Large linear magnetoresistance and weak anti-localization in Y (Lu) PtBi topological insulators (original) (raw)
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Electronic structure and linear magnetoresistance of the gapless topological insulator PtLuSb
The present work reports on the experimental investigation of electronic structure and transport properties of the proposed topological insulator PtLuSb. The electronic structure was investigated by means of polarization dependent hard x-ray photoelectron spectroscopy. The valence band spectra exhibit a linear behavior close to the Fermi energy, as is typical for massless electrons. The transport properties are similar to that of a gapless semiconductor with low carrier concentration. This compound also exhibits an exceptionally high Hall mobility. At low temperatures, the magnetoresistance changes linearly with the applied magnetic field, whereas it exhibits a quadratic nature at high temperatures. A tentative relation between linear magnetoresistance and high mobility is discussed. V C 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4730387\]
Magnetotransport and induced superconductivity in Bi based three-dimensional topological insulators
physica status solidi (RRL) - Rapid Research Letters, 2012
The surface of a 3D topological insulator is conducting and the topologically nontrivial nature of the surface states is observed in experiments. It is the aim of this paper to review and analyze experimental observations with respect to the magnetotransport in Bi-based 3D topological insulators, as well as the superconducting transport properties of hybrid structures consisting of superconductors and these topological insulators. The helical spin-momentum coupling of the surface state electrons becomes visible in quantum corrections to the conductivity and magnetoresistance oscillations. An analysis will be provided of the reported magnetoresistance, also in the presence of bulk conductivity shunts. Special attention is given to the large and linear magnetoresistance. Superconductivity can be induced in topological superconductors by means of the proximity effect. The induced supercurrents, Josephson effects and current-phase relations will be reviewed. These materials hold great potential in the field of spintronics and the route towards Majorana devices.
Physical Review B, 2013
We report superconductivity in the ternary half-Heusler compound LuPtBi, with Tc = 1.0 K and Hc2 = 1.6 T. The crystal structure of LuPtBi lacks inversion symmetry, hence the material is a noncentrosymmetric superconductor. Magnetotransport data show semimetallic behavior in the normal state, which is evidence for the importance of spin-orbit interaction. Theoretical calculations indicate that the strong spin-orbit interaction in LuPtBi should cause strong band inversion, making this material a promising candidate for 3D topological superconductivity. 74.25.fc, 71.20.E, 71.30.+h I.
Science Advances, 2015
We report superconductivity and magnetism in a new family of topological semimetals, the ternary half Heusler compounds RPdBi (R : rare earth). In this series, tuning of the rare earth f -electron component allows for simultaneous control of both lattice density via lanthanide contraction, as well as the strength of magnetic interaction via de Gennes scaling, allowing for a unique tuning of both the normal state band inversion strength, superconducting pairing and magnetically ordered ground states. Antiferromagnetism with ordering vector (0.5,0.5,0.5) occurs below a Néel temperature that scales with de Gennes factor dG, while a superconducting transition is simultaneously linearly suppressed. With superconductivity appearing in a system with non-centrosymmetric crystallographic symmetry, the possibility of spin-triplet Cooper pairing with non-trivial topology analogous to that predicted for the normal state electronic structure provides a unique and rich opportunity to realize both predicted and new exotic excitations in topological materials.
Scientific reports, 2014
A large number of half-Heusler compounds have been recently proposed as three-dimensional (3D) topological insulators (TIs) with tunable physical properties. However, no transport measurements associated with the topological surface states have been observed in these half-Heusler candidates due to the dominating contribution from bulk electrical conductance. Here we show that, by reducing the mobility of bulk carriers, a two-dimensional (2D) weak antilocalization (WAL) effect, one of the hallmarks of topological surface states, was experimentally revealed from the tilted magnetic field dependence of magnetoconductance in a topologically nontrivial semimetal LuPdBi. Besides the observation of a 2D WAL effect, a superconducting transition was revealed at Tc ~ 1.7 K in the same bulk LuPdBi. Quantitative analysis within the framework of a generalized BCS theory leads to the conclusion that the noncentrosymmetric superconductivity of LuPdBi is fully gapped with a possibly unconventional ...
Large surface conductance and superconductivity in topological insulator microstructures
Applied Physics Letters
Controllable geometric manipulation via micromachining techniques provides a promising tool for enhancing useful topological electrical responses relevant to future applications such as quantum information science 1-4. Here we present microdevices fabricated with focused ion beam from indium-doped topological insulator Pb1-xSnxTe. With device thickness on the order of 1 μm and an extremely large bulk resistivity, we achieve an unprecedented enhancement of the surface contribution to about 30% of the total conductance near room temperature. The surface contribution increases as the temperature is reduced, becoming dominant below approximately 180 K, compared to 30 K in mmthickness crystals. In addition to the enhanced surface contribution to normal-state transport, we observe the emergence of surface superconductivity below 6 K. Measurements of magnetoresistivity at high magnetic fields reveal a weak antilocalization behavior in the normal-state magnetoconductance at low temperature and a variation in the power-law dependence of resistivity on temperature with field. These results demonstrate that interesting electronic responses relevant to practical applications can be achieved by suitable engineering of single crystals. Tunable electrical responses and the emergence of superconductivity in topological insulators have garnered broad interest in both academic and industrial communities due to their potential applications 5,6. Three-dimensional topological crystalline insulators, with an inverted bulk band gap and spin-momentum-locked metallic surface states protected by crystalline symmetry, represent a useful quantum state of matter 6-9. Theoretically, such topological crystalline insulators have been predicted for the rocksalt crystal structure 7,8,10. Subsequent photoemission spectroscopy measurements of Pb1-xSnxTe observed Dirac states near high-symmetry reciprocal lattice points 11-14. Pb1-xSnxTe features a topological phase transition with doping x and hosts nontrivial surface states for x larger than ~ 0.35 12,14. By compensating for defects with In substitution, the bulk resistivity of Pb1-xSnxTe can be unusually large for intermediate x 14,15. Surprisingly, a slightly higher In concentration can lead to the emergence of superconductivity 16. As the resistivity of In-doped Pb1-xSnxTe is approximately two orders of magnitude greater than that of the most dilute superconductors (e.g., Ca-doped SrTiO3) 15,17 , the nature of superconductivity in Pb1-xSnxTe is at odds with conventional Bardeen-Cooper-Schrieffer theory 18 .
