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Quantum transport measurements including the Altshuler-Aronov-Spivak (AAS) and Aharonov-Bohm (AB) effects, universal conductance fluctuations (UCF), and weak anti-localization (WAL) have been carried out on epitaxial Bi thin films ($10-70$…

Mesoscale and Nanoscale Physics · Physics 2017-07-07 Kai Zhu , Lin Wu , Xinxin Gong , Shunhao Xiao , Shiyan Li , Xiaofeng Jin , Mengyu Yao , Dong Qian , Meng Wu , Ji Feng , Qian Niu , Fernando de Juan , Dung-Hai Lee

In integrating topological insulators (TIs) with conventional materials, one crucial issue is how the topological surface states (TSS) will behave in such heterostructures. We use first-principles approaches to establish accurate tunability…

Materials Science · Physics 2013-01-23 Guangfen Wu , Hua Chen , Yan Sun , Xiaoguang Li , Ping Cui , Cesare Franchini , Jinlan Wang , Xing-Qiu Chen , Zhenyu Zhang

Topological insulators have been predicted to exhibit a variety of interesting phenomena including a quantized magnetoelectric response and novel spintronics effects due to spin textures on their surfaces. However, experimental observation…

Topological insulators (TI) are a phase of matter that host unusual metallic states on their surfaces. Unlike the states that exist on the surface of conventional materials, these so-called topological surfaces states (TSS) are protected…

We report transport measurements on Josephson junctions consisting of Bi2Te3 topological insulator (TI) thin films contacted by superconducting Nb electrodes. For a device with junction length L = 134 nm, the critical supercurrent Ic can be…

Optical band gap properties of high-quality few-layer topological insulator Bi2Se3 thin films grown with magnetron sputtering are investigated using broadband absorption spectroscopy. We provide direct optical evidence of a rigid blue-shift…

Materials Science · Physics 2017-05-24 Yub Raj Sapkota , Asma Alkabsh , Aaron Walber , Hassana Samassekou , Dipanjan Mazumdar

Three-dimensional (3D) topological insulators (TI) are novel quantum materials with insulating bulk and topologically protected metallic surfaces with Dirac-like band structure. The spin-helical Dirac surface states are expected to host…

Material defects remain as the main bottleneck to the progress of topological insulators (TIs). In particular, efforts to achieve thin TI samples with dominant surface transport have always led to increased defects and degraded mobilities,…

Transient reflectivity traces measured for nanometer-sized films of the topological insulator Bi2Se3 revealed GHz-range oscillations driven within the relaxation of hot carriers photoexcited with ultrashort laser pulses of 1.51 eV photon…

Mesoscale and Nanoscale Physics · Physics 2015-05-20 Yuri D. Glinka , Sercan Babakiray , Trent A. Johnson , Mikel B. Holcomb , David Lederman

Spatial confinement of electronic topological surface states (TSS) in topological insulators poses a formidable challenge because TSS are protected by time-reversal symmetry. In previous works formation of a gap in the electronic spectrum…

Topological insulators are guaranteed to support metallic surface states on an insulating bulk, and one should thus expect that the electronic transport in these materials is dominated by the surfaces states. Alas, due to the high remaining…

In chalcogenide topological insulator materials, two types of magneto-resistance (MR) effects are widely discussed: a positive MR dip around zero magnetic field associated with the weak antilocalization (WAL) effect and a linear MR effect…

Mesoscale and Nanoscale Physics · Physics 2015-12-31 Z. H. Wang , L. Yang , X. T. Zhao , Z. D. Zhang , Xuan P. A. Gao

In this Rapid Communication we investigate the coupling between excited electrons and phonons in the highly anisotropic electronic structure of the prototypical topological insulator Bi$_2$Te$_3$. Using time- and angle-resolved…

Mesoscale and Nanoscale Physics · Physics 2016-10-13 E. Golias , J. Sánchez-Barriga

Infrared transparent conductors have long been sought due to their broad optoelectronic applications in the infrared wavelength range. However, the search for ideal materials has been limited by the inherent trade-off between electrical…

We report the composition and gate voltage induced tuning of transport properties in chemically synthesized Bi2(Te1-xSex)3 nanoribbons. It is found that increasing Se concentration effectively suppresses the bulk carrier transport and…

Mesoscale and Nanoscale Physics · Physics 2013-05-21 ZhenHua Wang , Richard L. J. Qiu , Chee Huei Lee , ZhiDong Zhang , Xuan P. A. Gao

Mechanical exfoliation of bulk crystals has been widely used to obtain thin topological insulator (TI) flakes for device fabrication. However, such a process produces only micro-sized flakes that are highly irregular in shape and thickness.…

In this study, we address the phase coherent transport in a sub-micrometer-sized Hall bar made of epitaxial Bi2Se3 thin film by probing the weak antilocalization (WAL) and the magnetoresistance fluctuation below 22 K. The WAL effect is well…

Compensation of intrinsic charges is widely used to reduce the bulk conductivity of 3D topological insulators (TIs). Here we use low temperature electron irradiation-induced defects paired with in-situ electrical transport measurements to…

Materials Science · Physics 2016-09-27 C. W. Rischau , A. Ubaldini , E. Giannini , C. J. van der Beek

We present a study of the structural and electronic properties of highly doped topological insulator Bi2Se3 single crystals synthesized by the Bridgman method. Lattice structural characterizations by X-ray diffraction, scanning tunneling…

Materials Science · Physics 2012-12-07 Helin Cao , Suyang Xu , Ireneusz Miotkowski , Jifa Tian , Deepak Pandey , M. Zahid Hasan , Yong P. Chen

MXenes stand out from other 2D materials because they combine very good electrical conductivity with hydrophilicity, allowing cost-effective processing as thin films. Therefore, there is a high fundamental interest in unraveling the…