Evidence of surface transport and weak antilocalization in a single crystal of theBi2Te2Setopological insulator

Abstract

Topological insulators are known to their metallic surface states, a result of strong-spin-orbital coupling, that show unique surface transport phenomenon. But these surface transports are buried in presence of metallic bulk conduction. We synthesized very high quality Bi2Te2Se single crystals by modified Bridgman method, that possess high bulk resistivity of >20 Ωcm below 20 K, whereas the bulk is mostly inactive and surface transport dominates. Temperature dependence resistivity follows the activation law like a gap semiconductor in temperature range 20-300 K. We designed a special measurement geometry, which aims to extract the surface transport from the bulk. This special geometry is applied to measure the resistance and found that Bi2Te2Se single crystal exhibits a cross over from bulk to surface conduction at 20 K. Simultaneously, the material also shows strong evidence of weak anti-localization in magneto-transport due to the protection against scattering by conducting surface states. This novel simple geometry is an easy route to find the evidence of surface transport in topological insulators, which are the promising materials for future spintronic applications.Topological insulators (TIs) have recently attracted significant attention since they are materialized into a new state of quantum matters, and they possess topologically protected metallic states on their edges or surfaces.1,2 These conducting SSs originate from the inversion of bulk bands due to the results of strong-spin-orbital coupling. Therefore, these novel metallic states are a subject of intensive investigations because of not only its fundamental novelty but also its high potential applications for spintronics devices 3 and quantum computations. 4In 3D TIs, the topological surface states have been successfully investigated by surface-sensitive techniques as angle-resolved photoemission spectroscopy 5,6 and scanning tunneling microscopy 7,8 . However, the evidences of transport through the surface sates remain a challenge due to the presence of the parallel bulk conducting channels that usually dominate the transport properties. 9-11Various strategies to improve surface conductivity, e.g., studying thin films or nano-flacks 6,12-16 , gating 15,17,18 , and doping 10,11,19 have been employed. Among the all known TIs, the ternary tetradymite Bi 2 Te 2 Se (BTS) has largely been investigated material that gives excellent performance of surface in temperature dependence resistivity 6,[12][13][14][15][16]20 . It shows large bulk resistivity due to the nearly perfect crystalline structure, and it has been predicted nearly perfect Dirac cones in terms of less entanglement of bulk and surface states 6,16,19,20 . The quantum oscillations have also been observed in BTS 20-22 and doped BTS 10,19 bulk samples, and they show surfaceddominated transport contributes up to 70% of the total conductance 10,20 . Besides showing this metallic behavior, excellent performance of the surface states of TIs appears in magneto-conductance in effect of weak antiloca...

Charge puddles in a completely compensated topological insulator

“…compositional gradient [1] or lightly doped Bi 1.9 Tl 0.1 Te 3 samples (28 mΩcm) [17]. However, they are lower than those obtained for heavy chemical doping in the Bi 2 -Te x 3 Se x system (1-20 Ωcm for = x 0.9 1 -) [5,10,12]. It should be noted that although Bi 2 Te 2 Se has the same crystal structure as Bi 2 Te 3 and is commonly referred to as chemically doped Bi 2 Te 3 , the electronic structures of the two compounds are in fact quite different, particularly near the band edges.…”

Topological delocalization and tuning of surface channel separation in Bi2Se2Te Topological Insulator Thin films

“…The transport signature of the surface Dirac states have been achieved unambiguously with very less parasitic bulk effects in such ternary and quaternary TI flakes/single crystals 21, 22 . Most of the transport studies on high quality BTS and BSTS has remained confined to single crystals or thin flakes exfoliated from these single crystals 4, 5, 14, 18, 21, 23–25 .…”

Scientific and Technological Assessment of Iron Pyrite for Use in Solar Devices

“…Herein, an attempt is made to directly measure the difference between the bulk and surface conductiont hrough a temperature-dependenti nvestigation of the electrical resistance for some specific geometrical configurations similar to those used by Shekhar et al [65] and Wolgast and co-workers [66,67] An atural cube-shapedc rystal (from Navajun, Spain) with as ide length of approximately 1cmw as cut along the (100) plane using ad iamond saw into square wafers of 1mm thickness.T he wafers were polished to removea ny surface artefacts caused by the cutting. All characterizations were performed on polished pyrite wafers,a ss hown in Figure 8.…”