scholarly journals Nonlinearity-induced photonic topological insulator

Science ◽  
2020 ◽  
Vol 370 (6517) ◽  
pp. 701-704
Author(s):  
Lukas J. Maczewsky ◽  
Matthias Heinrich ◽  
Mark Kremer ◽  
Sergey K. Ivanov ◽  
Max Ehrhardt ◽  
...  
Keyword(s):  
Lattice Structure ◽  
Optical Power ◽  
Optical Nonlinearity ◽  
Topological Phase ◽  
Transport Channel ◽  
Lattice Disorder ◽  
Topological Features ◽  
Topological System ◽  
Power Threshold ◽  
Hallmark Feature

A hallmark feature of topological insulators is robust edge transport that is impervious to scattering at defects and lattice disorder. We demonstrate a topological system, using a photonic platform, in which the existence of the topological phase is brought about by optical nonlinearity. The lattice structure remains topologically trivial in the linear regime, but as the optical power is increased above a certain power threshold, the system is driven into the topologically nontrivial regime. This transition is marked by the transient emergence of a protected unidirectional transport channel along the edge of the structure. Our work studies topological properties of matter in the nonlinear regime, providing a possible route for the development of compact devices that harness topological features in an on-demand fashion.

scholarly journals Unveiling Signatures of Topological Phases in Open Kitaev Chains and Ladders

Nanomaterials ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 894 ◽  
Author(s):  
Alfonso Maiellaro ◽  
Francesco Romeo ◽  
Carmine Antonio Perroni ◽  
Vittorio Cataudella ◽  
Roberta Citro
Keyword(s):  
Electrical Response ◽  
Differential Conductance ◽  
Model Parameters ◽  
Topological Phases ◽  
Topological Order ◽  
Topological Phase ◽  
Moderate Amount ◽  
Topological System ◽  
Isolated Systems

In this work, the general problem of the characterization of the topological phase of an open quantum system is addressed. In particular, we study the topological properties of Kitaev chains and ladders under the perturbing effect of a current flux injected into the system using an external normal lead and derived from it via a superconducting electrode. After discussing the topological phase diagram of the isolated systems, using a scattering technique within the Bogoliubov–de Gennes formulation, we analyze the differential conductance properties of these topological devices as a function of all relevant model parameters. The relevant problem of implementing local spectroscopic measurements to characterize topological systems is also addressed by studying the system electrical response as a function of the position and the distance of the normal electrode (tip). The results show how the signatures of topological order affect the electrical response of the analyzed systems, a subset of which being robust also against the effects of a moderate amount of disorder. The analysis of the internal modes of the nanodevices demonstrates that topological protection can be lost when quantum states of an initially isolated topological system are hybridized with those of the external reservoirs. The conclusions of this work could be useful in understanding the topological phases of nanowire-based mesoscopic devices.

Third-order optical nonlinearity effect of DNA- and polyvinylpyrrolidone-functionalized carbon nanotubes

2015 ◽  
Vol 24 (01) ◽  
pp. 1550008 ◽  
Author(s):  
Liangmin Zhang ◽  
Benjamin Steckling ◽  
Adrian Lucero ◽  
Andreas Schmitt-Sody ◽  
William White ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Water Solution ◽  
Laser System ◽  
Optical Power ◽  
Optical Nonlinearity ◽  
Optical Absorption Coefficient ◽  
Third Order ◽  
Multiwalled Carbon ◽  
The Third ◽  
Optical Susceptibility

We have used single-stranded DNA (ssDNA) and polyvinylpyrrolidone (PVP) to disperse multiwalled carbon nanotubes (MWNTs) in water solution through sonication and centrifuge procedures. The advantage of these two polymers is that they do not need toxic organic solvents to distribute the carbon nanotubes. The scanning electron microscope (SEM) technique has been used to investigate the interaction between polymer molecules and MWNTs. The images show that MWNTs can be distributed effectively into the two polymer solutions. The third-order optical susceptibility, nonlinear optical absorption coefficient and optical power limiting of these dispersions have been characterized experimentally using a femtosecond laser system with a tunable range of 750–850 nm. The imaginary part of the third-order optical susceptibility has also been computed.

