Electrical transport and optical studies of spin orbit coupled topological phases in different correlation regimes

Abstract

The interplay of spin-orbit coupling (SOC) and electron-electron correlation in different regimes gave birth to many novel topological phases with exotic properties ranging from quantum transport to superconductivity. One of those phases, topological insulators(TI), attract attention widely due to its promising potential in building next-generation quantum computers. Strong TI (for example, Bi2Se3, BiSbTeSe, etc.), the most popular subclass of TI, has been investigated extensively. Recently, another subclass of TI known as a dual topological insulator(DTI) is being realized as new material. One of the examples of DTI is Bi1Te1, recently discovered as a topological system to host a weak TI state on the sides and topological crystalline insulating (TCI) state on the remaining surfaces. On the contrary, quantum spin liquid (QSL), another new topological phase, emerges due to strong electron-electron correlation. Honeycomb material RuCl3 has been studied as a quantum spin liquid candidate combining the Kitaev model and Jackeli-Khaliullin theory. In the 1st work, we synthesized the single crystals of pure Bi1Te1 and Sb-doped Bi1Te1 (Bi0.88Sb0.05Te1) via the modified Bridgmann method. After characterizing the single crystal by XRD, Raman spectroscopy, XPS, and EPMA, we investigated the electrical transport properties of the devices fabricated out of nanoflakes exfoliated from the as-grown crystals in the presence of out-of-plane and in-plane magnetic fields. We observed weak anti-localization (WAL), an important feature in low-field magneto-conductance to quantify the coherently conducting surface states. We analyzed WAL using Hikami-Larkin-Nagaoka equation. The phase coherence length (Land#981;) vs. T indicates the dephasing mechanism via 2D electron-phonon interaction in both cases: pure Bi1Te1 and Sb-doped Bi1Te1. With increasing thickness of the nanodevice, the dominance of the electron-phonon interaction increases. Hall effect further confirms the negative sign of the majority charge carriers and yields carrier densit...