Gyrotropic Zener tunneling and nonlinear IV curves in the zero-energy Landau level of graphene in a strong magnetic field

Laitinen, Antti; Kumar, Manohar; Hakonen, Pertti; Sonin, É. B.

doi:10.1038/s41598-017-18959-7

Cited by 7 publications

(10 citation statements)

References 40 publications

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“…The discrepancy could be due to an overestimation of L c by the classical-shear-modulus model where the renormalization of the traverse phonon dispersion relation by quantum effects has been ignored, although this is disputable at very low charge density and in high magnetic field 38 . Additionally, in thermally activated transport near the threshold voltage, the Lorentz force will become comparable to the electric field and hence, the so-called gyrotropic tunneling of quasiparticles 39 will influence the sliding of the Wigner crystal. For example, by using a 45° sliding angle w.r.t.…”

Section: Resultsmentioning

confidence: 99%

Unconventional fractional quantum Hall states and Wigner crystallization in suspended Corbino graphene

2018

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Competition between liquid and solid states in two-dimensional electron systems is an intriguing problem in condensed matter physics. We have investigated competing Wigner crystal and fractional quantum Hall (FQH) liquid phases in atomically thin suspended graphene devices in Corbino geometry. Low-temperature magnetoconductance and transconductance measurements along with IV characteristics all indicate strong charge density dependent modulation of electron transport. Our results show unconventional FQH phases which do not fit the standard Jain’s series for conventional FQH states, instead they appear to originate from residual interactions of composite fermions in partially filled Landau levels. Also at very low charge density with filling factors , electrons crystallize into an ordered Wigner solid which eventually transforms into an incompressible Hall liquid at filling factors around ν ≤ 1/7. Building on the unique Corbino sample structure, our experiments pave the way for enhanced understanding of the ordered phases of interacting electrons.

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Section: Resultsmentioning

confidence: 99%

Unconventional fractional quantum Hall states and Wigner crystallization in suspended Corbino graphene

2018

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“…Specific features of gapless graphene, which can be seen in the N = 0 state at charge neutrality, are disregarded in this work. They have been investigated recently in single layer graphene [24], where breakdown was interpreted in terms of a gyrotropic Zener tunneling effect [23].…”

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confidence: 99%

Landau Velocity for Collective Quantum Hall Breakdown in Bilayer Graphene

Yang

Graef

et al. 2018

Phys. Rev. Lett.

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1 Breakdown of the quantum Hall effect (QHE) is commonly associated with an electric field approaching the inter Landau-level (LL) Zener field, ratio of the Landau gap and cyclotron radius. Eluded in semiconducting heterostructures, in spite of extensive investigation, the intrinsic Zener limit is reported here using high-mobility bilayer graphene and high-frequency current noise. We show that collective excitations arising from electron-electron interactions are essential. Beyond a noiseless ballistic QHE regime a large superpoissonian shot noise signals the breakdown via inter-LL scattering. The breakdown is ultimately limited by collective excitations in a regime where phonon and impurity scattering are quenched. The breakdown mechanism can be described by a Landau critical velocity as it bears strong similarities with the roton mechanism of superfluids.The Fermi sea of a 2D electronic system is unstable at high magnetic field (B-field) toward the formation of discrete Landau levels, giving rise to the quantum Hall effect (QHE) [1], where the bulk is a Landau insulator. The QHE has led to many developments in physics, including recent ones in metrology [2,3] and quantum electronics [4]. The fate of the QHE at high electric field (E-field) remains an open question, as well as the nature of the phase reached when the drift velocity v d = E × B/B 2 approaches the cyclotron velocity R c ω c , where R c and ω c are the cyclotron radius and frequency, resulting in cyclotron orbit breaking. A precursor of the transition is the quantum Hall breakdown reported soon after the discovery of QHE [5-7]. The breakdown field E bd marks the onset of longitudinal resistance and dissipation. Its natural scale is the Zener field, E c ∼hω c /eR c , with ω c =eB/m * and R c ∼ √ Nl B , where m * is the effective mass, N the number of occupied LLs and l B = h/eB the magnetic length [8]. The relevance of the Zener mechanism was soon questioned as E c exceeds experimental E bd . Besides, genuine inter-LL tunneling suffers from a strong momentum mismatch at finite doping, ∆q = 2k F where k F = √ 2N/l B is the Fermi momentum [9]. It can be circumvented assuming impurity-assisted or phonon-mediated quasi-elastic inter LL scattering (QUILLS) [8,10]. Breakdown was extensively investigated in semiconductors [6,7,11-16] and graphene [17-20], but mainly in Hall bars. Few experiments used constrictions [7,11], or Corbino geometries [21-24], with the purpose of achieving homogeneous current, or E-field, distributions. In all cases breakdown E-fields are smaller than Zener fields, and critical Hall current densities J < ∼ 50 A/m [18]. The leading explanation thus shifted to a thermal instability, driven 2 by the imbalance between dissipation and phonon relaxation [25]; its threshold is materialdependent and lower than E c [17,18,26,27]. According to low-frequency noise measurements, the thermal instability eventually gives rise to electron avalanches [11,21,22]. On comparing breakdown (v bd = J bd /ne) and Zener (v c = E c /B) velocities one ...