scholarly journals Evidence for dispersing 1D Majorana channels in an iron-based superconductor

Science ◽  
2020 ◽  
Vol 367 (6473) ◽  
pp. 104-108 ◽  
Author(s):  
Zhenyu Wang ◽  
Jorge Olivares Rodriguez ◽  
Lin Jiao ◽  
Sean Howard ◽  
Martin Graham ◽  
...  
Keyword(s):  
Bound States ◽  
Domain Walls ◽  
Lattice Structure ◽  
Condensed Matter ◽  
One Dimension ◽  
Scanning Tunneling ◽  
Majorana Fermions ◽  
Topological Phase ◽  
Linear Dispersion ◽  
Combined Data

The possible realization of Majorana fermions as quasiparticle excitations in condensed-matter physics has created much excitement. Most studies have focused on Majorana bound states; however, propagating Majorana states with linear dispersion have also been predicted. Here, we report scanning tunneling spectroscopic measurements of crystalline domain walls (DWs) in FeSe0.45Te0.55. We located DWs across which the lattice structure shifts by half a unit cell. These DWs have a finite, flat density of states inside the superconducting gap, which is a hallmark of linearly dispersing modes in one dimension. This signature is absent in DWs in the related superconductor, FeSe, which is not in the topological phase. Our combined data are consistent with the observation of dispersing Majorana states at a π-phase shift DW in a proximitized topological material.

scholarly journals Tunneling-induced optical limiting in quantum dot molecules

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Mohadeseh Veisi ◽  
Seyedeh Hamideh Kazemi ◽  
Mohammad Mahmoudi
Keyword(s):  
Quantum Dot ◽  
Optical Power ◽  
Optical Limiting ◽  
Input Voltage ◽  
Optical Nonlinearity ◽  
Saturable Absorption ◽  
Reverse Saturable Absorption ◽  
Absorption Mechanism ◽  
Probe Field ◽  
Limiting Behavior

Abstract We present a convenient way to obtain an optical power limiting behavior in a quantum dot molecule system, induced by an interdot tunneling. Also, the effect of system parameters on the limiting performance is investigated; interestingly, the tunneling rate can affect the limiting performance of the system so that the threshold of the limiting behavior can be a function of the input voltage, allowing the optimization of the limiting action. Furthermore, by investigating the absorption of the probe field, it is demonstrated that the optical limiting is due to a reverse saturable absorption mechanism; indeed, analytical results show that this mechanism is based on a cross-Kerr optical nonlinearity induced by the tunneling. Additionally, the limiting properties of the system are studied by using a Z-scan technique.

Optical Power Limiters for Nanosecond Pulses: Design of New Dendritic Chromophores with Exceptionally Large Two-Photon Cross-Sections

1999 ◽  
Vol 597 ◽  
Author(s):  
E. H. Elandaloussi ◽  
C. Spangler ◽  
M. Casstevens ◽  
D. Kumar ◽  
J. Weibel ◽  
...  
Keyword(s):  
Cross Sections ◽  
Optical Power ◽  
Optical Nonlinearity ◽  
Photon Absorption ◽  
Laser Dyes ◽  
Structure Property ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Structure Property Relationships ◽  
Nanosecond Pulses

AbstractOver the past five years there has been a renaissance in design studies of chromophores with the possibility of enhanced two-photon absorption (TPA). While two-photon absorption has been described for molecules such as laser dyes in solution for a number of years1, it has only been recently that researchers have attempted detailed structure-property relationships to elucidate how new chromophores with greatly enhanced two-photon cross-sections might be designed. Since the intrinsic cross-sections are related to the Im component of the third order optical nonlinearity, it should come as no surprise that much of the previous work in the literature which focused on structure-property relationships for molecules with enhanced NLO response might be applicable to the design of new TPA chromophores. In this presentation we will review our recent studies in this area, and our rationale for the applicability of dendritic strctures based on photonic-active repeat units for enhancment of two-photon absorption, particularly in the area of optical power limiting applications.

