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Antimonene is a promising two-dimensional (2D) material that is calculated to have a significant fundamental bandgap usable for advanced applications such as field-effect transistors, photoelectric devices, and the quantum-spin Hall (QSH) state. Herein, we demonstrate a phenomenon termed topological proximity effect, which occurs between a 2D material and a three-dimensional (3D) topological insulator (TI). We provide strong evidence derived from hydrogen etching on Sb2Te3 that large-area and well-ordered antimonene presents a 2D topological state. Delicate analysis with a scanning tunneling microscope of the evolutionary intermediates reveals that hydrogen etching on Sb2Te3 resulted in the formation of a large area of antimonene with a buckled structure. A topological state formed in the antimonene/Sb2Te3 heterostructure was confirmed with angle-resolved photoemission spectra and density-functional theory calculations; in particular, the Dirac point was located almost at the Fermi level. The results reveal that Dirac fermions are indeed realized at the interface of a 2D normal insulator (NI) and a 3D TI as a result of strong hybridization between antimonene and Sb2Te3. Our work demonstrates that the position of the Dirac point and the shape of the Dirac surface state can be tuned by varying the energy position of the NI valence band, which modifies the direction of the spin texture of Sb-BL/Sb2Te3via varying the Fermi level. This topological phase in 2D-material engineering has generated a paradigm in that the topological proximity effect at the NI/TI interface has been realized, which demonstrates a way to create QSH systems in 2D-material TI heterostructures.

We study the quantum oscillations in the BiSbTe3 topological insulator. In addition to the Shubnikov-de Haas (SdH) oscillation, the Aharonov-Bohm-like (ABL) oscillations are also observed. The ABL oscillation period is constant at each Landau level (LL) which is determined from the SdH oscillation. The shorter ABL oscillation periods are observed at lower LLs. The oscillation period is proportional to the square root of the LL at temperatures. The ratio of the ABL oscillation period to the effective mass is weak LL dependence. The LL-dependent ABL oscillation might originate from the LL-dependent effective mass.

The conductivity increases as thickness decreases in a series of Sb2SeTe2 topological insulator nanosheets with thickness ranging from 80 to 200 nm, where the sheet conductance is proportional to the thickness. The corresponding sheet conductance of the surface state is 8.7 e2/h which is consistent with the values extracted from the temperature dependent Shubnikov-de Haas oscillations at high magnetic fields. The extracted Fermi momentum is the same as the results from the ARPES value, and the Berry phase is π. These support that the thickness dependent sheet conductance originates from the combination of the surface state and the bulk state.

A photocurrent was applied to a Sb2SeTe2 topological insulator nanosheet at a wavelength of 325 nm, and it exhibited extremely high performance such that the responsivity and photoconductive gain are 354 A W−1 and 1531, respectively, at a bias of 0.1 V. This photoresponse is orders of magnitude higher than most reported values for topological insulators and two-dimensional transitional metal dichalcogenides. The photoresponse is linear with the applied voltage. Responsivity and gain under vacuum are higher than that in air by a factor of 2.5. This finding suggests that the Sb2SeTe2 topological insulator nanosheet has great potential for ultraviolet optoelectronic device applications.

The photocurrent was performed in the Sb2SeTe2 topological insulator at a wavelength of 532 nm. It exhibits extremely high performance that the responsivity and the photoconductive gain reach 2293 AW−1 and 5344 at 1 V. This high photoresponse is orders of magnitude higher than most reported values in topological insulators and two-dimensional transitional metal dichalcogenides. This finding suggests that the Sb2SeTe2 nanoflake has great potential for future optoelectronic device applications.

A topological insulator (TI) is a quantum material in a new class with attractive properties for physical and technological applications. Here we derive the electronic structure of highly crystalline Sb2Te2Se single crystals studied with angle-resolved photoemission spectra. The result of band mapping reveals that the Sb2Te2Se compound behaves as a p-type semiconductor and has an isolated Dirac cone of a topological surface state, which is highly favored for spintronic and thermoelectric devices because of the dissipation-less surface state and the decreased scattering from bulk bands. More importantly, the topological surface state and doping level in Sb2Te2Se are difficult to alter for a cleaved surface exposed to air; the robustness of the topological surface state defined in our data indicates that this Sb2Te2Se compound has a great potential for future atmospheric applications.

We report the Aharonov-Bohm (AB) oscillation in the BiSbTe3 topological insulator macroflake. The magnetoresistance reveals periodic oscillations. The oscillation index number reveals the Berry phase is π which supports the oscillation originates from the surface state. The AB oscillation frequency increases as temperature decreases, and the corresponding phase coherence length is consistent with that extracted from the weak antilocalization. The phase coherence length is proportional to T−1∕2. The magnetoresistance ratio reaches 700% (1000%) at 9 T (14 T) and 2 K, and it is proportional to the carrier mobility. The magnetoresistance ratio is larger than all reported values in (Bi, Sb)2(Te, Se)3 topological insulators.

The robustness of Sb2SeTe2 topological insulators against surface oxidation has been comparatively investigated through their magneto-transport and X-ray photoelectron spectroscopic properties with samples freshly cleaved or exposed to air over various timeframes. The magnetoresistance data exhibit Shubnikov-de Haas oscillations with the same period of oscillations for all samples regardless of surface oxidation, whereas the core-level electron binding energies of the constituent elements vary. That there is no shift in Fermi levels and no smearing-out in the amplitude of oscillations suggests that the surface states of the studied topological insulators are impervious to surface oxidation.

Large magnetoresistance (MR) has been widely reported in the A2B3 (A = Sb or Bi; B = Se or Te) family of topological insulators (TIs). Sb2Se3 is not a TI that was confirmed by the extracted zero Berry phase and the X-ray diffraction. An extremely large MR was observed in the Sb2Se3 crystals. This large MR increased quadratically with the magnetic field applied. The observed MR ratio was 830% at 10 K and 9 T, which was larger than that previously reported for all A2B3 family TIs. This large MR originated from two carriers with high mobility. The inversely square root of the MR ratio was proportional to the resistance.

A non-saturating linear magnetoresistance (MR) is observed in Sb2SeTe2 topological insulator. The results show that the MR slope and the critical magnetic field of the linear MR are proportional to the carrier mobility and inverse mobility, respectively. These are consistent with the prediction of a model, which is constructed by Parish and Littlewood [Nature 426, 162 (2003)], in the weak mobility fluctuation condition. The Kohler plot of the magnetoresistance does not collapse onto a single curve that supports the multi-carriers scattering mechanisms.

A topological insulating Bi2Te3 single crystal was successfully grown with good uniformity using a home-made resistance-heated floated zone furnace. The temperature-dependent resistance and Hall voltage confirm that the transport is metallic and the overall carriersareholes. The angle and temperature dependence of the quantum Shubnikov–de Haas oscillation period amplitude suggests that the transport comes from the carriers of surface states. The Berry phase, determined from Landau level diagram, also reveals that the transport carriers are Dirac fermions. In contrast with many previous publications, the transport parameters relating to the surface carriers derived from the relationship of the Lifshitz–Kosevich (LK) theory are consistent with angle resolved photoemission spectroscopy results.