Nematic Electronic Structure in the “Parent” State of the Iron-Based Superconductor Ca(Fe1–xCox)2As2

Science ◽  
2010 ◽  
Vol 327 (5962) ◽  
pp. 181-184 ◽  
Author(s):  
T.-M. Chuang ◽  
M. P. Allan ◽  
Jinho Lee ◽  
Yang Xie ◽  
Ni Ni ◽  
...  
Keyword(s):  
Electronic Structure ◽  
High Temperature Superconductivity ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Iron Based Superconductors ◽  
Bulk Properties ◽  
Quasiparticle Interference ◽  
Parent State ◽  
Nematic State ◽  
Iron Based

The mechanism of high-temperature superconductivity in the newly discovered iron-based superconductors is unresolved. We use spectroscopic imaging–scanning tunneling microscopy to study the electronic structure of a representative compound CaFe1.94Co0.06As2 in the “parent” state from which this superconductivity emerges. Static, unidirectional electronic nanostructures of dimension eight times the inter–iron-atom distance aFe-Fe and aligned along the crystal a axis are observed. In contrast, the delocalized electronic states detectable by quasiparticle interference imaging are dispersive along the b axis only and are consistent with a nematic α2 band with an apparent band folding having wave vector q≅±22π/8aFe-Fe along the a axis. All these effects rotate through 90 degrees at orthorhombic twin boundaries, indicating that they are bulk properties. As none of these phenomena are expected merely due to crystal symmetry, underdoped ferropnictides may exhibit a more complex electronic nematic state than originally expected.

scholarly journals Two distinct superconducting states controlled by orientations of local wrinkles in LiFeAs

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lu Cao ◽  
Wenyao Liu ◽  
Geng Li ◽  
Guangyang Dai ◽  
Qi Zheng ◽  
...  
Keyword(s):  
Local Strain ◽  
Scanning Tunneling ◽  
Strain Effect ◽  
Type I ◽  
Unconventional Superconductivity ◽  
Type Ii ◽  
Tunneling Microscopy ◽  
Iron Based Superconductors ◽  
Emergent Phenomena ◽  
Iron Based

AbstractFor iron-based superconductors, the phase diagrams under pressure or strain exhibit emergent phenomena between unconventional superconductivity and other electronic orders, varying in different systems. As a stoichiometric superconductor, LiFeAs has no structure phase transitions or entangled electronic states, which manifests an ideal platform to explore the pressure or strain effect on unconventional superconductivity. Here, we observe two types of superconducting states controlled by orientations of local wrinkles on the surface of LiFeAs. Using scanning tunneling microscopy/spectroscopy, we find type-I wrinkles enlarge the superconducting gaps and enhance the transition temperature, whereas type-II wrinkles significantly suppress the superconducting gaps. The vortices on wrinkles show a C2 symmetry, indicating the strain effects on the wrinkles. By statistics, we find that the two types of wrinkles are categorized by their orientations. Our results demonstrate that the local strain effect with different directions can tune the superconducting order parameter of LiFeAs very differently, suggesting that the band shifting induced by directional pressure may play an important role in iron-based superconductivity.

“Wave-Function Imaging” Studies of High-Tc Superconductivity

MRS Bulletin ◽  
2005 ◽  
Vol 30 (6) ◽  
pp. 437-441 ◽  
Author(s):  
James A. Slezak ◽  
Jinho Lee ◽  
J. C. Davis
Keyword(s):  
Electronic Structure ◽  
Momentum Space ◽  
High Temperature Superconductivity ◽  
Inelastic Neutron Scattering ◽  
Real Space ◽  
Inelastic Neutron ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Carrier Doping ◽  
Localized Electrons

AbstractHigh-temperature superconductivity in the cuprates emerges when the localized electrons of a Mott insulator become mobile due to carrier doping. Understanding both the electronic ground state and the excited states of these systems are key challenges in physics today. Angle-resolved photoemission spectroscopy (ARPES) and inelastic neutron-scattering (INS) studies have been remarkably successful in mapping the momentum-space characteristics of the cuprate electronic structure. However, since cuprate superconductivity develops from atomically localized electrons and exhibits nanoscale disorder, a pure momentum-space description is unlikely to be sufficient. Instead, simultaneous information on electronic structure at the nanoscale in real space, and throughout momentum space, is required. Here, we describe a combination of novel spectroscopic imaging scanning tunneling microscopy (SI-STM) techniques that we have developed to achieve these apparently contradictory aims, along with the outcome of a series of SI-STM studies of the electronic structure of Bi2Sr2CaCu2O8+x.

