scholarly journals Counter-propagating charge transport in the quantum Hall effect regime

Science ◽  
2019 ◽  
Vol 363 (6422) ◽  
pp. 54-57 ◽  
Author(s):  
Fabien Lafont ◽  
Amir Rosenblatt ◽  
Moty Heiblum ◽  
Vladimir Umansky
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Electron Gas ◽  
Quantum Hall ◽  
Charge Carriers ◽  
Perpendicular Magnetic Field ◽  
Quantum Hall Regime ◽  
Hall Regime ◽  
Spin Polarized ◽  
Conjugate States

The quantum Hall effect, observed in a two-dimensional (2D) electron gas subjected to a perpendicular magnetic field, imposes a 1D-like chiral, downstream, transport of charge carriers along the sample edges. Although this picture remains valid for electrons and Laughlin’s fractional quasiparticles, it no longer holds for quasiparticles in the so-called hole-conjugate states. These states are expected, when disorder and interactions are weak, to harbor upstream charge modes. However, so far, charge currents were observed to flow exclusively downstream in the quantum Hall regime. Studying the canonical spin-polarized and spin-unpolarized v = 2/3 hole-like states in GaAs-AlGaAs heterostructures, we observed a significant upstream charge current at short propagation distances in the spin unpolarized state.

scholarly journals Upstream modes and antidots poison graphene quantum Hall effect

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
N. Moreau ◽  
B. Brun ◽  
S. Somanchi ◽  
K. Watanabe ◽  
T. Taniguchi ◽  
...  
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
High Mobility ◽  
Charge Carriers ◽  
Remarkable Property ◽  
One Dimensional ◽  
Quantum Hall Regime ◽  
Hall Regime ◽  
Scanning Gate

AbstractThe quantum Hall effect is the seminal example of topological protection, as charge carriers are transmitted through one-dimensional edge channels where backscattering is prohibited. Graphene has made its marks as an exceptional platform to reveal new facets of this remarkable property. However, in conventional Hall bar geometries, topological protection of graphene edge channels is found regrettably less robust than in high mobility semi-conductors. Here, we explore graphene quantum Hall regime at the local scale, using a scanning gate microscope. We reveal the detrimental influence of antidots along the graphene edges, mediating backscattering towards upstream edge channels, hence triggering topological breakdown. Combined with simulations, our experimental results provide further insights into graphene quantum Hall channels vulnerability. In turn, this may ease future developments towards precise manipulation of topologically protected edge channels hosted in various types of two-dimensional crystals.

scholarly journals FIELD THEORY OF ANISOTROPIC QUANTUM HALL GAS: METROLOGY AND A NOVEL QUANTUM HALL REGIME

2003 ◽  
Vol 17 (27) ◽  
pp. 4765-4818 ◽  
Author(s):  
K. ISHIKAWA ◽  
T. AOYAMA ◽  
Y. ISHIZUKA ◽  
N. MAEDA
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Hall Conductance ◽  
Von Neumann ◽  
Integer Quantum Hall Effect ◽  
Quantum Hall Regime ◽  
Realistic Situation ◽  
Hall Regime ◽  
Integer Quantum

The von Neumann lattice representation is a convenient representation for studying several intriguing physics of quantum Hall systems. In this formalism, electrons are mapped to lattice fermions. A topological invariant expression of the Hall conductance is derived and is used for the proof of the integer quantum Hall effect in the realistic situation. Anisotropic quantum Hall gas is investigated based on the Hartree–Fock approximation in the same formalism. Thermodynamic properties, transport properties, and unusual response under external modulations are found. Implications for the integer quantum Hall effect in the finite systems are also studied and a new quantum Hall regime with non-zero longitudinal resistance is shown to exist.

scholarly journals An all-epitaxial nitride heterostructure with concurrent quantum Hall effect and superconductivity

2021 ◽  
Vol 7 (8) ◽  
pp. eabf1388
Author(s):  
Phillip Dang ◽  
Guru Khalsa ◽  
Celesta S. Chang ◽  
D. Scott Katzer ◽  
Neeraj Nepal ◽  
...  
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Electron Gas ◽  
Quantum Hall ◽  
High Electron Mobility Transistor ◽  
High Electron ◽  
2D Electron Gas ◽  
Integer Quantum Hall Effect ◽  
Topological Quantum ◽  
Integer Quantum

