Imaging Dirac fermions flow through a circular Veselago lens

Brun, Boris; Moreau, Nicolas; Somanchi, Sowmya; Nguyễn, Việt Hùng; Watanabe, Kenji; Taniguchi, Takashi; Charlier, Jean Christophe; Stampfer, Christoph; Hackens, Benoît

doi:10.1103/physrevb.100.041401

Cited by 46 publications

(46 citation statements)

References 51 publications

(39 reference statements)

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“…Since |r τ,s | 2 = 1 ∀E, the incoming wave is perfectly reflected at the boundary, regardless of τ and s. Inserting the full wave function (9) with (17) and n D (x = 0) ≡ e x into equation 8, we find Γ τ = τ . Clearly the whole scattering problem can be rotated by any angle ϑ, i.e., for the α − T 3 lattice the IMBC at ∂D becomes:…”

Section: Infinite Mass Boundary Conditionmentioning

confidence: 95%

“…One of the options is nanoscale top gates that modify the electronic structure in a restricted area [10]. This allows to imprint junctions and barriers relatively easy, and therefore opens new possibilities to study fascinating phenomena such as Klein tunnelling [11,12], Zitterbewegung [13,14], particle confinement [15,16], Veselago lensing [17], Mie scattering analogues [18][19][20][21][22] and resonant scattering [23,24]. Clearly the energy of the charge-carrier states can be manipulated by (perpendicular) magnetic fields as well.…”

Section: Introductionmentioning

confidence: 99%

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Electronic properties of α − 𝒯3 quantum dots in magnetic fields

Filusch

Fehske

2020

Eur. Phys. J. B

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We address the electronic properties of quantum dots in the two-dimensional α − 𝒯3 lattice when subjected to a perpendicular magnetic field. Implementing an infinite mass boundary condition, we first solve the eigenvalue problem for an isolated quantum dot in the low-energy, long-wavelength approximation where the system is described by an effective Dirac-like Hamiltonian that interpolates between the graphene (pseudospin 1/2) and Dice (pseudospin 1) limits. Results are compared to a full numerical (finite-mass) tight-binding lattice calculation. In a second step we analyse charge transport through a contacted α − 𝒯3 quantum dot in a magnetic field by calculating the local density of states and the conductance within the kernel polynomial and Landauer-Büttiker approaches. Thereby the influence of a disordered environment is discussed as well. Graphical abstract

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Section: Infinite Mass Boundary Conditionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Electronic properties of α − 𝒯3 quantum dots in magnetic fields

Filusch

Fehske

2020

Eur. Phys. J. B

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“…To show the formation of interference pattern of anisotropic and tilted MDFs across the PNJ, we examine the classical trajectory determined by the phase accumulation j np (see equation (17)). The classical trajectory with specific k y,c is determined by Noting here, equation (21) has no dependence on j, so it has the same form for two special junctions with f=±π/2. And equation ( and the arbitrary order derivativeof propagation phase j j np on the classical trajectory also vanishes identical to the case for isotropic MDFs in graphene [37].…”

Section: F=±π/2: Veselago Focusing and Normal Causticsmentioning

confidence: 99%

Anomalous caustics and Veselago focusing in 8-Pmmn borophene p–n junctions with arbitrary junction directions

Zhang

Yang

2019

New J. Phys.

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Negative refraction usually demands complex structure engineering while it is very natural for massless Dirac fermions (MDFs) across the p-n junction (PNJ), this leads to Dirac electron optics. The emergent Dirac materials may exhibit hitherto unidentified phenomenon due to their nontrivial band structures in contrast to the isotropic MDFs in graphene. Here, as a specific example, we explore the negative refraction induced caustics and Veselago focusing of tilted MDFs across 8-Pmmn borophene PNJs. To this aim, we develop a technique to effectively construct the electronic Green's function (GF) in PNJs with arbitrary junction directions. Based on analytical discussions and numerical calculations, we demonstrate the strong dependence of interference pattern on the junction direction. As the junction direction perpendicular to the tilt direction, Veselago focusing or normal caustics (similar to that in graphene) appears resting on the doping configuration of the PNJs, otherwise anomalous caustics (different from that in graphene) occurs which is manipulated by the junction direction and the doping configuration. Finally, the developed GF technique is generally promising to uncover the unique transport of emergent MDFs, and the discovered anomalous caustics makes tilted MDFs potential applications in Dirac electron optics.

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“…Beyond these CR-related perspectives, I would find it highly interesting to examine DFO devices with imaging techniques like scanning gate microscopy [206,211,212], a single electron transistor on an AFM tip [213] or NV centers in diamonds [214]. This could lead to a direct observation of the refraction/reflection effects and at the same time remove doubts about the domains of validity of the non-interacting DFO picture.…”

Section: Discussionmentioning

confidence: 99%

“…Dirac fermion optics has also been explored beyond the pure transport approach, e.g. by combining transport with scanning gate microscopy to probe a DFO lens [206] or with scanning tunneling microscopy and spectroscopy to characterize the local doping profile of graphene p-n junctions at the atomic scale [128].…”

Section: Other Dfo Studiesmentioning

confidence: 99%

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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Imaging Dirac fermions flow through a circular Veselago lens

Cited by 46 publications

References 51 publications

Electronic properties of α − 𝒯3 quantum dots in magnetic fields

Electronic properties of α − 𝒯3 quantum dots in magnetic fields

Anomalous caustics and Veselago focusing in 8-Pmmn borophene p–n junctions with arbitrary junction directions

Dirac fermion optics and plasmonics in graphene microwave devices

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