ N. Read and D. Green, Phys. Rev. B 61, 10267 (2000) \\ $\left[3\right]$ G. M\”{o}ller and S. H. Simon, Phys. Rev. B 77,075319 (2008) [Preview Abstract] |
Friday, December 4, 2020 2:48PM - 3:00PM |
B05.00003: Observation of Flat Frequency Bands at Open Edges and Antiphase Boundary Seams in Topological Mechanical Metamaterials Kai Qian, Linghua Zhu, Keun Hyuk Ahn, Camelia Prodan In this talk, we report the observation of the flat frequency bands of the topological origin at open edges and antiphase boundary seams in mechanical metamaterials [1], as predicted by the recent theoretical studies on a two-dimensional chiral Hamiltonian [2]. It is experimentally and computationally demonstrated that topological flat bands can occur at open edges of planar systems and antiphase boundary seams of ring or tubular systems. We also show that the flatness of the edge bands and the size of the localized states can be controlled by the distance between open edges, and compare with the theory. This study suggests that similar flat bands could occur in other metamaterials, such as photonic crystals and electronic metamaterials. Reference: [1] K. Qian, L. Zhu, K. H. Ahn, and C. Prodan, Phys. Rev. Lett. (accepted). [2] L. Zhu, E. Prodan, and K. H. Ahn, Phys. Rev. B 99, 041117(R) (2019). [Preview Abstract] |
Friday, December 4, 2020 3:00PM - 3:12PM |
B05.00004: Experimental Demonstration of Dynamic Topological Pumping Across Incommensurate Bilayered Acoustic Metamaterials Wenting Cheng, Emil Prodan, Camelia Prodan In this talk, we reported the first un-assisted dynamic energy transfer across a metamaterial, via pumping of such topological edge modes. The system is a topological aperiodic acoustic crystal, with a phason that can be fast and periodically driven in adiabatic cycles. The system is characterized experimentally by standard acoustic measurements, and via a finite element approach utilizing COMSOL Multiphysics. When one edge of the metamaterial is excited in a topological forbidden range of frequencies, a microphone placed at the other edge starts to pick up a signal as soon as the pumping process is set in motion. In contrast, the microphone picks no signal when the forbidden range of frequencies is non-topological. This study suggests possible applications of electron pumping in conventional insulators. [Preview Abstract] |
Friday, December 4, 2020 3:12PM - 3:24PM |
B05.00005: Nonlocal Kinetic Energy Functional Enables Reliable Large-scale Electronic Structure Simulations Wenhui Mi, Michele Pavanello Orbital-Free DFT (OF-DFT) and subsystem DFT (sDFT) are two promising approaches for large-scale electronic structure simulations, owing to their computational cost is linear scaling with system size. The common central ingredient of these two approaches is the kinetic energy functional (KEDF) which determines the accuracy of the performance. Unfortunately, with the available KEDFs, systems having highly inhomogeneous electron densities still fall outside OF-DFT's range of applicability. In sDFT, Currently employed KEDFs are at most semi-local, and simulations only included systems composed of weakly interacting subsystems. Recently, we made considerable progress in addressing this problem by proposing a new generation of nonlocal KEDFs that features correct asymptotic and ability to handle highly inhomogeneous electron densities. With these KEDFs, OF-DFT achieves close to chemical accuracy for the electronic energy for quantum dots and metal clusters. Benchmarks for the various bonded systems show that the new nonlocal sDFT considerably improves the computed interaction energies and electron densities compared to commonly employed (semi) local sDFT. Our work shows that the new generation of nonlocal KEDF enables both OF-DFT and sDFT for reliable large-scale simulations. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700