Low-energy electronic properties of a Weyl semimetal quantum dot

Abstract

It is necessary to study the properties of Weyl semimetal nanostructures for potential applications in nanoelectronics. Here we study the Weyl semimetal quantum dot with a most simple model Hamiltonian with only two Weyl points. We focus on the low-energy electronic structure and show the correspondence to that of three-dimensional Weyl semimetal, such as Weyl point and Fermi arc. We find that there exist both surface and bulk states near Fermi level. The direct gap of bulk states reaches the minimum with the location determined by Weyl point. There exists a quantum number with only several values supporting surface states, which is the projection of Fermi arc. The property of surface state is studied in detail, including circular persistent current, orbital magnetic moment, and chiral spin polarization. Surface states will be broken by a strong magnetic field and evolve into Landau levels gradually. Simple expressions are derived to describe the energy spectra and electronic properties of surface states both in the presence and absence of magnetic field. In addition, this study may help design a method to verify Weyl semimetal by separating out the signal of surface states since quantum dot has the largest surface-to-volume ratio.

Localized spin-orbit polaron in magnetic Weyl semimetal Co3Sn2S2

“…Thus, our experimental findings are consistent with the picture that the spin-polarized localized states generate persistent circulating diamagnetic currents and large orbital magnetization around the S-vacancy, which acts as a magnetic (anti-)dot extending to the neighboring S atoms. Most recently, such circulating persistent currents induced by the topological surface states with diamagnetic moment around quantum dots in Weyl semimetals were theoretically predicted27 , which provides further and more direct support for our experimental findings and theoretical interpretation of the S-vacancy as a quantum dot.…”

“…The anomalous Zeeman shift observed here, however, comes from a localized bound state and corresponds to the overall magnetic field response of a net physical magnetic moment. The large orbital magnetization of the SOP most likely originates from the persistent circulating current around the S-vacancy due to the Berry phase and magnetoelectric effect of the topological Weyl semimetal27 .The possible origin of the orbital magnetization of the SOP is new and intriguing. In dilute magnetic semiconductors (DMS)28,29 such as (Ga, Mn)As, the doped magnetic ion Mn 2+ induces a magnetic polaron through the exchange coupling to the weakly correlated itinerant p-orbital electrons in the hole-band with spin-orbit coupling.…”

Research progress on topological nodal line semimetals

“…在拓扑绝缘体的表面或边缘拥 有稳定的零能隙金属态, 利用这些非平庸的表面态或 者边缘态有望实现低能耗量子输运和拓扑量子计 算 [10] . 在拓扑半金属领域, 科学家根据能带的交叉方 式和色散关系也定义了不同种类的拓扑半金属, 包括 外尔半金属 [12,13] 、狄拉克半金属 [14,15] 、节线半金 域具有广泛的应用前景 [12,[18][19][20][21][22] . 在拓扑材料中对称性一直扮演着至关重要的角 色.…”

Magnetic Weyl semimetal finally confirmed

“…The pursuit of both nonmagnetic and magnetic WSMs has succeeded considerably. This has stimulated extensive theoretical and experimental efforts to explore intriguing physical properties and effects associated with Weyl nodes, including anomalous Hall effect, anomalous Nernst effect, chiral anomaly effect, zero sound [11], nonlinear optical effect [12], three-dimensional quantum Hall effect [13], unique charge and spin current [14], and catalysis [15]. High pressure [16,17] and other ways to introduce coupling with magnetism, superconductivity, ferroelectricity, phonon, photon, and magnon will bring us more phenomena in WSMs.…”