scholarly journals Large spatial extension of the zero-energy Yu–Shiba–Rusinov state in a magnetic field

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Zoltán Scherübl ◽  
Gergő Fülöp ◽  
Cătălin Paşcu Moca ◽  
Jörg Gramich ◽  
Andreas Baumgartner ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Bound States ◽  
Scanning Tunneling ◽  
Zero Energy ◽  
Tunneling Microscopy ◽  
Numerical Renormalization Group ◽  
Andreev Bound States ◽  
Semiconductor Quantum Dot ◽  
Spatial Extension ◽  
The One

AbstractVarious promising qubit concepts have been put forward recently based on engineered superconductor subgap states like Andreev bound states, Majorana zero modes or the Yu-Shiba-Rusinov (Shiba) states. The coupling of these subgap states via a superconductor strongly depends on their spatial extension and is an essential next step for future quantum technologies. Here we investigate the spatial extension of a Shiba state in a semiconductor quantum dot coupled to a superconductor. With detailed transport measurements and numerical renormalization group calculations we find a remarkable more than 50 nm extension of the zero energy Shiba state, much larger than the one observed in very recent scanning tunneling microscopy measurements. Moreover, we demonstrate that its spatial extension increases substantially in a magnetic field.

scholarly journals Evolution of quasi-bound states in the circular n–p junction of bilayer graphene under magnetic field

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Haijiao Ji ◽  
Yueting Pan ◽  
Haiwen Liu
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Bound States ◽  
Local Density ◽  
Energy Levels ◽  
Bilayer Graphene ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Weak Magnetic Fields ◽  
The Magnetic Field

Abstract Electron in gapless bilayer graphene can form quasi-bound states when a circular symmetric potential is created in bilayer graphene. These quasi-bound states can be adjusted by tuning the radius and strength of the potential barrier. We investigate the evolution of quasi-bound states spectra in the circular n–p junction of bilayer graphene under the magnetic field numerically. The energy levels of opposite angular momentum split and the splitting increases with the magnetic field. Moreover, weak magnetic fields can slightly shift the energy levels of quasi-bound states. While strong magnetic fields induce additional resonances in the local density states, which originates from Landau levels. We demonstrate that these numerical results are consistent with the semiclassical analysis based on Wentzel–Kramers–Brillouin approximation. Our results can be verified experimentally via scanning tunneling microscopy measurements.

STM studies of crystal growth

1991 ◽  
Vol 49 ◽  
pp. 374-375
Author(s):  
M. G. Lagally
Keyword(s):  
Crystal Growth ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Sputter Deposition ◽  
Field Of View ◽  
Scanning Tunneling ◽  
Wide Field ◽  
Tunneling Microscopy ◽  
Wide Field Of View ◽  
The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

scholarly journals MAGNETIC FIELD TUNING OF CHARGE AND SPIN ORDER IN THE CUPRATE SUPERCONDUCTORS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3156-3163 ◽  
Author(s):  
A. POLKOVNIKOV ◽  
S. SACHDEV ◽  
M. VOJTA ◽  
E. DEMLER
Keyword(s):  
Magnetic Field ◽  
Ground State ◽  
Charge Density Wave ◽  
Cuprate Superconductors ◽  
Density Wave ◽  
Spin Density Wave ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Spin Order ◽  
New Information

Recent neutron scattering, nuclear magnetic resonance, and scanning tunneling microscopy experiments have yielded valuable new information on the interplay between charge and spin density wave order and superconductivity in the cuprate superconductors, by using a perpendicular magnetic field to tune the ground state properties. We compare the results of these experiments with the predictions of a theory which assumed that the ordinary superconductor was proximate to a quantum transition to a superconductor with co-existing spin/charge density wave order.

Mapping of local electronic properties in nanostructured CMR thin films by Scanning Tunneling Microscopy (STM) and Local Conductance Map (LCMAP)

2004 ◽  
Vol 838 ◽  
Author(s):  
Sohini Kar ◽  
Barnali Ghosh ◽  
L. K. Brar ◽  
M A. Paranjape ◽  
A. K. Raychaudhuri
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Grain Boundaries ◽  
Electronic Properties ◽  
Variable Temperature ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Colossal Magnetoresistive ◽  
Spatially Resolved ◽  
Temperature Scanning

ABSTRACTWe have investigated the local electronic properties and the spatially resolved magnetoresistance of a nanostructured film of a colossal magnetoresistive (CMR) material by local conductance mapping (LCMAP) using a variable temperature Scanning Tunneling Microscope (STM) operating in a magnetic field. The nanostructured thin films (thickness ≈500nm) of the CMR material La0.67Sr0.33MnO3(LSMO) on quartz substrates were prepared using chemical solution deposition (CSD) process. The CSD grown films were imaged by both STM and atomic force microscopy (AFM). Due to the presence of a large number of grain boundaries (GB's), these films show low field magnetoresistance (LFMR) which increases at lower temperatures.The measurement of spatially resolved electronic properties reveal the extent of variation of the density of states (DOS) at and close to the Fermi level (EF) across the grain boundaries and its role in the electrical resistance of the GB. Measurement of the local conductance maps (LCMAP) as a function of magnetic field as well as temperature reveals that the LFMR occurs at the GB. While it was known that LFMR in CMR films originates from the GB, this is the first investigation that maps the local electronic properties at a GB in a magnetic field and traces the origin of LFMR at the GB.

