Gate-Tunable Surface States in Topological Insulator β-Ag₂Te with High Mobility

Abstract

Stimulated by novel properties in topological insulators, experimentally realizing quantum phases of matter and employing control over their properties have become a central goal in condensed matter physics. β-silver telluride (Ag 2 Te) is predicted to be a new type narrow-gap topological insulator. While enormous efforts have been plunged into the topological nature in silver chalcogenides, sophisticated research on low-dimensional nanostructures remains unexplored. Here, we report the record-high bulk carrier mobility of 298 600 cm 2 /(V s) in high-quality Ag 2 Te nanoplates and the coexistence of the surface and bulk state from systematic Shubnikov−de Haas oscillations measurements. By tuning the correlation between the top and bottom surfaces, we can effectively enhance the contribution of the surface to the total conductance up to 87% at 130 V. These results are instrumental to the highmobility physics study and even suitable to explore exotic topological phenomena in this material system.

Extended Short-Wavelength Infrared Photoluminescence and Photocurrent of Nonstoichiometric Silver Telluride Colloidal Nanocrystals

“…Silver chalcogenide has attracted great interest in various applications such as memory due to its outstanding electrical properties, low thermal conductivity, and crystal structures sensitive to environmental conditions. − These peculiar features are interestingly reflected in the nanocrystals. For instance, depending on the temperature and pressure, silver telluride nanocrystals (Ag 2 Te NCs) change their crystal structure, eventually leading to a phase transition from a semiconductor to a superionic conductor.…”

From Low-Field Sondheimer Oscillations to High-Field Very Large and Linear Magnetoresistance in a SrTiO3-Based Two-Dimensional Electron Gas

“…A few studies also mention a linear magnetoresistance (MR) for perpendicular magnetic field B , with, in some cases, a very large amplitude (>500% at 9 T) . This is reminiscent of a giant, nonsaturating linear MR reported in various systems including narrow band gap semiconductors, graphene, , semimetals, − and topological insulators. , Two main scenarios have been proposed to explain this behavior. Abrikosov , established that impurity scattering of Dirac fermions confined to the lowest Landau level, modeling quasi-gapless semiconductors, results in a positive quantum MR varying linearly with B .…”

“…13 This is reminiscent of a giant, nonsaturating linear MR reported in various systems including narrow band gap semiconductors, 15 graphene, 16,17 semimetals, 18−20 and topological insulators. 21,22 Two main scenarios have been proposed to explain this behavior. Abrikosov 23,24 established that impurity scattering of Dirac fermions confined to the lowest Landau level, modeling quasigapless semiconductors, results in a positive quantum MR varying linearly with B. Alternatively, Parish and Littlewood 25,26 introduced a classical model describing the behavior of charges moving through an array of four-terminal random resistors where they are subjected to a driving current along one direction and a magnetic field perpendicular to the array.…”

Enhanced Thermoelectric Performance of Nanostructured Nickel-Doped Ag2Te

“…Silver telluride (Ag 2 Te) is an interesting and attractive nonmagnetic topological insulator at ambient conditions , with many intriguing properties such as the structural phase transition from the low-temperature monoclinic phase β-Ag 2 Te to high-temperature face-centered cubic (fcc) phase α-Ag 2 Te near 417 K, , pressure-induced charge density wave (CDW) phase, and structural , and electronic topological phase transitions. While α-Ag 2 Te phase is a superionic conductor, its β-phase is a narrow-band gap (∼0.05 eV) semiconductor with high carrier mobility and low κ l due to the Ag-atoms-induced disordered structure in the Ag 2 Te lattice, making it a suitable TE material. ,, Although its low effective mass (∼10 –2 of free electron mass) favors the small S , high mobility makes both σ and κ e large.…”