scholarly journals Nanoscale strain engineering of giant pseudo-magnetic fields, valley polarization, and topological channels in graphene

2020 ◽  
Vol 6 (19) ◽  
pp. eaat9488 ◽  
Author(s):  
C.-C. Hsu ◽  
M. L. Teague ◽  
J.-Q. Wang ◽  
N.-C. Yeh
Keyword(s):  
Magnetic Fields ◽  
Domain Walls ◽  
Quantum Hall ◽  
Strain Engineering ◽  
Scanning Tunneling ◽  
Monolayer Graphene ◽  
Tunneling Microscopy ◽  
One Dimensional ◽  
Valley Polarization ◽  
Topological States

The existence of nontrivial Berry phases associated with two inequivalent valleys in graphene provides interesting opportunities for investigating the valley-projected topological states. Examples of such studies include observation of anomalous quantum Hall effect in monolayer graphene, demonstration of topological zero modes in “molecular graphene” assembled by scanning tunneling microscopy, and detection of topological valley transport either in graphene superlattices or at bilayer graphene domain walls. However, all aforementioned experiments involved nonscalable approaches of either mechanically exfoliated flakes or atom-by-atom constructions. Here, we report an approach to manipulating the topological states in monolayer graphene via nanoscale strain engineering at room temperature. By placing strain-free monolayer graphene on architected nanostructures to induce global inversion symmetry breaking, we demonstrate the development of giant pseudo-magnetic fields (up to ~800 T), valley polarization, and periodic one-dimensional topological channels for protected propagation of chiral modes in strained graphene, thus paving a pathway toward scalable graphene-based valleytronics.

HIDDEN ORDER AND PSEUDOGAP OF Pb-SUBSTITUTED Bi2201 STUDIED BY SCANNING TUNNELING MICROSCOPY AND OUT-OF-PLANE RESISTIVITY IN MAGNETIC FIELDS

2007 ◽  
Vol 21 (18n19) ◽  
pp. 3208-3210 ◽  
Author(s):  
KAZUTAKA KUDO ◽  
TERUKAZU NISHIZAKI ◽  
NAOYUKI OKUMURA ◽  
TAKAHIKO SASAKI ◽  
NORIO KOBAYASHI ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Magnetic Fields ◽  
Scanning Tunneling Microscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
One Dimensional ◽  
Hidden Order ◽  
Out Of Plane ◽  
The One ◽  
Stm Images

We have performed measurements of the out-of-plane resistivity ρ c in magnetic fields up to 40 T and the scanning tunneling microscopy (STM) in the Pb -Substituted Bi 2201. Two kinds of pseudogaps PG1 and PG2 are found at T*1 and T*2 below which the nonmetallic ρ c starts to develop and to be suppressed in magnetic fields with decreasing temperature, respectively. The obtained phase diagram indicates that the pseudogap related to the superconductivity is not PG1 but PG2. STM images of the Bi(Pb) - O plane in the optimally doped sample show bright atom-strings at V ≤ 10 mV . The observed structure may indicate the one-dimensional correlation which is different from the 4a × 4a structure reported in other systems.

scholarly journals Describing chain-like assembly of ethoxygroup-functionalized organic molecules on Au(111) using high-throughput simulations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Lokamani ◽  
Jeffrey Kelling ◽  
Robin Ohmann ◽  
Jörg Meyer ◽  
Tim Kühne ◽  
...  
Keyword(s):  
High Throughput ◽  
Energy Function ◽  
Organic Molecules ◽  
Molecular Wires ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Intermolecular Interaction Energy ◽  
One Dimensional ◽  
Coverage Density ◽  
Clustering Approach

AbstractDue to the low corrugation of the Au(111) surface, 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene (PEEB) molecules can form quasi interlocked lateral patterns, which are observed in scanning tunneling microscopy experiments at low temperatures. We demonstrate a multi-dimensional clustering approach to quantify the anisotropic pair-wise interaction of molecules and explain these patterns. We perform high-throughput calculations to evaluate an energy function, which incorporates the adsorption energy of single PEEB molecules on the metal surface and the intermolecular interaction energy of a pair of PEEB molecules. The analysis of the energy function reveals, that, depending on coverage density, specific types of pattern are preferred which can potentially be exploited to form one-dimensional molecular wires on Au(111).

scholarly journals The effect of moiré superstructures on topological edge states in twisted bismuthene homojunctions

2020 ◽  
Vol 6 (23) ◽  
pp. eaba2773 ◽  
Author(s):  
Jian Gou ◽  
Longjuan Kong ◽  
Xiaoyue He ◽  
Yu Li Huang ◽  
Jiatao Sun ◽  
...  
Keyword(s):  
Single Layer ◽  
Scanning Tunneling ◽  
Edge States ◽  
First Principles Calculations ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Spatially Distributed ◽  
Topological States ◽  
Device Applications

Creating and controlling the topological properties of two-dimensional topological insulators is essential for spintronic device applications. Here, we report the successful growth of bismuth homostructure consisting of monolayer bismuthene and single-layer black phosphorus–like Bi (BP-Bi) on the HOPG surface. Combining scanning tunneling microscopy/spectroscopy with noncontact atomic force microscopy, moiré superstructures with twist angles in the bismuth homostructure and the modulation of topological edge states of bismuthene were observed and studied. First-principles calculations reproduced the moiré superlattice and indicated that the structure fluctuation is ascribed to the stacking modes between bismuthene and BP-Bi, which induce spatially distributed interface interactions in the bismuth homostructure. The modulation of topological edge states is directly related to the variation of interlayer interactions. Our results suggest a promising pathway to tailor the topological states through interfacial interactions.

Atomic Structure of the Domain Walls of the Discommensurate Phases in Ge(111)/Ga

1998 ◽  
Vol 05 (01) ◽  
pp. 175-179 ◽  
Author(s):  
Zheng Gai ◽  
Bo Gao ◽  
Hang Ji ◽  
R. G. Zhao ◽  
W. S. Yang
Keyword(s):  
Domain Wall ◽  
Scanning Tunneling Microscopy ◽  
Atomic Structure ◽  
Domain Walls ◽  
Scanning Tunneling ◽  
Wall Structure ◽  
Tunneling Microscopy ◽  
Domain Wall Structure ◽  
Stm Images

We have studied the γ and β discommensurate phases of the Ge(111)/Ga system with scanning tunneling microscopy (STM). On the basis of the features of these phases known from our STM images as well as from previous papers, models of domain-wall structure of both phases have been proposed for further investigations.

Island decay on the anisotropic Ag(110) surface

2000 ◽  
Vol 648 ◽  
Author(s):  
Karina Morgenstern ◽  
Erik Lægsgaard ◽  
Flemming Besenbacher
Keyword(s):  
Decay Mode ◽  
Ostwald Ripening ◽  
Variable Temperature ◽  
Scanning Tunneling ◽  
Two Dimensional ◽  
Tunneling Microscopy ◽  
Sharp Transition ◽  
One Dimensional ◽  
Temperature Scanning ◽  
Rate Limiting

AbstractWe have investigated the decay of two-dimensional islands on the anisotropic Ag(110) surface using variable-temperature scanning tunneling microscopy. Contrary to predictions from traditional Ostwald ripening theory, a quasi-one-dimensional decay mode is observed at low temperatures (175-220 K). A surprisingly sharp transition to the quasi-two-dimensional decay mode is observed around 220 K. This transition is accompanied by a fast equilibration of the island shape. These findings have tentatively been rationalized within a simple model to identify the underlying rate limiting atomistic processes.

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.

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