Dependence of quantum-Hall conductance on the edge-state equilibration position in a bipolar graphene sheet

Ki, Dong–Keun; Nam, Seung‐Geol; Lee, Hu-Jong; Özyilmaz, Barbaros

doi:10.1103/physrevb.81.033301

Cited by 26 publications

(35 citation statements)

References 16 publications

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“…Graphene p−n junctions have already displayed new and exciting phenomena such as Klein tunneling, where electrons traveling perpendicular to the junction experience zero resistance,144 fractional quantum Hall transport,145 and Veselago lensing, where diverging electron waves are refocused by the junction 146. Therefore, great efforts have been made to fabricate graphene p‐n junctions including multiple electrostatic gates,145, 147 chemical treatment by gas exposure,117 polymer‐induced doping,113, 148, 149 and electronic modification of the substrates 150. In the previous section, we have demonstrated the use of SAMs on SiO 2 substrates to control the charge accumulation at the dielectric/graphene interface, resulting p‐doping or n‐doping of graphene.…”

Section: Sams As Auxiliary Layers Carbon Nanomaterials As Active mentioning

confidence: 99%

Unique Role of Self‐Assembled Monolayers in Carbon Nanomaterial‐Based Field‐Effect Transistors

Chen

Guo

2013

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Molecular self-assembly is a promising technology for creating reliable functional films in optoelectronic devices with full control of thickness and even spatial resolution. In particular, rationally designed self-assembled monolayers (SAMs) play an important role in modifying the electrode/semiconductor and semiconductor/dielectric interfaces in field-effect transistors. Carbon nanomaterials, especially single-walled carbon nanotubes and graphene, have attracted intense interest in recent years due to their remarkable physicochemical properties. The combination of the advantages of both SAMs and carbon nanomaterials has been opening up a thriving research field. In this Review article, the unique role of SAMs acting as either active or auxiliary layers in carbon nanomaterials-based field-effect transistors is highlighted for tuning the substrate effect, controlling the carrier type and density in the conducting channel, and even installing new functionalities. The combination of molecular self-assembly and molecular engineering with materials fabrication could incorporate diverse molecular functionalities into electrical nanocircuits, thus speeding the development of nanometer/molecular electronics in the future.

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Section: Sams As Auxiliary Layers Carbon Nanomaterials As Active mentioning

confidence: 99%

Unique Role of Self‐Assembled Monolayers in Carbon Nanomaterial‐Based Field‐Effect Transistors

Chen

Guo

2013

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“…7 One way to gain a better insight on the properties of these systems are multiterminal magnetotransport experiments, which can be used to study the equilibrium of the edge states at the junction. 8 Due to its bipolar nature, graphene offers the unique possibility to study the interaction of electron and hole edge states in a two-dimensional (2D) system.…”

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confidence: 99%

“…2(b)] channels being present in both regions travel across the sample, while the additional ones due to a higher carrier density and therefore filling factor ν = nh/eB circulate in only one region. This leads to different longitudinal resistances which are described by the Landauer-Büttiker formalism as fractions of the von Klitzing constant R K : 8,18,19 …”

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Mixing of edge states at a bipolar graphene junction

et al. 2013

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An Atomic Force Microscope is used to locally manipulate a single layer graphene sheet. Transport measurements in this region as well as in the unmanipulated part reveal different charge carrier densities while mobilities stay in the order of 10 4 cm 2 (Vs) −1 . With a global backgate, the system is tuned from a unipolar n-n' or p-p' junction with different densities to a bipolar p-n junction. Magnetotransport across this junction verifies its nature, showing the expected quantized resistance values as well as the switching with the polarity of the magnetic field. The mixing of edge states at the p-n junction is shown to be supressed at high magnetic fields.

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“…(2) would no longer be valid. Instead, it would be replaced by R = 1/G with In contrast to edge state mixing experiments in GaAs QWs [27,28] or graphene [2,7,31,32], our system is made up of two distinct constituent parts, and the electron and hole LL spectra differ vastly: m GaSb /m InAs ≈ 10 [35]. The electron and hole states are also spatially separated in the growth direction of the heterostructure.…”

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confidence: 99%

Lateral p−n Junction in an Inverted InAs/GaSb Double Quantum Well

et al. 2017

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We present transport measurements on a lateral p-n junction in an inverted InAs/GaSb double quantum well at zero and nonzero perpendicular magnetic fields. At a zero magnetic field, the junction exhibits diodelike behavior in accordance with the presence of a hybridization gap. With an increasing magnetic field, we explore the quantum Hall regime where spin-polarized edge states with the same chirality are either reflected or transmitted at the junction, whereas those of opposite chirality undergo a mixing process, leading to full equilibration along the width of the junction independent of spin. These results lay the foundations for using p-n junctions in InAs/GaSb double quantum wells to probe the transition between the topological quantum spin Hall and quantum Hall states.Diodes based on p-n junctions are one of the basic building blocks of electronic systems, with a multitude of applications including rectification, switching, signal generation and amplification, light emission, as well as photovoltaics. Advances in materials research in recent years have produced p-n junctions in a variety of novel systems such as graphene [1,2] and transition-metal dichalcogenides [3,4], an emerging class of two-dimensional semiconductors [5,6]. Beyond practical accomplishments such as downscaling, these junctions also allow us to gain new insights into fundamental physical phenomena, for example, how electron and hole edge states interact with each other in the quantum Hall (QH) regime [2,7].Here, we study the formation of a lateral p-n junction using local top gating in an inverted InAs/GaSb double quantum well (QW) heterostructure, a semiconductor system that naturally hosts both electrons and holes that are spatially separated in the vertical (growth) direction. Depending on the thicknesses of the InAs and GaSb layers, it intrinsically possesses inverted or noninverted band alignment. Furthermore, the band alignment is affected by both electric and magnetic fields, allowing for continuous tuning between the two phases [8][9][10]. In the inverted phase, coupling between the bands leads to the opening of a hybridization gap [11][12][13] hosting topologically protected helical edge states, making InAs/GaSb double QWs a two-dimensional topological insulator (TI) or quantum spin Hall (QSH) insulator [14][15][16][17][18]. Apart from the TI properties of the system, it is also of more general interest due to its complex band structure [19,20], strong spin-orbit interaction (SOI) [21][22][23], and optical properties [24].A pair of overlapping top gates enables us to independently control carrier type and density in two adjacent parts of the sample at a zero magnetic field and in the QH regime. At a zero field and when the two parts are populated by charge carriers of opposite polarity, the electrons and holes situated in their respective QWs are separated in energy by the hybridization gap responsible for the QSH insulator properties of these QWs. This gap allows the junction to function as a diode in the appropriate regimes, ...

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Dependence of quantum-Hall conductance on the edge-state equilibration position in a bipolar graphene sheet

Cited by 26 publications

References 16 publications

Unique Role of Self‐Assembled Monolayers in Carbon Nanomaterial‐Based Field‐Effect Transistors

Unique Role of Self‐Assembled Monolayers in Carbon Nanomaterial‐Based Field‐Effect Transistors

Mixing of edge states at a bipolar graphene junction

Lateral p−n Junction in an Inverted InAs/GaSb Double Quantum Well

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