Possible transport evidence for three-dimensional topological superconductivity in doped β-PdBi2
Scientific Reports
interest in topological states of matter burgeoned over a decade ago with the theoretical prediction and experimental detection of topological insulators, especially in bulk three-dimensional insulators that can be tuned out of it by doping. their superconducting counterpart, the fully-gapped threedimensional time-reversal-invariant topological superconductors, have evaded discovery in bulk intrinsic superconductors so far. the recently discovered topological metal β-pdBi 2 is a unique candidate for tunable bulk topological superconductivity because of its intrinsic superconductivity and spinorbit-coupling. in this work, we provide experimental transport signatures consistent with fullygapped 3D time-reversal-invariant topological superconductivity in K-doped β-pdBi 2. in particular, we find signatures of odd-parity bulk superconductivity via upper-critical field and magnetization measurements-odd-parity pairing can be argued, given the band structure of β-pdBi 2 , to result in 3D topological superconductivity. in addition, Andreev spectroscopy reveals surface states protected by time-reversal symmetry which might be possible evidence of Majorana surface states (Majorana cone). Moreover, we find that the undoped bulk system is a trivial superconductor. Thus, we discover β-pdBi 2 as a unique bulk material that, on doping, can potentially undergo an unprecedented topological quantum phase transition in the superconducting state. According to the traditional Landau-Ginzburg paradigm, states of matter are defined by the symmetries broken in thermal equilibrium that are preserved by the underlying Hamiltonian, and phase transitions acquire universal features that only depend on the symmetries involved and the spatial dimension. However, this definition proves inadequate for topological phases, in which the ground state wavefunction of the bulk system is characterized by a global, topological quantum number which distinguishes it from a conventional phase with the same symmetries 1-3. Naturally, critical points separating these phases fall outside the traditional paradigm as well. The most striking consequence of the non-trivial bulk topology is the presence of robust surface states where the bulk terminates. One of the most celebrated topological phases in condensed matter systems is the time-reversal symmetric strong topological insulator (TI) in three dimensions, which is characterized by a Z 2 topological invariant ν = odd/even 4,5. The surface manifestation of the bulk topology in this phase is the presence of an odd number of pseudo-relativistic, helical surface states (Dirac Cone) that are robust against non-magnetic perturbations. Numerous materials have been predicted to be in this phase, and many of them have been experimentally confirmed. Additionally, several TIs can be tuned into trivial insulators with doping, thus allowing experimental access to the quantum critical point separating them. A close cousin of the topological insulator is the time-reversal symmetric topological superconductor (TSC) in 3D (Class 3D III) 2. Here, the superconducting gap plays the role of the insulating gap of the insulator, the topological invariant is ν ∈ = … Z 0, 1, 2 , and the surface hosts ν helical Majorana fermions (Majorana cone) instead of Dirac fermions (Dirac Cone). The sufficient conditions for 3D time-reversal invariant (TRI) topological superconductivity are: One, the normal state Fermi surfaces enclose an odd number of time-reversal invariant momenta, two, the bulk superconductivity is fully gapped, and three, odd-parity 6,7. Once these conditions are met, the surface states are spanned by robust, helical Majorana surface states. The 2D Majorana surface states also referred to as the Majorana cone (can be regarded as the superconducting analog of the 2D Dirac cone)-and is distinct from the Majorana Zero Mode (MZM). The transport signatures of 2D Majorana surface states are also
Experimental Verification of PbBi_{2}Te_{4} as a 3D Topological Insulator
Physical Review Letters, 2012
We show the first experimental evidence of the topological insulator phase in PbBi2Te4 accompanying a single surface Dirac cone by angle-resolved photoemission spectroscopy (ARPES) with synchrotron radiation. Theoretically it has turned out to have a Z2 topological invariant 1; (111). The observed two-dimensional iso-energy contours in the bulk energy gap region are found to be the largest among the other 3D topological insulators established ever. This opens a pathway to realizing the quantum topological transport with a sufficiently large spin current density. PACS numbers: 73.20.-r, 79.60.-i
Electronic transport properties of topological insulators and low dimensional superconductors
Scientia Sinica Physica, Mechanica & Astronomica, 2013
In this review, we present a summary of some recent experiments on topological insulators (TIs) and superconducting nanowires and films. Electron-electron interaction (EEI), weak anti-localization (WAL) and anisotropic magneto-resistance (AMR) effect found in TI films by transport measurements are reported. Then, transport properties of superconducting films, bridges and nanowires and proximity effect in non-superconducting nanowires are described. Finally, the interplay between TIs and superconductors (SCs) is also discussed.