Fabrication of graphene p-n-p junctions with contactless top gates

Liu, Gang; Velasco, Jairo; Bao, Wenzhong; Lau, Chun Ning

doi:10.1063/1.2928234

Cited by 137 publications

(147 citation statements)

References 25 publications

Supporting

Mentioning

143

Contrasting

Order By: Relevance

“…This feature has been agreed in recent experiments for pn and pnp junctions in MLG. 40,57,58,[60][61][62][63][64] The difference of the conductance, or equivalently the resistance, between the nn and np (or between pp and pn) in experiments is even more obvious possibly due to the smooth interface that leads to an exponentially decaying form of T , 24 as we have reviewed and discussed in Sec. III A 2.…”

Section: B Klein Tunneling In Mlgmentioning

confidence: 99%

Spin-dependent Klein tunneling in graphene: Role of Rashba spin-orbit coupling

2012

View full text Add to dashboard Cite

Within an effective Dirac theory the low-energy dispersions of monolayer graphene in the presence of Rashba spin-orbit coupling and spin-degenerate bilayer graphene are described by formally identical expressions. We explore implications of this correspondence for transport by choosing chiral tunneling through pn and pnp junctions as a concrete example. A real-space Green's function formalism based on a tight-binding model is adopted to perform the ballistic transport calculations, which cover and confirm previous theoretical results based on the Dirac theory. Chiral tunneling in monolayer graphene in the presence of Rashba coupling is shown to indeed behave like in bilayer graphene. Combined effects of a forbidden normal transmission and spin separation are observed within the single-band n ↔ p transmission regime. The former comes from real-spin conservation, in analogy with pseudospin conservation in bilayer graphene, while the latter arises from the intrinsic spin-Hall mechanism of the Rashba coupling.

show abstract

Section: B Klein Tunneling In Mlgmentioning

confidence: 99%

Spin-dependent Klein tunneling in graphene: Role of Rashba spin-orbit coupling

2012

View full text Add to dashboard Cite

show abstract

“…At constant B, we observe an intriguing "hexagon" patterns in G( ! ,ν) phase diagram, which arises from crossings between symmetry-broken LLs.Dual-gated suspended devices are fabricated using a multi-level lithography technique 41,42 (Fig. 1b).…”

mentioning

confidence: 99%

“…Dual-gated suspended devices are fabricated using a multi-level lithography technique 41,42 (Fig. 1b).…”

mentioning

confidence: 99%

Multicomponent Quantum Hall Ferromagnetism and Landau Level Crossing in Rhombohedral Trilayer Graphene

et al. 2015

View full text Add to dashboard Cite

Using transport measurements, we investigate multicomponent quantum Hall (QH) ferromagnetism in dual-gated rhombohedral trilayer graphene (r-TLG), in which the real spin, orbital pseudospin and layer pseudospins of the lowest Landau level form spontaneous ordering. We observe intermediate quantum Hall plateaus, indicating a complete lifting of the degeneracy of the zeroth Landau level (LL) in the hole-doped regime. In charge neutral r-TLG, the orbital degeneracy is broken first, and the layer degeneracy is broken last and only the in presence of an interlayer potential U⊥. In the phase space of U⊥ and filling factor ν, we observe an intriguing "hexagon" pattern, which is accounted for by a model based on crossings between symmetry-broken LLs.Keywords: quantum Hall ferromagnetism, graphene, trilayer, rhombohedral stacking, Landau level crossing * Emails: kenosis101@gmail.com, yafisb@gmail.com; lau@physics.ucr.edu In the quantum Hall (QH) regime, when the energies of two or more Landau levels (LLs) are brought to alignment, the spinor language is often used to describe the different degrees of freedom, such as layer and orbital pseudospins, due to their close analogy to the spins in a twodimensional ferromagnet. When these LLs are less than completely full, competition between these degrees of freedom leads to formation of electronic states with spontaneous ordering of pseudospins, much like the spontaneous real spin alignment in a ferromagnet. For this reason, these symmetry-broken QH states are called QH ferromagnets, with real or pseudo-spin orderings that maybe easy-plane, i.e. akin to a XY Heisenberg magnet, or easy-axis, i.e. akin to an Ising ferromagnet. These QH ferromagnetic states provide a rich platform for investigation of the competition among different symmetries, as well as providing insight into the itinerant magnetism in standard magnets.The recent emergence of two-dimensional (2D) graphene provides new playground for multicomponent QH ferromagnetic states and the associated phase transitions 1-6 7-19 20-28 . With the advent of high mobility samples that may be either suspended 29,30 or supported on BN substrates 31,32 , and advanced device geometry such as dual-gates or split top gates [33][34][35] , few-layer graphene provides QH systems with unusual symmetries and unprecedented tunability.In particular, rhombohedral trilayer graphene is such a QH system with very flat bands near the charge neutrality point. Its LL energies are given bywhere N is an integer denoting the LL index, e the electron charge, v F~1 0 6 m/s the Fermi velocity of single layer graphene, γ 1~0 .3 eV the interlayer hopping energy, and h Planck's constant. The degeneracy between the N=0, 1 and 2 LLs, together with the spin and valley degrees of freedom, yield the 12-fold degeneracy of the lowest LL, and give rise to plateaus at filling factors ν=±6, ±10, ±14… Interactions and/or single particle effects lift this 12-fold degeneracy, leading to incompressible QH ferromagnetic states at intermediate fillings 36,37 , with ex...

show abstract

“…The Ti/Al electrodes and Ti suspended top gates 17,18 are fabricated by electron beam lithography. A device schematic is shown in Fig.…”

mentioning

confidence: 99%

Quantum Transport and Field-Induced Insulating States in Bilayer Graphene pnp Junctions

et al. 2010

Self Cite

View full text Add to dashboard Cite

We perform transport measurements in high quality bilayer graphene pnp junctions with suspended top gates. At a magnetic field B=0, we demonstrate band gap opening by an applied perpendicular electric field, with an On/Off ratio up to 20,000 at 260mK. Within the band gap, the conductance decreases exponentially by 3 orders of magnitude with increasing electric field, and can be accounted for by variable range hopping with a gate-tunable density of states, effective mass, and localization length. At large B, we observe quantum Hall conductance with fractional values, which arise from equilibration of edge states between differentially-doped regions, and the presence of an insulating state at filling factor ν=0. Our work underscores the importance of bilayer graphene for both fundamental interest and technological applications.

show abstract

Fabrication of graphene p-n-p junctions with contactless top gates

Cited by 137 publications

References 25 publications

Spin-dependent Klein tunneling in graphene: Role of Rashba spin-orbit coupling

Spin-dependent Klein tunneling in graphene: Role of Rashba spin-orbit coupling

Multicomponent Quantum Hall Ferromagnetism and Landau Level Crossing in Rhombohedral Trilayer Graphene

Quantum Transport and Field-Induced Insulating States in Bilayer Graphene pnp Junctions

Contact Info

Product

Resources

About