Anisotropic Quantum Confinement Effect and Electric Control of Surface States in Dirac Semimetal Nanostructures

Xiao, Xunwen; Yang, Shengyuan A.; Liu, Zhengfang; Li, Huili; Zhou, Guanghui

doi:10.1038/srep07898

Cited by 52 publications

(72 citation statements)

References 25 publications

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“…Na 3 Bi is a topological Dirac semimetal (TDS) with stable 3D Dirac points separated form the Γ point along the k z axis in its 1st Brillouin zone which has a linear band dispersion in all three momentum space directions [3,4]. The behavior of Dirac fermions in 3D opens up the possibility to study phenomena such as the chiral anomaly [5,6]; thin films geometry offers the opportunity to study ambipolar electronic devices [7], electron-hole pudding [8], along with the theoretical prediction of opening a band gap in excess of 300 meV in monolayer films [9] and a topological phase transition between trivial and non-trivial insulator that occurs at varying thickness or with applied electric field [10,11].…”

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confidence: 99%

Temperature-dependent n−p transition in a three-dimensional Dirac semimetal Na3Bi thin film

et al. 2017

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We study the temperature dependence (77 K -475 K) of the longitudinal resistivity and Hall coefficient of thin films (thickness 20 nm) of three dimensional topological Dirac semimetal Na 3 Bi grown via molecular beam epitaxy (MBE). The temperature-dependent Hall coefficient is electron-like at low temperature, but transitions to hole-like transport around 200 K. We develop a model of a Dirac band with electron-hole asymmetry in Fermi velocity and mobility (assumed proportional to the square of Fermi velocity) which explains well the magnitude and temperature dependence of the Hall resistivity. We find that the hole mobility is about 7 times larger than the electron mobility. In addition, we find that the electron mobility decreases significantly with increasing temperature, suggesting electron-phonon scattering strongly limits the room temperature mobility.

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confidence: 99%

Temperature-dependent n−p transition in a three-dimensional Dirac semimetal Na3Bi thin film

et al. 2017

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“…Interactive simulations have been included as supplemental data to enable more detailed exploration of these differences. The results obtained here are also straightforwardly generalized to any materials systems whose band structure is described by the same type of k p · Hamiltonian that forms the basis for our theoretical approach, including Dirac semimetals [39][40][41] and other surmised TIs such as Bi 2 Te 2 I 2 [42].…”

Section: Discussionmentioning

confidence: 72%

Manipulating topological-insulator properties using quantum confinement

Kotulla

Zülicke

2017

New J. Phys.

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Recent discoveries have spurred the theoretical prediction and experimental realization of novel materials that have topological properties arising from band inversion. Such topological insulators are insulating in the bulk but have conductive surface or edge states. Topological materials show various unusual physical properties and are surmised to enable the creation of exotic Majorana-fermion quasiparticles. How the signatures of topological behavior evolve when the system size is reduced is interesting from both a fundamental and an application-oriented point of view, as such understanding may form the basis for tailoring systems to be in specific topological phases. This work considers the specific case of quantum-well confinement defining two-dimensional layers. Based on the effective-Hamiltonian description of bulk topological insulators, and using a harmonic-oscillator potential as an example for a softer-than-hard-wall confinement, we have studied the interplay of band inversion and size quantization. Our model system provides a useful platform for systematic study of the transition between the normal and topological phases, including the development of band inversion and the formation of massless-Dirac-fermion surface states. The effects of bare size quantization, twodimensional-subband mixing, and electron-hole asymmetry are disentangled and their respective physical consequences elucidated.

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“…For a Na 3 Bi (or Cd 3 As 2 ) thin film confined in z-direction, 31, 32 the electron motion along z is quantized into discrete quantum well levels, forming quantum well subbands in the spectrum. 33,34 The resulting system generally becomes semiconducting. In the quantum well approximation, 35 each subband corresponds to a 2D slice in the original 36 so that the quasi-2D thin film becomes a QSH insulator if there is an odd number of inverted subbands, and is a trivial insulator if this number is even.…”

Section: Strain Tuning and Tpt In Bulk Materialsmentioning

confidence: 99%

Artificial gravity field, astrophysical analogues, and topological phase transitions in strained topological semimetals

Guan¹,

Yu²,

Liu³

et al. 2017

npj Quant Mater

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144

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Effective gravity and gauge fields are emergent properties intrinsic for low-energy quasiparticles in topological semimetals. Here, taking two Dirac semimetals as examples, we demonstrate that applied lattice strain can generate warped spacetime, with fascinating analogues in astrophysics. Particularly, we study the possibility of simulating black-hole/white-hole event horizons and gravitational lensing effect. Furthermore, we discover strain-induced topological phase transitions, both in the bulk materials and in their thin films. Especially in thin films, the transition between the quantum spin Hall and the trivial insulating phases can be achieved by a small strain, naturally leading to the proposition of a novel piezo-topological transistor device. Possible experimental realizations and analogue of Hawking radiation effect are discussed. Our result bridges multiple disciplines, revealing topological semimetals as a unique table-top platform for exploring interesting phenomena in astrophysics and general relativity; it also suggests realistic materials and methods to achieve controlled topological phase transitions with great potential for device applications.npj Quantum Materials (2017) 2:23 ; doi:10.1038/s41535-017-0026-7 INTRODUCTIONRelativity is a fundamental aspect for all elementary particles in the high-energy regime. In condensed matter physics, however, the relevant energy scale we probe is much lower (compared with, e.g., the electron rest mass), hence the electronic dynamics is usually considered as non-relativistic. Nonetheless, due to interactions with lattice and between electrons themselves, the electron properties in crystalline solids are strongly renormalized, and the resulting low-energy electron quasiparticles can behave drastically different from free electrons. Remarkably, in a class of recently discovered topological semimetal materials, the band structures feature nontrivial band-crossings close to the Fermi level, around which the low-energy quasiparticles become massless and resemble relativistic particles. For example, in socalled Weyl semimetals, the Fermi surface consists of isolated band-crossing points, each carrying a topological charge of ±1 corresponding to its chirality, and the low-energy quasiparticles mimic the Weyl fermions in high-energy physics.1, 2 With further protection from crystalline symmetry, a pair of Weyl points can be stabilized at the same point (called the Dirac point) in the energy-momentum space, realizing the Dirac semimetal (DSM) phase.3 A number of 3D materials have been predicted to host Weyl/Dirac points.4-9 Some of them, including the DSMs Na 3 Bi and Cd 3 As 2 , 10,11 have been confirmed in recent experiments.

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Anisotropic Quantum Confinement Effect and Electric Control of Surface States in Dirac Semimetal Nanostructures

Cited by 52 publications

References 25 publications

Temperature-dependent n−p transition in a three-dimensional Dirac semimetal Na3Bi thin film

Temperature-dependent n−p transition in a three-dimensional Dirac semimetal Na3Bi thin film

Manipulating topological-insulator properties using quantum confinement

Artificial gravity field, astrophysical analogues, and topological phase transitions in strained topological semimetals

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