Quantum transport and shot noise in two-dimensional semi-Dirac system

Abstract

Two-dimensional (2D) semi-Dirac systems, such as 2D black phosphorus and arsenene, can exhibit a rich topological phase transition between insulating, semi-Dirac, and band inversion phases when subjected to an external modulation. How these phase transitions manifest within the quantum transport and shot noise signatures remains an open question thus far. Here, we show that the Fano factor converges to the universal [Formula: see text] at the semi-Dirac phase and transits between the sub-Poissonian ([Formula: see text]) and the Poissonian shot noise ([Formula: see text]) limit at the band inversion and the insulating phase, respectively. Furthermore, the conductance of a 2D semi-Dirac system converges to the contrasting limit of [Formula: see text] and [Formula: see text] at the band inversion and the insulating phases, respectively. The quantum tunneling spectra exhibits a peculiar coexistence of massless and massive Dirac quasiparticles in the band inversion regime, thus providing a versatile sandbox to study the tunneling behavior of various Dirac quasiparticles. These findings reveal the rich interplay between band topology and quantum transport signatures, which may serve as smoking gun signatures for the experimental studies of semi-Dirac systems near the topological phase transition.

Designing edge states from fractional polarization insulators

“…Due to the existence of delocalized states around the k x = 0 momenta, the finite size effect, which can destroy the quantum spin and anomalous hall effect [45,46], can be exploited to produce disconnected edge states analogous to helical-like and chiral-like edge states, not possible through the chiral symmetry-breaking terms. The tunability of these disconnected edge states can provide new avenues in designing topological domain walls in electronic devices [30,50,51] and heterojunctions [52,53], and also yield unusual behaviors in physical mechanisms such as in electron emission [54][55][56][57] and transport [26,30].…”

“…Unlike the usual isotropic model in the well-celebrated graphene [22] and other metamaterials [23], the anisotropic model has a modified nearest neighbor (NN) hopping term and is a tunable parameter [24,25]. This tunability merges two Dirac cones in the band structure and results in the topological phase transition (see figure 1(b)) from band-inversion, semi-Dirac, and insulating phase characterized by different transport signatures [26][27][28][29] and of potential in designing valleytronics device [30][31][32]. Apart from photonic [33], polariton materials [34] and α-dice lattice [35][36][37], the anisotropic honeycomb lattices are also expected in anisotropic graphene [38] and phosphorene [19,39], monolayer arsenene [40] and silicene oxide [41].…”

Quantifying the photocurrent fluctuation in quantum materials by shot noise

“…For example, it has been well-established that the shot noise (SN) can probe the quantum statistics of the quasi-particles and measure their effective charge in mesoscopic systems 39 – 43 . In addition, the SN has been used to reveal the topological phase transition of 2D semi-Dirac materials 44 and to probe the nonlocal hot-electron energy dissipation 45 .…”