Search results for "Weak localization"
showing 6 items of 6 documents
Quantum localization and bound state formation in Bose-Einstein condensates
2010
We discuss the possibility of exponential quantum localization in systems of ultracold bosonic atoms with repulsive interactions in open optical lattices without disorder. We show that exponential localization occurs in the maximally excited state of the lowest energy band. We establish the conditions under which the presence of the upper energy bands can be neglected, determine the successive stages and the quantum phase boundaries at which localization occurs, and discuss schemes to detect it experimentally by visibility measurements. The discussed mechanism is a particular type of quantum localization that is intuitively understood in terms of the interplay between nonlinearity and a bou…
Impact of nitrogen doping on the band structure and the charge carrier scattering in monolayer graphene
2021
The addition of nitrogen as a dopant in monolayer graphene is a flexible approach to tune the electronic properties of graphene as required for applications. Here, we investigate the impact of the doping process that adds N dopants and defects on the key electronic properties, such as the mobility, the effective mass, the Berry phase, and the scattering times of the charge carriers. Measurements at low temperatures and magnetic fields up to 9 T show a decrease of the mobility with increasing defect density due to elastic, short-range scattering. At low magnetic fields weak localization indicates an inelastic contribution depending on both defects and dopants. Analysis of the effective mass …
Silicon quantum point contact with aluminum gate
2000
Fabrication and electrical properties of silicon quantum point contacts are reported. The devices are fabricated on bonded silicon on insulator (SOI) wafers by combining CMOS process steps and e-beam lithography. Mobility of 9000 cm2 Vs−1 is measured for a 60 nm-thick SOI film at 10 K. Weak localization data is used to estimate the phase coherence length at 4.2 K The point contacts show step like behaviour in linear response conductance at 1.5 K. At 200 mK universal conductance fluctuations begin to dominate the conductance curve. The effective diameter of quantum point constrictions of the devices are estimated to be 30–40 nm. This estimate is based on TEM analysis of test structures and A…
Transport in topological insulators with bulk-surface coupling: Interference corrections and conductance fluctuations
2018
Motivated by the experimental difficulty to produce topological insulators (TIs) of the ${\text{Bi}}_{2}{\text{Se}}_{3}$ family with pure surface-state conduction, we study the effect that the bulk can have on the low-temperature transport properties of gated thin TI films. In particular, we focus on interference corrections, namely weak localization (WL) or weak antilocalization (WAL), and conductance fluctuations (CFs) based on an effective low-energy Hamiltonian. Utilizing diagrammatic perturbation theory, we first analyze the bulk and the surface separately and subsequently discuss WL/WAL and CFs when a tunneling-coupling is introduced. We identify the relevant soft diffusion modes of t…
Nonadiabatic quantum search algorithms
2007
7 pages, 4 figures.-- PACS nrs.: 03.67.Lx, 05.45.Mt, 72.15.Rn.-- ISI Article Identifier: 000251326400049.-- ArXiv pre-print available at: http://arxiv.org/abs/0706.1139
Size dependence of the Josephson critical behavior in pyrolytic graphite TEM lamellae
2014
We have studied the transport characteristics of TEM lamellae of different widths obtained from a graphite sample with electrical contacts at the edges of the embedded interfaces. The temperature dependence of the resistance, as well as the current-voltage characteristics, are compatible with the existence of Josephson-coupled superconducting regions. The transition temperature at which the Josephson behavior sets in decreases with a decreasing interface width and vanishes for widths below 200 nm. This interface-size dependence provides an explanation for differences observed in the transport behavior of graphite-based samples with interfaces, and it appears to be related to the influence o…