Elemental Topological Dirac Semimetal α‐Sn with High Quantum Mobility

Abstract

Abstractα‐Sn provides an ideal avenue to investigate novel topological properties owing to its rich diagram of topological phases and simple elemental material structure. Thus far, however, the realization of high‐quality α‐Sn remains a challenge, which limits the understanding of its quantum transport properties and device applications. Here, epitaxial growth of α‐Sn on InSb (001) with the highest quality thus far is presented. The studied samples exhibit unprecedentedly high quantum mobilities of both the surface state (30 000 cm2 V−1 s−1), which is ten times higher than the previously reported values, and the bulk heavy‐hole state (1800 cm2 V−1 s−1), which is never obtained experimentally. These excellent features allow quantitative characterization of the nontrivial interfacial and bulk band structure of α‐Sn via a thorough investigation of Shubnikov–de Haas oscillations combined with first‐principles calculations. The results firmly identify that α‐Sn grown on InSb (001) is a topological Dirac semimetal (TDS). Furthermore, a crossover from the TDS to a 2D topological insulator and a subsequent phase transition to a trivial insulator when varying the thickness of α‐Sn are demonstrated. This work indicates that α‐Sn is an excellent model system to study novel topological phases and a prominent material candidate for topological devices.

Optical absorption and shape transition in neutral SnNclusters withN≤ 40: a photodissociation spectroscopy and electric beam deflection study

“…1 It is in particular this nonmetal-to-semiconductor-to-metal transition along the group of these tetrel elements (referring to the most common valency of four) that intrigues engineers and researchers alike. With tin being on the very edge of this transition, it exhibits, as a consequence, two stable allotropes, the gray diamond cubic α-Sn and the white body-centered tetragonal β-Sn, resembling the zero-gap semiconductor 2 (<286 K) and metal nature of this material, respectively. Albeit standing in the shadows of silicon (and also germanium) dominating the semiconductor industry, tin offers various desirable properties such as being non-toxic, inexpensive and a widespread element.…”

Large magnetoelectric resistance in the topological Dirac semimetal α-Sn

“…In the presence of a tensile strain along the [001] or [111] direction, however, the two bands cross each other near the Fermi level. This band crossing forms two Dirac points and gives rise to a TDS phase ( 22 , 27 – 29 ). One of these Dirac points is shown in Fig.…”

“…This mismatch yields a perpendicular tensile strain in the α-Sn films. This strain pushes the films into a TDS phase ( 22 , 27 – 29 ). The (111) orientation leads to the hexagonal warping depicted in Fig.…”

Photon Drag Currents and Terahertz Generation in α-Sn/Ge Quantum Wells

“…For example, α-Sn films were successfully grown on an InSb(111) substrate [ 16 ]. Further research demonstrated that extremely high quality α-Sn films with record hard mobilities of 30,000 cm 2 V −1 s −1 could be obtained on InSb(001) substrates [ 17 ]. α-Sn films are extremely sensitive to strain and can be tuned to transition from a topological Dirac semimetal (TDS) to a two-dimensional topological insulator (2DTI) by varying their thickness [ 16 , 17 ].…”

“…Further research demonstrated that extremely high quality α-Sn films with record hard mobilities of 30,000 cm 2 V −1 s −1 could be obtained on InSb(001) substrates [ 17 ]. α-Sn films are extremely sensitive to strain and can be tuned to transition from a topological Dirac semimetal (TDS) to a two-dimensional topological insulator (2DTI) by varying their thickness [ 16 , 17 ]. It was also discovered that a system of a-Sn/CdTe quantum well (QW) undergoes a phase transformation when the well width increases above a critical value of 8 nm [ 18 ].…”