scholarly journals Point-contact Andreev reflection spectroscopy on Bi2Se3 single crystals

2016 ◽  
Vol 30 (13) ◽  
pp. 1642002 ◽  
Author(s):  
C. R. Granstrom ◽  
I. Fridman ◽  
H.-C. Lei ◽  
C. Petrovic ◽  
J. Y. T. Wei
Keyword(s):  
Single Crystals ◽  
Andreev Reflection ◽  
Surface Condition ◽  
Three Dimensional ◽  
Point Contact ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Zero Bias ◽  
Zero Bias Conductance

To study how Andreev reflection (AR) occurs between a superconductor and a three-dimensional topological insulator (TI), we use superconducting Nb tips to perform point-contact AR spectroscopy at 4.2 K on as-grown single crystals of Bi2Se3. Scanning tunneling spectroscopy and scanning tunneling microscopy are also used to characterize the superconducting tip and both the doping level and surface condition of the TI sample. The point-contact measurements show clear spectral signatures of AR, as well as a depression of zero-bias conductance with decreasing junction impedance. The latter observation can be attributed to interfacial Rashba spin-orbit coupling, and the presence of bulk bands at the Fermi level in our samples suggests that bulk states of Bi2Se3 are involved in the observed AR.

scholarly journals Scalable Majorana vortex modes in iron-based superconductors

2020 ◽  
Vol 6 (9) ◽  
pp. eaay0443 ◽  
Author(s):  
Ching-Kai Chiu ◽  
T. Machida ◽  
Yingyi Huang ◽  
T. Hanaguri ◽  
Fu-Chun Zhang
Keyword(s):  
Tight Binding ◽  
Three Dimensional ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Zero Energy ◽  
Binding Model ◽  
Zero Bias ◽  
Iron Based Superconductors ◽  
Iron Based ◽  
Important Indication

The iron-based superconductor FeTexSe1−x is one of the material candidates hosting Majorana vortex modes residing in the vortex cores. It has been observed by recent scanning tunneling spectroscopy measurement that the fraction of vortex cores having zero-bias peaks decreases with increasing magnetic field on the surface of FeTexSe1−x. The hybridization of two Majorana vortex modes cannot simply explain this phenomenon. We construct a three-dimensional tight-binding model simulating the physics of over a hundred Majorana vortex modes in FeTexSe1−x. Our simulation shows that the Majorana hybridization and disordered vortex distribution can explain the decreasing fraction of the zero-bias peaks observed in the experiment; the statistics of the energy peaks off zero energy in our Majorana simulation are in agreement with the experiment. These agreements lead to an important indication of scalable Majorana vortex modes in FeTexSe1−x. Thus, FeTexSe1−x can be one promising platform having scalable Majorana qubits for quantum computing.

Scanning Tunneling Spectroscopy in Anisotropic s-Wave Superconductors

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3300-3303 ◽  
Author(s):  
H. Suderow ◽  
J. G. Rodrigo ◽  
P. Martinez-Samper ◽  
S. Vieira ◽  
J. P. Brison ◽  
...  
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Single Crystals ◽  
Low Temperatures ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Superconducting Gap ◽  
S Wave ◽  
Tunneling Microscopy

We discuss Scanning Tunneling Microscopy and Spectroscopy (STM/S) measurements at very low temperatures in single crystals of the non magnetic borocarbide superconductors RNi 2 B 2 C ( R = Y , Lu , T c=15.5 and 16.5 K) and in MgB 2. The tunneling spectra in some regions of the surface show a clear reduction of the anisotropy of the superconducting gap.

scholarly journals Zero-bias conductance peak in detached flakes of superconducting 2H-TaS2probed by scanning tunneling spectroscopy

2014 ◽  
Vol 89 (22) ◽  
Author(s):  
J. A. Galvis ◽  
L. Chirolli ◽  
I. Guillamón ◽  
S. Vieira ◽  
E. Navarro-Moratalla ◽  
...  
Keyword(s):  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Zero Bias ◽  
Conductance Peak ◽  
Zero Bias Conductance

scholarly journals Two-dimensional polyaniline (C3N) from carbonized organic single crystals in solid state

2016 ◽  
Vol 113 (27) ◽  
pp. 7414-7419 ◽  
Author(s):  
Javeed Mahmood ◽  
Eun Kwang Lee ◽  
Minbok Jung ◽  
Dongbin Shin ◽  
Hyun-Jung Choi ◽  
...  
Keyword(s):  
Solid State ◽  
Single Crystals ◽  
Density Functional ◽  
Density Functional Theory Calculation ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Phenyl Rings ◽  
Device Applications ◽  
Principle Density Functional Theory

