S. Belling, Y. C. Li, A. Davoody, A. Gabourie, I. Knezevic
{"title":"DECaNT: Simulation tool for diffusion of excitons in carbon nanotube films","authors":"S. Belling, Y. C. Li, A. Davoody, A. Gabourie, I. Knezevic","doi":"10.1063/5.0034600","DOIUrl":"https://doi.org/10.1063/5.0034600","url":null,"abstract":"We present the numerical tool DECaNT (Diffusion of Excitons in Carbon NanoTubes) that simulates exciton transport in thin films of carbon nanotubes. Through a mesh of nanotubes generated using the Bullet Physics C++ library, excitons move according to an ensemble Monte Carlo algorithm, with the scattering rates that account for tube chirality, orientation, and distance. We calculate the diffusion tensor from the position--position correlation functions and analyze its anisotropy and dependence on the film composition, morphology, and defect density.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"6 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87314039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Pezo, B. Focassio, G. R. Schleder, M. Costa, C. Lewenkopf, A. Fazzio
{"title":"Disorder effects of vacancies on the electronic transport properties of realistic topological insulator nanoribbons: The case of bismuthene","authors":"A. Pezo, B. Focassio, G. R. Schleder, M. Costa, C. Lewenkopf, A. Fazzio","doi":"10.1103/PHYSREVMATERIALS.5.014204","DOIUrl":"https://doi.org/10.1103/PHYSREVMATERIALS.5.014204","url":null,"abstract":"The robustness of topological materials against disorder and defects is presumed but has not been demonstrated explicitly in realistic systems. In this work, we use state-of-the-art density functional theory and recursive nonequilibrium Green's functions methods to study the effect of disorder in the electronic transport of long nanoribbons, up to 157 nm, as a function of vacancy concentration. In narrow nanoribbons, even for small vacancy concentrations, defect-like localized states give rise to hybridization between the edge states erasing topological protection and enabling backscattering events. We show that the topological protection is more robust for wide nanoribbons, but surprisingly it breaks down at moderate structural disorder. Our study helps to establish some bounds on defective bismuthene nanoribbons as promising candidates for spintronic applications.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85575531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Topological correspondence between magnetic space group representations and subdimensions","authors":"Adrien Bouhon, Gunnar F. Lange, Robert-Jan Slager","doi":"10.1103/PhysRevB.103.245127","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.245127","url":null,"abstract":"The past years have seen rapid progress in the classification of topological band structures using symmetry eigenvalue indicated methods. Given their importance in condensed matter systems, these ideas are increasingly getting explored in the pertinent context of magnetic structures. We here adopt this viewpoint to address the physical implications of extending space groups to magnetic variants. In particular, we introduce a simple model as a generic example of magnetic fragile topology. Most interestingly, we find that this antiferromagnetic-compatible model can be tuned via Zeeman terms to a ferro/ferrimagnetic (FM) counterpart in the same space-group family. This correspondence manifests itself by ensuring that the fragile topology produces bands of finite Chern number in the FM phase. In addition, we discuss how the system can be tuned into a stable topological semimetallic phase, characterized by a simple expression for the $mathbf{Z}_2$ symmetry indicator that results from the combination of $C_4$ symmetry and $C_2T$-protected Euler class topology. This scenario features a similar correspondence that can even relate to higher Chern numbers. Pointing out the generality of such relations for a variety of space group families, we believe our results pave the way for new pursuits in magnetic topologies.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80316232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Chaudhuri, M. Salehi, S. Dasgupta, Mintu Mondal, J. Moon, D. Jain, Seongshik Oh, N. P. Armitage
{"title":"Ambipolar magneto-optical response of ultralow carrier density topological insulators","authors":"D. Chaudhuri, M. Salehi, S. Dasgupta, Mintu Mondal, J. Moon, D. Jain, Seongshik Oh, N. P. Armitage","doi":"10.1103/PHYSREVB.103.L081110","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.L081110","url":null,"abstract":"We have investigated the THz range magneto-optical response of ultralow carrier density films of Sb$_2$Te$_3$ using time-domain THz polarimetry. Undoped Sb$_2$Te$_3$ has a chemical potential that lies inside the bulk valence band. Thus its topological response is masked by bulk carriers. However, with appropriate buffer layer engineering and chemical doping, Sb$_2$Te$_3$ thin films can be grown with extremely low electron or hole densities. The ultralow carrier density samples show unusual optical properties and quantized response in the presence of magnetic fields. Consistent with the expectations for Dirac fermions, a quantized Hall response is seen even in samples where the zero field conductivity falls below detectable levels. The discontinuity in the Faraday angle with small changes in the filling fraction across zero is manifestation of the parity anomaly in 2D Dirac systems with broken time reversal symmetry.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78481890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Theory of the low-temperature longitudinal spin Seebeck effect","authors":"R. Schmidt, P. Brouwer","doi":"10.1103/PHYSREVB.103.014412","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.014412","url":null,"abstract":"Using a simplified microscopic model of coupled spin and lattice excitations in a ferromagnetic insulator we evaluate the magnetic-field dependence of the spin Seebeck effect at low temperatures. The model includes Heisenberg exchange coupling, a harmonic lattice potential, and a pseudo-dipolar exchange interaction. Our approach goes beyond previous work [Phys. Rev. B 98, 134421 (2018)] in that it does not rely on the a priori assumption of a fast equilibration of the magnon and phonon distributions. Our theory shows that singular features in the magnetic-field dependence of the spin Seebeck effect at low temperatures observed by Kikkawa et al. [Phys. Rev. Lett. 117, 207203 (2016)] are independent of the relative strength of magnon-impurity and phonon-impurity scattering.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"67 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75912780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Abrantes, G. Bastos, D. Szilard, C. Farina, F. Rosa