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“…At B = 7 T, closer to the other works mentioned above, the authors report a breakdown current density of 4 A/m. Still, we can translate the record current density 43 A/m to a record breakdown field E c = j c h/νe 2 ≈ 5 × 10 5 V/m, which -so far -only compares to the breakdown fields ∼ 10 5 V/m observed for the ν = 0 scenario by Laitinen et al [289] in suspended graphene.…”

Section: Summary Of Experiments: From 2deg To Graphenementioning

confidence: 65%

“…5.7d) that can potentially operate up to room temperature [286]. There have been a few studies of the breakdown both in exfoliated [283,286,287], epitaxial (grown on SiC) [272,282,288], suspended [289,290] and hBN-encapsulated [291] single-and bilayer graphene. The chosen geometry was typically a Hall bar, except for refs.…”

Section: Summary Of Experiments: From 2deg To Graphenementioning

confidence: 99%

“…The chosen geometry was typically a Hall bar, except for refs. [289,290], where Corbino disks were investigated. The carrier mobilities for most of the devices (except the suspended and encapsulated ones) was on the order of 5000 − 10000 cm 2 /Vs and breakdown current densities were typically on the order of 1 − 5 A/m at temperatures around 0.3 − 2 K. In most of these works, the breakdown was characterized around B = 9 − 10 T and the filling factor ν = 2.…”

Section: Summary Of Experiments: From 2deg To Graphenementioning

confidence: 99%

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Dirac fermion optics and plasmonics in graphene microwave devices

Graef

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This thesis addresses the physics of non-interacting and interacting Dirac fermions in ballistic graphene. Three main phenomena are investigated: Dirac fermion optics in electronic prisms defined by p-n junctions, GHz plasmonics in plasma resonance capacitors, and the breakdown of the integer quantum Hall effect (QHBD) by a magnetoexciton instability. Our technology relies on h-BN encapsulated graphene devices characterized by DC to GHz electronic transport and noise.We first study the total internal reflection of electrons in a gate-defined corner reflector. Both geometric and coherent electron optics effects are demonstrated and the device is shown to be sensitive to minute phonon scattering rates. It is then used as a proof-of-concept for GHz electron optics experiments in graphene.We introduce top-gated graphene field-effect capacitors as a platform to study ultralong wavelength plasmons characterized with a vector network analyzer. We simultaneously measure resistivity, capacitance and kinetic inductance. We observe a resonance at 40 GHz with a quality factor of two, corresponding to a plasmon of 100 µm wavelength. This result sets a milestone for the realization of resonant plasmonic devices.We finally move our attention to the QHBD in a bilayer graphene sample. DC transport and GHz noise measurements show that the elusive intrinsic breakdown field can be reached in graphene. Its signature is an abrupt increase of noise, with a super-Poissonian Fano factor. We propose a magnetoexciton instability scenario as the origin of breakdown.These results show how progress in sample fabrication has enabled us to study new classes of ballistic devices, to explore new fundamental phenomena and to envision more complex experiments like: time-of-flight measurements of acoustic phonons, characterization of plasmon propagation in bipolar superlattices, or breakdown in single layer graphene. In terms of applications, this thesis paves the way for room-temperature electron optics devices, plasma-resonance-based THz detectors, and improvement of quantum Hall resistance standards.

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Gyrotropic Zener tunneling and nonlinear IV curves in the zero-energy Landau level of graphene in a strong magnetic field

Cited by 7 publications

References 40 publications

Unconventional fractional quantum Hall states and Wigner crystallization in suspended Corbino graphene

Unconventional fractional quantum Hall states and Wigner crystallization in suspended Corbino graphene

Landau Velocity for Collective Quantum Hall Breakdown in Bilayer Graphene

Dirac fermion optics and plasmonics in graphene microwave devices

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