Spin accumulation in topological insulator thin films—influence of bulk and topological surface states

AbstractPd$$_{3}$$ 3 Bi$$_{2}$$ 2 S$$_{2}$$ 2 (PBS) is a recently proposed topological semimetal candidate. However, evidence for topological surface states have not yet been revealed in transport measurements due to the large mobility of bulk carriers. We report the growth and magneto-transport studies of PBS thin films where the mobility of the bulk carriers is reduced by two orders of magnitude, revealing for the first time, contributions from the 2-dimensional (2D) topological surface states in the observation of the 2D weak anti-localization (WAL) effect in magnetic field and angle dependent conductivity measurements. The magnetotransport data is analysed within the 2D Hikami-Larkin-Nagaoka (HLN) theory. The analysis suggests that multiple conduction channels contribute to the transport. It is also found that the temperature dependence of the dephasing length can’t be explained only by electron-electron scattering and that electron-phonon scattering also contributes to the phase relaxation mechanism in PBS films.

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Strain driven emergence of topological non-triviality in YPdBi thin films

Scientific Reports ◽

10.1038/s41598-021-86936-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Vishal Bhardwaj ◽

Anupam Bhattacharya ◽

Shivangi Srivastava ◽

Vladimir V. Khovaylo ◽

Jhuma Sannigrahi ◽

...

Keyword(s):

Thin Films ◽

Heavy Fermion ◽

Critical Role ◽

Surface States ◽

Strain Engineering ◽

Emergent Properties ◽

Spintronic Devices ◽

Topological States ◽

Topological Surface ◽

Strained Films

AbstractHalf-Heusler compounds exhibit a remarkable variety of emergent properties such as heavy-fermion behaviour, unconventional superconductivity and magnetism. Several of these compounds have been predicted to host topologically non-trivial electronic structures. Remarkably, recent theoretical studies have indicated the possibility to induce non-trivial topological surface states in an otherwise trivial half-Heusler system by strain engineering. Here, using magneto-transport measurements and first principles DFT-based simulations, we demonstrate topological surface states on strained [110] oriented thin films of YPdBi grown on (100) MgO. These topological surface states arise in an otherwise trivial semi-metal purely driven by strain. Furthermore, we observe the onset of superconductivity in these strained films highlighting the possibility of engineering a topological superconducting state. Our results demonstrate the critical role played by strain in engineering novel topological states in thin film systems for developing next-generation spintronic devices.

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Spectroscopic signature of surface states and bunching of bulk subbands in topological insulator ( Bi0.4Sb0.6)2Te3 thin films

Physical Review B ◽

10.1103/physrevb.105.035122 ◽

2022 ◽

Vol 105 (3) ◽

Author(s):

Liesbeth Mulder ◽

Carolien Castenmiller ◽

Femke J. Witmans ◽

Steef Smit ◽

Mark S. Golden ◽

...

Keyword(s):

Thin Films ◽

Topological Insulator ◽

Surface States

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Studies on the origin of the interfacial superconductivity of Sb2Te3/Fe1+yTe heterostructures

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1914534117 ◽

2019 ◽

Vol 117 (1) ◽

pp. 221-227 ◽

Cited By ~ 1

Author(s):

Jing Liang ◽

Yu Jun Zhang ◽

Xiong Yao ◽

Hui Li ◽

Zi-Xiang Li ◽

...

Keyword(s):

Layer Thickness ◽

Topological Insulator ◽

Surface States ◽

The Other ◽

Majorana Fermions ◽

Bulk Conductivity ◽

Indirect Coupling ◽

Topological Surface ◽

Excess Fe

The recent discovery of the interfacial superconductivity (SC) of the Bi2Te3/Fe1+yTe heterostructure has attracted extensive studies due to its potential as a novel platform for trapping and controlling Majorana fermions. Here we present studies of another topological insulator (TI)/Fe1+yTe heterostructure, Sb2Te3/Fe1+yTe, which also has an interfacial 2-dimensional SC. The results of transport measurements support that reduction of the excess Fe concentration of the Fe1+yTe layer not only increases the fluctuation of its antiferromagnetic (AFM) order but also enhances the quality of the SC of this heterostructure system. On the other hand, the interfacial SC of this heterostructure was found to have a wider-ranging TI-layer thickness dependence than that of the Bi2Te3/Fe1+yTe heterostructure, which is believed to be attributed to the much higher bulk conductivity of Sb2Te3that enhances indirect coupling between its top and bottom topological surface states (TSSs). Our results provide evidence of the interplay among the AFM order, itinerant carries from the TSSs, and the induced interfacial SC of the TI/Fe1+yTe heterostructure system.

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Publisher's Note: Extremely large nonsaturating magnetoresistance and ultrahigh mobility due to topological surface states in the metallic Bi2Te3 topological insulator [Phys. Rev. B 95 , 195113 (2017)]

Physical Review B ◽

10.1103/physrevb.95.239901 ◽

2017 ◽

Vol 95 (23) ◽

Cited By ~ 5

Author(s):

K. Shrestha ◽

M. Chou ◽

D. Graf ◽

H. D. Yang ◽

B. Lorenz ◽

...

Keyword(s):

Topological Insulator ◽

Surface States ◽

Topological Surface

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Manifestation of axion electrodynamics through magnetic ordering on edges of a topological insulator

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1515664112 ◽

2015 ◽

Vol 112 (37) ◽

pp. 11514-11518 ◽

Cited By ~ 7

Author(s):

Yea-Lee Lee ◽

Hee Chul Park ◽

Jisoon Ihm ◽

Young-Woo Son

Keyword(s):

Electric Field ◽

Topological Insulator ◽

Time Reversal ◽

First Principles ◽

Surface States ◽

Magnetic Ordering ◽

Crystal Face ◽

Magnetic Dipoles ◽

Topological Surface ◽

The Difference

Because topological surface states of a single-crystal topological insulator can exist on all surfaces with different crystal orientations enclosing the crystal, mutual interactions among those states contiguous to each other through edges can lead to unique phenomena inconceivable in normal insulators. Here we show, based on a first-principles approach, that the difference in the work function between adjacent surfaces with different crystal-face orientations generates a built-in electric field around facet edges of a prototypical topological insulator such as Bi2Se3. Owing to the topological magnetoelectric coupling for a given broken time-reversal symmetry in the crystal, the electric field, in turn, forces effective magnetic dipoles to accumulate along the edges, realizing the facet-edge magnetic ordering. We demonstrate that the predicted magnetic ordering is in fact a manifestation of the axion electrodynamics in real solids.

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