STM STUDIES OF ELECTRONIC ORDER IN THE UNDERDOPED SURFACE OF YBa2Cu3Oy

2007 ◽  
Vol 21 (18n19) ◽  
pp. 3199-3201
Author(s):  
TERUKAZU NISHIZAKI ◽  
NORIO KOBAYASHI ◽  
MAKOTO MAKI
Keyword(s):  
Low Temperature ◽  
Scanning Tunneling ◽  
Long Range Order ◽  
Tunneling Microscopy ◽  
One Dimensional ◽  
Stm Image ◽  
Temperature Scanning ◽  
The One ◽  
Carrier Doping ◽  
Electronic Order

To study the nanoscale electronic order in high-T c superconductors, we have performed low-temperature scanning tunneling microscopy (STM) experiments on YBa 2 Cu 3 O y, single crystals. The electronic state of the underdoped CuO 2 plane is studied through the BaO surface taking advantage of the cleaved surface, which has an insufficient carrier doping into the topmost CuO 2 plane because of the incomplete carrier reservoir. The STM image measured at low bias-voltage below 20 mV shows the one-dimensional (1D) electronic modulation along the Cu - O bonds. The 1D modulation do not have long-range order and the periodicity varies within the range ~ 2a - 4a depending on the position on the surface. These results indicate that electronic order in underdoped YBa 2 Cu 3 O y, differs from the 4a×4a checkerboard structure observed in Bi 2 Sr 2 CaCu 2 O y and Ca 2-x Na x CuO 2 Cl 2.

scholarly journals Recent progresses of quantum confinement in graphene quantum dots

2021 ◽  
Vol 17 (3) ◽  
Author(s):  
Si-Yu Li ◽  
Lin He
Keyword(s):  
Quantum Dots ◽  
Quantum Confinement ◽  
Bound States ◽  
Berry Phase ◽  
Graphene Quantum Dots ◽  
Bound State ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Dirac Fermions ◽  
Tunneling Microscopy

AbstractGraphene quantum dots (GQDs) not only have potential applications on spin qubit, but also serve as essential platforms to study the fundamental properties of Dirac fermions, such as Klein tunneling and Berry phase. By now, the study of quantum confinement in GQDs still attract much attention in condensed matter physics. In this article, we review the experimental progresses on quantum confinement in GQDs mainly by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Here, the GQDs are divided into Klein GQDs, bound-state GQDs and edge-terminated GQDs according to their different confinement strength. Based on the realization of quasi-bound states in Klein GQDs, external perpendicular magnetic field is utilized as a manipulation approach to trigger and control the novel properties by tuning Berry phase and electron-electron (e-e) interaction. The tip-induced edge-free GQDs can serve as an intuitive mean to explore the broken symmetry states at nanoscale and single-electron accuracy, which are expected to be used in studying physical properties of different two-dimensional materials. Moreover, high-spin magnetic ground states are successfully introduced in edge-terminated GQDs by designing and synthesizing triangulene zigzag nanographenes.

scholarly journals Zero-energy bound states in the high-temperature superconductors at the two-dimensional limit

2020 ◽  
Vol 6 (13) ◽  
pp. eaax7547 ◽  
Author(s):  
Chaofei Liu ◽  
Cheng Chen ◽  
Xiaoqiang Liu ◽  
Ziqiao Wang ◽  
Yi Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Bound States ◽  
High Temperature Superconductors ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Two Dimensional ◽  
Zero Energy ◽  
Topological Superconductors ◽  
Topological Quantum ◽  
Energy Bound

Majorana zero modes (MZMs) that obey the non-Abelian statistics have been intensively investigated for potential applications in topological quantum computing. The prevailing signals in tunneling experiments “fingerprinting” the existence of MZMs are the zero-energy bound states (ZEBSs). However, nearly all of the previously reported ZEBSs showing signatures of the MZMs are observed in difficult-to-fabricate heterostructures at very low temperatures and additionally require applied magnetic field. Here, by using in situ scanning tunneling spectroscopy, we detect the ZEBSs upon the interstitial Fe adatoms deposited on two different high-temperature superconducting one-unit-cell iron chalcogenides on SrTiO3(001). The spectroscopic results resemble the phenomenological characteristics of the MZMs inside the vortex cores of topological superconductors. Our experimental findings may extend the MZM explorations in connate topological superconductors toward an applicable temperature regime and down to the two-dimensional (2D) limit.

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.

Scanning Tunneling Microscopy and Spectroscopy of (LaSe)1.14(NbSe2) at Very Low Temperatures and in Magnetic Field

2004 ◽  
Vol 54 (S4) ◽  
pp. 489-492 ◽  
Author(s):  
J. Kačmarčík ◽  
P. Szabó ◽  
P. Samuely ◽  
J.G. Rodrigo ◽  
H. Suderow ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Scanning Tunneling Microscopy ◽  
Low Temperatures ◽  
Scanning Tunneling ◽  
Tunneling Microscopy
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