{"title":"Tuning resonance energy transfer with magneto-optical properties of graphene","authors":"P. Abrantes, G. Bastos, D. Szilard, C. Farina, F. Rosa","doi":"10.1103/PhysRevB.103.174421","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.174421","url":null,"abstract":"We investigate the resonance energy transfer (RET) rate between two quantum emitters near a suspended graphene sheet in vacuum under the influence of an external magnetic field. We perform the analysis for low and room temperatures and show that, due to the extraordinary magneto-optical response of graphene, it allows for an active control and tunability of the RET even in the case of room temperature. We also demonstrate that the RET rate is extremely sensitive to small variations of the applied magnetic field, and can be tuned up to a striking six orders of magnitude for quite realistic values of magnetic field. Moreover, we evidence the fundamental role played by the magnetoplasmon polaritons supported by the graphene monolayer as the dominant channel for the RET within a certain distance range. Our results suggest that magneto-optical media may take the manipulation of energy transfer between quantum emitters to a whole new level, and broaden even more its great spectrum of applications.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88935362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Theory of the Strain Engineering of Graphene Nanoconstrictions","authors":"M. Hayashi, H. Yoshioka, H. Tomori, A. Kanda","doi":"10.7566/JPSJ.90.023701","DOIUrl":"https://doi.org/10.7566/JPSJ.90.023701","url":null,"abstract":"Strain engineering is one of the key technologies for using graphene as an electronic device: the strain-induced pseudo-gauge field reflects Dirac electrons, thus opening the so-called conduction gap. Since strain accumulates in constrictions, graphene nanoconstrictions can be a good platform for this technology. On the other hand, in the graphene nanoconstrictions, Fabry-Perot type quantum interference dominates the electrical conduction at low bias voltages. We argue that these two effects have different strain dependence; the pseudo-gauge field contribution is symmetric with respect to positive (tensile) and negative (compressive) strain, whereas the quantum interference is antisymmetric. As a result, a peculiar strain dependence of the conductance appears even at room temperatures.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90964050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. P. Maciel, A. L. Ara'ujo, C. Lewenkopf, G. J. Ferreira
{"title":"Fabry-Pérot resonant vortices and magnetoconductance in topological insulator constrictions with magnetic barriers","authors":"R. P. Maciel, A. L. Ara'ujo, C. Lewenkopf, G. J. Ferreira","doi":"10.1103/PhysRevB.103.205124","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.205124","url":null,"abstract":"The edge states of two-dimensional time-reversal topological insulators (TIs) support a perfect helical conductance on wide ribbons due to the absence of backscattering. Here, we study the changes in the transport properties of TI nanoribbons by introducing a constriction along the ribbon. This set up allows the edge states to hybridize, leading to reflections at the ends of the constriction. We find that the electronic states running along one edge can be reflected back along the opposite edge multiple times, giving rise to Fabry-Perot resonant vortexes within the constriction with well defined conductance peaks. We show that magnetic barriers allow one to manipulate these peaks and obtain significant changes in the system spin-resolved magnetoconductance.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84586457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Hijano, T. L. van den Berg, D. Frustaglia, D. Bercioux
{"title":"Quantum network approach to spin interferometry driven by Abelian and non-Abelian fields","authors":"A. Hijano, T. L. van den Berg, D. Frustaglia, D. Bercioux","doi":"10.1103/PHYSREVB.103.155419","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.155419","url":null,"abstract":"We present a theory of conducting quantum networks that accounts for Abelian and non-Abelian fields acting on spin carriers. We apply this approach to model the conductance of mesoscopic spin interferometers of different geometry (such as squares and rings), reproducing recent experimental findings in pattered InAsGa quantum wells subject to Rashba spin-orbit and Zeeman fields. Moreover, by introducing some additional field-texture engineering, we manage to single out a previously unnoticed spin-phase suppression mechanisms. We observe that our approach also applies to the study of complex networks and the spectral properties of closed systems.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88625127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. A. Solovev, I. I. Yanibekov, Y. Efimov, S. A. Eliseev, V. A. Lovcjus, I. Yugova, S. Poltavtsev, Y. Kapitonov
{"title":"Long-lived dark coherence brought to light by magnetic-field controlled photon echo","authors":"I. A. Solovev, I. I. Yanibekov, Y. Efimov, S. A. Eliseev, V. A. Lovcjus, I. Yugova, S. Poltavtsev, Y. Kapitonov","doi":"10.1103/PhysRevB.103.235312","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.235312","url":null,"abstract":"Larmor precession of the quasiparticle spin about a transverse magnetic field leads to the oscillations in the spontaneous photon echo signal due to the shuffling of the optical coherence between optically accessible (bright) and inaccessible (dark) states. Here we report on a new non-oscillating photon echo regime observed in the presence of non-equal dephasing rates of bright and dark states. This regime enables the observation of the long-living dark optical coherence. As a simple mechanical analogy, we suggest a charged particle moving in the magnetic field through the medium with anisotropic viscous friction. We demonstrate the dark coherence retrieval in the spontaneous photon echo from excitons in the InGaAs/GaAs quantum well.","PeriodicalId":8465,"journal":{"name":"arXiv: Mesoscale and Nanoscale Physics","volume":"96 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78557004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}