Scanning tunneling spectroscopy study of the Dirac spectrum of germanene

Walhout, C.J.; Acun, Adil; Zhang, Lijie; Ezawa, Motohiko; Zandvliet, Henricus J.W.

doi:10.1088/0953-8984/28/28/284006

Cited by 19 publications

(22 citation statements)

References 28 publications

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“…Experimentally determined linear V-shaped density-of-states (DoS) provides strong verification for a gapped Dirac dispersion relation in germanene. 9 The Hamiltonians used to model these buckled-lattice systems need to take into account the effect of SOC and interlayer atomic interactions. While graphene and silicene are two representatives of these established 2D materials, sharing many similar electronic properties due to a hexagonal lattice, [10][11][12][13] the unique silicon-based 2D Kane-Mele topological insulator, 14 however, has a relatively large spin-orbit bandgap ( 1.55 eV ) which could be nearly doubled under an external strain.…”

Section: Introductionmentioning

confidence: 99%

Temperature- and frequency-dependent optical and transport conductivities in doped buckled honeycomb lattices

2018

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Thermal and dynamical properties of optical and transport conductivities in doped buckled honeycomb lattices are studied for various doping densities and bandgaps. At finite temperatures, a thermally-convoluted polarization function is calculated by employing analytically derived temperature-dependent chemical potentials. With this finite-temperature polarization function, the optical conductivity, originating from an induced polarization current, is obtained in the longwavelength limit, where both steps and negative peaks are shown as a function of frequency in its real and imaginary parts, respectively. Such spectral features can be used for analyzing plasmon dampings in silicene and ultrafast light modulations based on field-tunable bandgaps. Additionally, in the presence of static screening, derived with the aid of the polarization function, for impurity elastic scattering, the transport conductivities are calculated for different doping densities and bandgaps within the second-order Born approximation. The enhanced transport conductivity with a smaller bandgap at intermediate temperatures will lead to high-mobility electron transistors for ultrafast electronics.

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Section: Introductionmentioning

confidence: 99%

Temperature- and frequency-dependent optical and transport conductivities in doped buckled honeycomb lattices

2018

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“…In addition, a thorough experimental study for the density of states of germanene which had been synthesized on Ge/Pt crystals at finite temperatures was performed by using a scanningtunneling electron microscope. 50 The obtained virtually perfect linearly dependent density of states is clearly a proof of a 2D Dirac system. Furthermore, Friedel oscillations were not observed, implying the possible Klein paradox within the considered system.…”

Section: Introductionmentioning

confidence: 73%

Controlling plasmon modes and damping in buckled two-dimensional material open systems

Iurov

Gumbs

Huang

et al. 2017

Journal of Applied Physics

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Full ranges of both hybrid plasmon-mode dispersions and their damping are studied systematically by our recently developed mean-field theory in open systems involving a conducting substrate and a two-dimensional (2D) material with a buckled honeycomb lattice, such as silicene, germanene, and a group IV dichalcogenide as well. In this hybrid system, the single plasmon mode for a free-standing 2D layer is split into one acoustic-like and one optical-like mode, leading to a dramatic change in the damping of plasmon modes. In comparison with gapped graphene, critical features associated with plasmon modes and damping in silicene and molybdenum disulfide are found with various spin-orbit and lattice asymmetry energy bandgaps, doping types and levels, and coupling strengths between 2D materials and the conducting substrate. The obtained damping dependence on both spin and valley degrees of freedom is expected to facilitate measuring the open-system dielectric property and the spin-orbit coupling strength of individual 2D materials. The unique linear dispersion of the acoustic-like plasmon mode introduces additional damping from the intraband particle-hole modes which is absent for a free-standing 2D material layer, and the use of molybdenum disulfide with a large bandgap simultaneously suppresses the strong damping from the interband particle-hole modes.

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“…Experimentally observed linear Vshaped DOS was used to verify the Dirac-cone dispersion for germanene. 86 However, ρ d (E) becomes finite only above ∆ < , demonstrating the importance of a bandgap.…”

Section: Fig 1: (Color Online)mentioning

confidence: 99%

Thermal plasmons controlled by different thermal-convolution paths in tunable extrinsic Dirac structures

et al. 2017

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Analytic expressions for chemical potentials without any approximations are derived for all types of extrinsic (doped) gapped Dirac-cone materials including gapped graphene, silicene, germanene and single-layer transition metal dichalcogenides. In setting up our derivations, a reliable piecewiselinear model has been established for calculating the density-of-states in molybdenum disulfide, showing good agreement with previously obtained numerical results. For spin-and valley-resolved band structures, a decrease of chemical potential with increasing temperature is found as a result of enhanced thermal populations of an upper subband. Due to the broken symmetry with respect to electron and hole states in MoS2, the chemical potential is shown to cross a zero-energy point at sufficiently high temperatures. It is important to mention that the chemical potential at a fixed temperature can still be tuned by varying doping density and band structure of a system with an external electric or strain field. Since a thermal-convolution path (or a chemical-potential-dependent response function for the thermal convolution of fermions) starting from zero temperature must be selected in advance before obtaining finite-temperature properties of any collective quantities, e.g., polarizability, plasmon modes and damping, a control of their thermal dependence within a certain temperature range is expected for field-tunable extrinsic gapped Dirac-cone materials.

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Scanning tunneling spectroscopy study of the Dirac spectrum of germanene

Cited by 19 publications

References 28 publications

Temperature- and frequency-dependent optical and transport conductivities in doped buckled honeycomb lattices

Temperature- and frequency-dependent optical and transport conductivities in doped buckled honeycomb lattices

Controlling plasmon modes and damping in buckled two-dimensional material open systems

Thermal plasmons controlled by different thermal-convolution paths in tunable extrinsic Dirac structures

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