scholarly journals Observation of a Majorana zero mode in a topologically protected edge channel

Science ◽  
2019 ◽  
Vol 364 (6447) ◽  
pp. 1255-1259 ◽  
Author(s):  
Berthold Jäck ◽  
Yonglong Xie ◽  
Jian Li ◽  
Sangjun Jeon ◽  
B. Andrei Bernevig ◽  
...  
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Zero Mode ◽  
Scanning Tunneling ◽  
Zero Energy ◽  
Tunneling Microscopy ◽  
Model Calculations ◽  
Iron Clusters ◽  
Edge Channel ◽  
Zero Modes ◽  
Gap States

Superconducting proximity pairing in helical edge modes, such as those of topological insulators, is predicted to provide a unique platform for realizing Majorana zero modes (MZMs). We used scanning tunneling microscopy measurements to probe the influence of proximity-induced superconductivity and magnetism on the helical hinge states of bismuth(111) films grown on a superconducting niobium substrate and decorated with magnetic iron clusters. Consistent with model calculations, our measurements revealed the emergence of a localized MZM at the interface between the superconducting helical edge channel and the iron clusters, with a strong magnetization component along the edge. Our experiments also resolve the MZM’s spin signature, which distinguishes it from trivial in-gap states that may accidentally occur at zero energy in a superconductor.

scholarly journals Distinguishing a Majorana zero mode using spin-resolved measurements

Science ◽  
2017 ◽  
Vol 358 (6364) ◽  
pp. 772-776 ◽  
Author(s):  
Sangjun Jeon ◽  
Yonglong Xie ◽  
Jian Li ◽  
Zhijun Wang ◽  
B. Andrei Bernevig ◽  
...  
Keyword(s):  
Spin Polarization ◽  
Zero Mode ◽  
Direct Consequence ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Model Calculations ◽  
One Dimensional ◽  
Topological Superconductors ◽  
Spin Polarized ◽  
Gap States

One-dimensional topological superconductors host Majorana zero modes (MZMs), the nonlocal property of which could be exploited for quantum computing applications. We use spin-polarized scanning tunneling microscopy to show that MZMs realized in self-assembled Fe chains on the surface of Pb have a spin polarization that exceeds that stemming from the magnetism of these chains. This feature, captured by our model calculations, is a direct consequence of the nonlocality of the Hilbert space of MZMs emerging from a topological band structure. Our study establishes spin-polarization measurements as a diagnostic tool to distinguish topological MZMs from trivial in-gap states of a superconductor.

scholarly journals Majorana zero modes in impurity-assisted vortex of LiFeAs superconductor

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lingyuan Kong ◽  
Lu Cao ◽  
Shiyu Zhu ◽  
Michał Papaj ◽  
Guangyang Dai ◽  
...  
Keyword(s):  
Quantum Computation ◽  
Zero Mode ◽  
Scanning Tunneling ◽  
Homogeneous Material ◽  
Dirac Fermions ◽  
Tunneling Microscopy ◽  
Zero Modes ◽  
Topological Quantum ◽  
One Step ◽  
Topological Quantum Computation

AbstractThe iron-based superconductor is emerging as a promising platform for Majorana zero mode, which can be used to implement topological quantum computation. One of the most significant advances of this platform is the appearance of large vortex level spacing that strongly protects Majorana zero mode from other low-lying quasiparticles. Despite the advantages in the context of physics research, the inhomogeneity of various aspects hampers the practical construction of topological qubits in the compounds studied so far. Here we show that the stoichiometric superconductor LiFeAs is a good candidate to overcome this obstacle. By using scanning tunneling microscopy, we discover that the Majorana zero modes, which are absent on the natural clean surface, can appear in vortices influenced by native impurities. Our detailed analysis reveals a new mechanism for the emergence of those Majorana zero modes, i.e. native tuning of bulk Dirac fermions. The discovery of Majorana zero modes in this homogeneous material, with a promise of tunability, offers an ideal material platform for manipulating and braiding Majorana zero modes, pushing one step forward towards topological quantum computation.

scholarly journals A new Majorana platform in an Fe-As bilayer superconductor

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Wenyao Liu ◽  
Lu Cao ◽  
Shiyu Zhu ◽  
Lingyuan Kong ◽  
Guangwei Wang ◽  
...  
Keyword(s):  
Bound States ◽  
Zero Mode ◽  
Surface States ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Iron Pnictide ◽  
Iron Chalcogenide ◽  
Zero Modes ◽  
Topological Quantum ◽  
Iron Chalcogenide Superconductors

Abstract Iron-chalcogenide superconductors have emerged as a promising Majorana platform for topological quantum computation. By combining topological band and superconductivity in a single material, they provide significant advantage to realize isolated Majorana zero modes. However, iron-chalcogenide superconductors, especially Fe(Te,Se), suffer from strong inhomogeneity which may hamper their practical application. In addition, some iron-pnictide superconductors have been demonstrated to have topological surface states, yet no Majorana zero mode has been observed inside their vortices, raising a question of universality about this new Majorana platform. In this work, through angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy measurement, we identify Dirac surface states and Majorana zero modes, respectively, for the first time in an iron-pnictide superconductor, CaKFe4As4. More strikingly, the multiple vortex bound states with integer-quantization sequences can be accurately reproduced by our model calculation, firmly establishing Majorana nature of the zero mode.