scholarly journals Observing multifarious topological phase transitions with real-space indicator

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yong-Heng Lu ◽  
Yao Wang ◽  
Feng Mei ◽  
Yi-Jun Chang ◽  
Hang Zheng ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Three Dimensional ◽  
Real Space ◽  
Second Order ◽  
Topological Phases ◽  
Topological Phase ◽  
Edge States ◽  
Direct Writing ◽  
Topological Features ◽  
Topological Phase Transitions

Abstract First- and second-order topological phases, capable of inherent protection against disorder of materials, have been recently experimentally demonstrated in various artificial materials through observing the topologically protected edge states. Topological phase transition represents a new class of quantum critical phenomena, which is accompanied by the changes related to the bulk topology of energy band structures instead of symmetry. However, it is still a challenge to directly observe the topological phase transitions defined in terms of bulk states. Here, we theoretically and experimentally demonstrate the direct observation of multifarious topological phase transitions with real-space indicator in a single photonic chip, which is formed by integration of 324 × 33 waveguides supporting both first- and second-order topological phases. The trivial-to-first-order, trivial-to-second-order and first-to-second-order topological phase transitions signified by the band gap closure can all be directly detected via photon evolution in the bulk. We further observe the creation and destruction of gapped topological edge states associated with these topological phase transitions. The bulk-state-based route to investigate the high-dimensional and high-order topological features, together with the platform of freely engineering topological materials by three-dimensional laser direct writing in a single photonic chip, opens up a new avenue to explore the mechanisms and applications of artificial devices.

scholarly journals Topological edge and corner states in a two-dimensional photonic Su-Schrieffer-Heeger lattice

Nanophotonics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 3227-3234 ◽  
Author(s):  
Minkyung Kim ◽  
Junsuk Rho
Keyword(s):  
Rotational Symmetry ◽  
Polarization Degree ◽  
Open Boundary ◽  
Topological Phase ◽  
Two Dimensional ◽  
Topological Properties ◽  
Open Boundary Condition ◽  
Metallic Nanoparticle ◽  
Topological Features ◽  
Longitudinal Edge

AbstractImplementation of topology on photonics has opened new functionalities of photonic systems such as topologically protected boundary modes. We theoretically present polarization-dependent topological properties in a 2D Su-Schrieffer-Heeger lattice by using a metallic nanoparticle array and considering the polarization degree of freedom. We demonstrate that when eigenmodes are polarized parallel to the plane of the 2D lattice, it supports longitudinal edge modes that are isolated from the bulk states and transverse edge modes that are overlapped with the bulk states. Also, the in-plane polarized modes support a second-order topological phase under an open boundary condition by breaking the four-fold rotational symmetry. This work will offer polarization-based multifunctionality in compact photonic systems that have topological features.

scholarly journals Topological Phase Transition in a One-Dimensional Elastic String System

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 313 ◽  
Author(s):  
Ya-Wen Tsai ◽  
Yao-Ting Wang ◽  
Pi-Gang Luan ◽  
Ta-Jen Yen
Keyword(s):  
Phase Transition ◽  
Domain Wall ◽  
Transmittance Spectrum ◽  
Topological Phase ◽  
One Dimensional ◽  
Topological Features ◽  
Topological Phase Transition ◽  
Elastic String ◽  
Interface Mode

We show that topological interface mode can emerge in a one-dimensional elastic string system which consists of two periodic strings with different band topologies. To verify their topological features, Zak-phase of each band is calculated and reveals the condition of topological phase transition accordingly. Apart from that, the transmittance spectrum illustrates that topological interface mode arises when two topologically distinct structures are connected. The vibration profile further exhibits the non-trivial interface mode in the domain wall between two periodic string composites.

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