scholarly journals Iron-based high transition temperature superconductors

2014 ◽  
Vol 1 (3) ◽  
pp. 371-395 ◽  
Author(s):  
Xianhui Chen ◽  
Pengcheng Dai ◽  
Donglai Feng ◽  
Tao Xiang ◽  
Fu-Chun Zhang
Keyword(s):  
Transition Temperature ◽  
Point Of View ◽  
Scanning Tunneling ◽  
Electric Transport ◽  
Superconducting Transition ◽  
Tunneling Microscopy ◽  
Iron Based Superconductors ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Iron Based ◽  
Coupling Point

Abstract In a superconductor electrons form pairs and electric transport becomes dissipation-less at low temperatures. Recently discovered iron-based superconductors have the highest superconducting transition temperature next to copper oxides. In this article, we review material aspects and physical properties of iron-based superconductors. We discuss the dependence of transition temperature on the crystal structure, the interplay between antiferromagnetism and superconductivity by examining neutron scattering experiments, and the electronic properties of these compounds obtained by angle-resolved photoemission spectroscopy in link with some results from scanning tunneling microscopy/spectroscopy measurements. Possible microscopic model for this class of compounds is discussed from a strong coupling point of view.

Room temperature observation of the correlation between atomic and electronic structure of graphene on Cu(110)

RSC Advances ◽  
2016 ◽  
Vol 6 (100) ◽  
pp. 98001-98009 ◽  
Author(s):  
Thais Chagas ◽  
Thiago H. R. Cunha ◽  
Matheus J. S. Matos ◽  
Diogo D. dos Reis ◽  
Karolline A. S. Araujo ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Chemical Vapor Deposition ◽  
Scanning Tunneling Microscopy ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Temperature Observation ◽  
Atomic And Electronic Structure

We have used atomically-resolved scanning tunneling microscopy and spectroscopy to study the interplay between the atomic and electronic structure of graphene formed on copper via chemical vapor deposition.

scholarly journals Quasiparticle interference in iron-based superconductors

2010 ◽  
Vol 82 (22) ◽  
Author(s):  
A. Akbari ◽  
J. Knolle ◽  
I. Eremin ◽  
R. Moessner
Keyword(s):  
Iron Based Superconductors ◽  
Quasiparticle Interference ◽  
Iron Based

scholarly journals Nematic state stabilized by off-site Coulomb interaction in iron-based superconductors

2015 ◽  
Vol 92 (8) ◽  
Author(s):  
Xiao-Jun Zheng ◽  
Zhong-Bing Huang ◽  
Da-Yong Liu ◽  
Liang-Jian Zou
Keyword(s):  
Coulomb Interaction ◽  
Iron Based Superconductors ◽  
Nematic State ◽  
Iron Based

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.

Local Electronic Structure in Ordered Aggregates of Carbon Nanotubes: Scanning Tunneling Microscopy/scanning Tunneling Spectroscopy Study

1998 ◽  
Vol 13 (9) ◽  
pp. 2389-2395 ◽  
Author(s):  
D. L. Carroll ◽  
P. M. Ajayan ◽  
S. Curran
Keyword(s):  
Carbon Nanotubes ◽  
Electronic Structure ◽  
Scanning Tunneling Microscopy ◽  
Local Density ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Spatially Resolved ◽  
Local Electronic Structure

The recent application of tunneling probes in electronic structure studies of carbon nanotubes has proven both powerful and challenging. Using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS), local electronic properties in ordered aggregates of carbon nanotubes (multiwalled nanotubes and ropes of single walled nanotubes) have been probed. In this report, we present evidence for interlayer (concentric tube) interactions in multiwalled tubes and tube-tube interactions in singlewalled nanotube ropes. The spatially resolved, local electronic structure, as determined by the local density of electronic states, is shown to clearly reflect tube-tube interactions in both of these aggregate forms.

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