Modified gap states in Fe/MgO/SrTiO3 interfaces studied with scanning tunneling microscopy

2014 ◽  
Vol 14 (12) ◽  
pp. 1692-1695 ◽  
Author(s):  
Hyung-Joon Shin ◽  
Seong Heon Kim ◽  
Heejun Yang ◽  
Young Kuk
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Gap States

Photon Scanning Tunneling Microscopy of Optical Wavegnide Structures

1994 ◽  
Vol 332 ◽  
Author(s):  
Ahn Goo Choo ◽  
Mona H. Chudgar ◽  
Howard E Jackson ◽  
Gregory N. De Brabander ◽  
Mukesh Kumar ◽  
...  
Keyword(s):  
Refractive Index ◽  
Scanning Tunneling Microscopy ◽  
Scanning Tunneling ◽  
Optical Channel ◽  
Refractive Indices ◽  
Tunneling Microscopy ◽  
Model Calculations ◽  
Semiconductor Heterostructure ◽  
Channel Waveguides ◽  
Tapered Optical Fiber

ABSTRACTPhoton scanning tunneling microscopy (PSTM) has been used to obtain effective refractive indices of optical channel waveguide structures. The local evanescent field intensity associated with the propagation modes of optical channel waveguides are measured at two different wavelengths. Both a tapered optical fiber tip and a semiconductor heterostructure tip are employed for detection. Local values of effective refractive index are measured for both TE and TM polarizations and compared to model calculations.

A study on α-RuCl3 crystal structure by scanning tunneling microscopy

1989 ◽  
Vol 47 ◽  
pp. 30-31
Author(s):  
H.-J. Cantow ◽  
H. Hillebrecht ◽  
S. Magonov ◽  
H. W. Rotter ◽  
G. Thiele
Keyword(s):  
Crystal Structure ◽  
Density Distribution ◽  
Scanning Tunneling Microscopy ◽  
Electron Density ◽  
Structure Determination ◽  
Electron Density Distribution ◽  
Scanning Tunneling ◽  
Monoclinic Space Group ◽  
Tunneling Microscopy ◽  
X Ray

From X-ray analysis, the conclusions are drawn from averaged molecular informations. Thus, limitations are caused when analyzing systems whose symmetry is reduced due to interatomic interactions. In contrast, scanning tunneling microscopy (STM) directly images atomic scale surface electron density distribution, with a resolution up to fractions of Angstrom units. The crucial point is the correlation between the electron density distribution and the localization of individual atoms, which is reasonable in many cases. Thus, the use of STM images for crystal structure determination may be permitted. We tried to apply RuCl3 - a layered material with semiconductive properties - for such STM studies. From the X-ray analysis it has been assumed that α-form of this compound crystallizes in the monoclinic space group C2/m (AICI3 type). The chlorine atoms form an almost undistorted cubic closed package while Ru occupies 2/3 of the octahedral holes in every second layer building up a plane hexagon net (graphite net). Idealizing the arrangement of the chlorines a hexagonal symmetry would be expected. X-ray structure determination of isotypic compounds e.g. IrBr3 leads only to averaged positions of the metal atoms as there exist extended stacking faults of the metal layers.

Roughness measurements of nonlinear optical polymer films by scanning tunneling microscopy

1989 ◽  
Vol 47 ◽  
pp. 22-23
Author(s):  
I. H. Musselman ◽  
R.-T. Chen ◽  
P. E. Russell
Keyword(s):  
Surface Roughness ◽  
Scanning Tunneling Microscopy ◽  
Nonlinear Optical ◽  
Polymer Surface ◽  
Light Extinction ◽  
Scanning Tunneling ◽  
Silicon Substrates ◽  
Tunneling Microscopy ◽  
Optical Polymer ◽  
Total Light

Scanning tunneling microscopy (STM) has been used to characterize the surface roughness of nonlinear optical (NLO) polymers. A review of STM of polymer surfaces is included in this volume. The NLO polymers are instrumental in the development of electrooptical waveguide devices, the most fundamental of which is the modulator. The most common modulator design is the Mach Zehnder interferometer, in which the input light is split into two legs and then recombined into a common output within the two dimensional waveguide. A π phase retardation, resulting in total light extinction at the output of the interferometer, can be achieved by changing the refractive index of one leg with respect to the other using the electrooptic effect. For best device performance, it is essential that the NLO polymer exhibit minimal surface roughness in order to reduce light scattering. Scanning tunneling microscopy, with its high lateral and vertical resolution, is capable of quantifying the NLO polymer surface roughness induced by processing. Results are presented below in which STM was used to measure the surface roughness of films produced by spin-coating NLO-active polymers onto silicon substrates.

Practical applications of scanning tunneling microscopy

1989 ◽  
Vol 47 ◽  
pp. 18-19
Author(s):  
D. R. Denley
Keyword(s):  
High Resolution ◽  
Scanning Tunneling Microscopy ◽  
Quantitative Information ◽  
Digital Data ◽  
Scanning Tunneling ◽  
Ambient Atmosphere ◽  
Tunneling Microscopy ◽  
Clear Trend ◽  
Practical Applications ◽  
Promising Tool

Scanning tunneling microscopy (STM) has recently been introduced as a promising tool for analyzing surface atomic structure. We have used STM for its extremely high resolution (especially the direction normal to surfaces) and its ability for imaging in ambient atmosphere. We have examined surfaces of metals, semiconductors, and molecules deposited on these materials to achieve atomic resolution in favorable cases.When the high resolution capability is coupled with digital data acquisition, it is simple to get quantitative information on surface texture. This is illustrated for the measurement of surface roughness of evaporated gold films as a function of deposition temperature and annealing time in Figure 1. These results show a clear trend for which the roughness, as well as the experimental deviance of the roughness is found to be minimal for evaporation at 300°C. It is also possible to contrast different measures of roughness.

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