Abstract:In the presence of a perpendicular magnetic field, ABC-stacked trilayer graphene's chiral band structure supports a 12-fold degenerate N = 0 Landau level (LL). Along with the valley and spin degrees of freedom, the zeroth LL contains additional quantum numbers associated with the LL orbital index n = 0, 1, 2. Remote inter-layer hopping terms and external potential difference ∆B between the layers lead to LL splitting by introducing a gap ∆LL between the degenerate zeroenergy triplet LL orbitals. Assuming that … Show more
“…Previously, similar linear scaling orbital splitting with Δ ≈ 0.1 meV/T was observed in the lowest LL of the ABC TLG by transport measurements [16]. In the ABC-stacked TLG, the existence of a next-nearest interlayer hopping 4 is expected to lift the orbital degeneracy of the lowest LL and the orbital splitting in magnetic field can be expressed as, is the magnetic length [42]. Therefore, the orbital splitting should increase linearly with magnetic fields.…”
ABC-stacked trilayer graphene (TLG) are predicted to exhibit novel many-body phenomena due to the existence of almost dispersionless flat-band structures near the charge neutrality point (CNP). Here, using high magnetic field scanning tunneling microscopy, we present Landau Level (LL) spectroscopy measurements of high-quality ABC-stacked TLG. We observe an approximately linear magneticfield-scaling of the valley splitting and orbital splitting in the ABC-stacked TLG. Our experiment indicates that the valley splitting decreases dramatically with increasing the LL index. When the lowest LL is partially filled, we find an obvious enhancement of the orbital splitting, attributing to strong many-body effects. Moreover, we observe linear energy scaling of the inverse lifetime of quasiparticles, providing an additional evidence for the strong electron-electron interactions in the ABC-stacked TLG. These results imply that interesting broken-symmetry states and novel electron correlation effects could emerge in the ABC-stacked TLG in the presence of high magnetic fields.
“…Previously, similar linear scaling orbital splitting with Δ ≈ 0.1 meV/T was observed in the lowest LL of the ABC TLG by transport measurements [16]. In the ABC-stacked TLG, the existence of a next-nearest interlayer hopping 4 is expected to lift the orbital degeneracy of the lowest LL and the orbital splitting in magnetic field can be expressed as, is the magnetic length [42]. Therefore, the orbital splitting should increase linearly with magnetic fields.…”
ABC-stacked trilayer graphene (TLG) are predicted to exhibit novel many-body phenomena due to the existence of almost dispersionless flat-band structures near the charge neutrality point (CNP). Here, using high magnetic field scanning tunneling microscopy, we present Landau Level (LL) spectroscopy measurements of high-quality ABC-stacked TLG. We observe an approximately linear magneticfield-scaling of the valley splitting and orbital splitting in the ABC-stacked TLG. Our experiment indicates that the valley splitting decreases dramatically with increasing the LL index. When the lowest LL is partially filled, we find an obvious enhancement of the orbital splitting, attributing to strong many-body effects. Moreover, we observe linear energy scaling of the inverse lifetime of quasiparticles, providing an additional evidence for the strong electron-electron interactions in the ABC-stacked TLG. These results imply that interesting broken-symmetry states and novel electron correlation effects could emerge in the ABC-stacked TLG in the presence of high magnetic fields.
“…As in our previous work, we use the MFT to deal with the interactions between the electrons [10,18]. By the MFT, the 'free energy' functional Φ is approximated as shown in Fig.…”
Section: Mft For Interacting Dirac Fermions In Graphenementioning
We present a formalism to calculate the orbital magnetization of interacting Dirac fermions under a magnetic field. In this approach, the divergence difficulty is overcome with a special limit of the derivative of the thermodynamic potential with respect to the magnetic field. The formalism satisfies the particle-hole symmetry of the Dirac fermions system. We apply the formalism to the interacting Dirac fermions in graphene. The charge and spin orderings and the exchange interactions between all the Landau levels are taken into account by the mean-field theory. The results for the orbital magnetization of interacting Dirac fermions are compared with that of noninteracting cases.PACS numbers: 75.25. Dk,75.70.Ak,73.22.Pr
I. INTRDUCTIONThe study of the properties of interacting Dirac (or Weyl) fermions in (topological) semimetals under a magnetic field is a fundamental subject of the condensed matter physics [1,2]. One of the physical themes is to investigate the orbital magnetization (OM) of the Dirac fermions (DFs) with Coulomb interactions. The OM of an electron system is usually defined as [3]where Ω = Ω(T, µ, B), as a function of the temperature T and the chemical potential µ and the magnetic field B, is the thermal dynamic potential. Equation (1) is equivalent to a statistical average of the OM operator [4]. However, for Dirac (or Weyl) fermions, Eq. (1) is ill defined because the occupation of the Landau levels in the lower band leads to divergence of Ω and thereby M . For noninteracting DFs in graphene, Ω can be evaluated with a special method [5][6][7][8] by which the field B dependent part of Ω is separated out. The effects of finite-temperature occupations and the impurity broadening of the Landau levels on the OM of the noninteracting DFs have been studied [7][8][9]. Nonetheless, for interacting DFs, it is not easy to separate the B-dependent part of Ω from that of the independent part. Study of the OM of Dirac fermions with Coulomb interactions is lacking. How to calculate the OM of interacting DFs is still an open question. In this paper, we are developing a general approach for solving this problem and use it to calculate the OM of interacting Dirac fermions in graphene.
II. FORMALISMThe electrons in graphene are moving on a honeycomb lattice of carbon atoms. The Hamiltonian of the electrons with a neutralizing background iswhere c † is (c is ) creates (annihilates) an electron of spin s in site i, ij sums over the nearest-neighbor (NN) sites, t ≈ 3 eV is the NN hopping energy, δn is = n is − n s is the number deviation of electrons of spin s at site i from the average occupation n s , and U and v ij are the Coulomb interactions between electrons. In real space, v ij = v(r ij ) with r ij the distance between sites i and j is given bywhere q 0 is a parameter taking into account the wavefunction spreading effect in the short-range interactions between electrons. Here we take q 0 = 0.5/a 0 with a 0 ≈ 2.46 A as the lattice constant of graphene. For carrier concentration close to the charge neutrality...
“…In order to treat the single-layer, bilayer graphene [34] and chiral multilayer graphene (neglecting the trigonal warping effects) with 2 N layers [35][36][37][38] simultaneously we start from the Hamiltonian given in a unified form as …”
Section: Exact Calculation Of Dos and Capacitance In Chiral Multilayementioning
We present an overview of our recent results on quantum magnetic oscillations in new functional materials. We begin with the Lifshitz and Kosevich approach for quasi-2D layered materials and obtain general formulas for the oscillatory parts of the grand thermodynamic potential and magnetization. Then we consider the oscillations of the Nernst-Ettingshausen coefficient which consists of thermal and magnetization parts. The difference between normal and Dirac carriers is also discussed. To conclude we consider a model for multilayer graphene which allows to calculate exactly the Berry phase which remains undetermined in the Lifshitz-Kosevich approach. The magnetic oscillations of the density of states and capacitance for different number of the carbon layers are described.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.