Creating seamless heterostructures that exhibit the quantum Hall effect and superconductivity is highly desirable for future electronics based on topological quantum computing. However, the two topologically robust electronic phases are typically incompatible owing to conflicting magnetic field requirements. Combined advances in the epitaxial growth of a nitride superconductor with a high critical temperature and a subsequent nitride semiconductor heterostructure of metal polarity enable the observation of clean integer quantum Hall effect in the polarization-induced two-dimensional (2D) electron gas of the high-electron mobility transistor. Through individual magnetotransport measurements of the spatially separated GaN 2D electron gas and superconducting NbN layers, we find a small window of magnetic fields and temperatures in which the epitaxial layers retain their respective quantum Hall and superconducting properties. Its analysis indicates that in epitaxial nitride superconductor/semiconductor heterostructures, this window can be significantly expanded, creating an industrially viable platform for robust quantum devices that exploit topologically protected transport.

scholarly journals Quantum parity Hall effect in Bernal-stacked trilayer graphene

2019 ◽  
Vol 116 (21) ◽  
pp. 10286-10290 ◽  
Author(s):  
Petr Stepanov ◽  
Yafis Barlas ◽  
Shi Che ◽  
Kevin Myhro ◽  
Greyson Voigt ◽  
...  
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Exchange Interactions ◽  
Mirror Reflection ◽  
Edge States ◽  
State Variables ◽  
Coulomb Interactions ◽  
Spin Polarized ◽  
Trilayer Graphene

The quantum Hall effect has recently been generalized from transport of conserved charges to include transport of other approximately conserved-state variables, including spin and valley, via spin- or valley-polarized boundary states with different chiralities. Here, we report a class of quantum Hall effect in Bernal- or ABA-stacked trilayer graphene (TLG), the quantum parity Hall (QPH) effect, in which boundary channels are distinguished by even or odd parity under the system’s mirror reflection symmetry. At the charge neutrality point, the longitudinal conductance σxx is first quantized to 4e2/h at a small perpendicular magnetic field B⊥, establishing the presence of four edge channels. As B⊥ increases, σxx first decreases to 2e2/h, indicating spin-polarized counterpropagating edge states, and then, to approximately zero. These behaviors arise from level crossings between even- and odd-parity bulk Landau levels driven by exchange interactions with the underlying Fermi sea, which favor an ordinary insulator ground state in the strong B⊥ limit and a spin-polarized state at intermediate fields. The transitions between spin-polarized and -unpolarized states can be tuned by varying Zeeman energy. Our findings demonstrate a topological phase that is protected by a gate-controllable symmetry and sensitive to Coulomb interactions.

scholarly journals Partially spin-polarized quantum Hall effect in the filling factor range1/3<ν<2/5

2003 ◽  
Vol 67 (12) ◽  
Author(s):  
Chia-Chen Chang ◽  
Sudhansu S. Mandal ◽  
Jainendra K. Jain
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Filling Factor ◽  
Quantum Hall ◽  
Spin Polarized

Interaction of magnetoexcitons and two-dimensional electron gas in the quantum Hall regime

1990 ◽  
Vol 64 (20) ◽  
pp. 2434-2437 ◽  
Author(s):  
W. Chen ◽  
M. Fritze ◽  
A. V. Nurmikko ◽  
D. Ackley ◽  
C. Colvard ◽  
...  
Keyword(s):  
Electron Gas ◽  
Quantum Hall ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Quantum Hall Regime ◽  
Hall Regime ◽  
Dimensional Electron Gas

Can fractional quantum Hall effect be due to the formation of coherent wave structures in a 2D electron gas?

2016 ◽  
Vol 30 (13) ◽  
pp. 1650142
Author(s):  
Babur M. Mirza
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Electron Gas ◽  
Density Wave ◽  
Quantum Hall ◽  
Microscopic Theory ◽  
Fractional Quantum Hall Effect ◽  
Hall Resistance ◽  
Fractional Quantum ◽  
Fractional Quantum Hall

A microscopic theory of integer and fractional quantum Hall effects is presented here. In quantum density wave representation of charged particles, it is shown that, in a two-dimensional electron gas coherent structures form under the low temperature and high density conditions. With a sufficiently high applied magnetic field, the combined [Formula: see text] particle quantum density wave exhibits collective periodic oscillations. As a result the corresponding quantum Hall voltage function shows a step-wise change in multiples of the ratio [Formula: see text]. At lower temperatures further subdivisions emerge in the Hall resistance, exhibiting the fractional quantum Hall effect.

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