The formation of 2D polyaniline (PANI) has attracted considerable interest due to its expected electronic and optoelectronic properties. Although PANI was discovered over 150 y ago, obtaining an atomically well-defined 2D PANI framework has been a longstanding challenge. Here, we describe the synthesis of 2D PANI via the direct pyrolysis of hexaaminobenzene trihydrochloride single crystals in solid state. The 2D PANI consists of three phenyl rings sharing six nitrogen atoms, and its structural unit has the empirical formula of C3N. The topological and electronic structures of the 2D PANI were revealed by scanning tunneling microscopy and scanning tunneling spectroscopy combined with a first-principle density functional theory calculation. The electronic properties of pristine 2D PANI films (undoped) showed ambipolar behaviors with a Dirac point of –37 V and an average conductivity of 0.72 S/cm. After doping with hydrochloric acid, the conductivity jumped to 1.41 × 103 S/cm, which is the highest value for doped PANI reported to date. Although the structure of 2D PANI is analogous to graphene, it contains uniformly distributed nitrogen atoms for multifunctionality; hence, we anticipate that 2D PANI has strong potential, from wet chemistry to device applications, beyond linear PANI and other 2D materials.

Scanning-tunneling spectroscopy on conjugated polymer films

2003 ◽  
Vol 771 ◽  
Author(s):  
M. Kemerink ◽  
S.F. Alvarado ◽  
P.M. Koenraad ◽  
R.A.J. Janssen ◽  
H.W.M. Salemink ◽  
...  
Keyword(s):  
Polymer Films ◽  
Conjugated Polymer ◽  
Three Dimensional ◽  
Field Enhancement ◽  
Direct Consequence ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Band Alignment ◽  
Scanning Tunneling ◽  
Order Of Magnitude

AbstractScanning-tunneling spectroscopy experiments have been performed on conjugated polymer films and have been compared to a three-dimensional numerical model for charge injection and transport. It is found that field enhancement near the tip apex leads to significant changes in the injected current, which can amount to more than an order of magnitude, and can even change the polarity of the dominant charge carrier. As a direct consequence, the single-particle band gap and band alignment of the organic material can be directly obtained from tip height-voltage (z-V) curves, provided that the tip has a sufficiently sharp apex.

scholarly journals Imaging and identification of point defects in PtTe2

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Kuanysh Zhussupbekov ◽  
Lida Ansari ◽  
John B. McManus ◽  
Ainur Zhussupbekova ◽  
Igor V. Shvets ◽  
...  
Keyword(s):  
Point Defects ◽  
Density Functional ◽  
Transition Metal Dichalcogenides ◽  
Density Functional Theory Calculations ◽  
Charge Carrier Mobility ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Recombination Rates ◽  
And Performance

AbstractThe properties and performance of two-dimensional (2D) materials can be greatly affected by point defects. PtTe2, a 2D material that belongs to the group 10 transition metal dichalcogenides, is a type-II Dirac semimetal, which has gained a lot of attention recently due to its potential for applications in catalysis, photonics, and spintronics. Here, we provide an experimental and theoretical investigation of point defects on and near the surface of PtTe2. Using scanning tunneling microscopy and scanning tunneling spectroscopy (STS) measurements, in combination with first-principle calculations, we identify and characterize five common surface and subsurface point defects. The influence of these defects on the electronic structure of PtTe2 is explored in detail through grid STS measurements and complementary density functional theory calculations. We believe these findings will be of significance to future efforts to engineer point defects in PtTe2, which is an interesting and enticing approach to tune the charge-carrier mobility and electron–hole recombination rates, as well as the site reactivity for catalysis.

Stm Studies at Electrochemically Controlled Interfaces

1994 ◽  
Vol 332 ◽  
Author(s):  
S.M. Lindsay ◽  
J. Pan ◽  
T.W. Jing
Keyword(s):  
Electron Tunneling ◽  
Point Contact ◽  
Localized States ◽  
Scanning Tunneling ◽  
Zero Field ◽  
Tunneling Microscopy ◽  
Dna Oligomers ◽  
Synthetic Dna ◽  
Quantum Point

ABSTRACTWe use electrochemical methods to control the adsorption of molecules onto an electrode for imaging in-situ by scanning tunneling microscopy. Measurements of the barrier for electron tunneling show that the mechanism of electron transfer differs from vacuum tunneling. Barriers depend upon the direction of electron tunneling, indicating the presence of permanently aligned dipoles in the tunnel gap. We attribute a sharp dip in the barrier near zero field to induced polarization. We propose a ‘tunneling’ process consisting of two parts: One is delocalization of quantum-coherent states in parts of the molecular adlayer that hybridize strongly (interaction ≥ kT) with Bloch states in the metal. This gives rise to a quantum-point-contact conductance, Gc ≤ 2e2/h at a height zo. The other part comes from the exponential decay of the tails of localized states, G = Gc exp{−2K(z − z0)}. Because measured decay lengths, (2K‘)−1, are small (≈ 1 Å), STM contrast is dominated by the contour along which G[z0 (x,y)] = Gc. Measured changes in z0 are used to calculate images which are in reasonable agreement with observations. We illustrate this with images of synthetic DNA oligomers.

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