Hikami Larkin Nagaoka Research Articles

Observation of surface dominated topological transport in strained semimetallic ErPdBi thin films

In this Letter, we present experimental observation of surface-dominated transport properties in [110]-oriented strained (∼1.6%) ErPdBi thin films. The resistivity data show typical semi-metallic behavior in the temperature range of 3 K ≤ T ≤ 350 K with a transition from semiconductor- to metal-like behavior below 3 K. The metallic behavior at low temperature disappears entirely in the presence of an external magnetic field >1 T. The weak-antilocalization (WAL) effect is observed in magneto-conductance data in the low magnetic field region and follows the Hikami–Larkin–Nagaoka (HLN) model. HLN fitting estimated single coherent channel, i.e., α ∼ −0.51 at 1.9 K, and the phase coherence length (Lϕ) shows the Lϕ ∼ T−0.52 power law dependence on temperature in the range of 1.9 K–10 K, indicating the observation of 2D WAL. Shubnikov–de Haas (SdH) oscillations are observed in magneto-resistance data below 10 K and are fitted to standard Lifhsitz Kosevich theory. Fitting reveals the effective mass of charge carriers ∼0.15 me and a finite Berry phase of 0.86π ± 0.16. The sheet carrier concentration and mobility of carriers estimated using SdH data are ns ∼ 1.35 × 1012 cm−2 and μs = 1210 cm2 V−1 s−1, respectively, and match well with the data measured using the Hall measurement at 1.9 K to be n ∼ 1.22 × 1012 cm−2, μ = 1035 cm2 V−1 s−1. These findings indicate the non-trivial nature and surface-dominated transport properties of strained (110) ErPdBi thin films at low temperatures.

Spin splitted topological surface states in PbBi4Te7

The most important feature in topological insulators is the conducting surface states that support back scattered prohibited transport of charge carriers. We report weak antilocalization (WAL) effect in mm size thick PbBi4Te7 single crystal, the transport evidence of the absence of back scattering of the charge carriers. Temperature dependency of phase coherence length is determined from modified Hikami–Larkin–Nagaoka (HLN) fitting of the WAL curves at different temperatures by considering electron–electron and electron–phonon interactions and the fitting parameters reveal two dimensional (2D) origin of the WAL effect, i.e. the presence of the topological surface states. Extracted Hikami pre-factor, α at different temperatures from the modified HLN fitting signifies that the top and bottom surface states in PbBi4Te7 are connected by bulk diffusive region. Shubnikov–de Haas (SdH) oscillations corroborate the presence of two Fermi surfaces DC1 and DC2 (deep buried one inside other) and non-trivial nature of which are confirmed from the observed -shift in Landau-levels fan diagram based on the SdH oscillations. Mobility (µ SdH ) values are determined from the Dingle analysis and are quite above the bulk mobility (µ) estimated from the low field Hall data, ascertaining the surface origin of the SdH oscillations. Surface Landé g-factors are determined from the observed peak splitting in SdH oscillations, attributed to the Zeeman effect and are 4.412 and 3.26 for DC1 and DC2, respectively, and are the consequence of strong spin–orbit coupling of the surface Dirac Fermions.

Weak Antilocalization Tailor-Made by System Topography in Large Scale Bismuth Antidot Arrays.

Using a two-carriers model and the Hikami-Larkin-Nagaoka (HLN) theory, we investigate the influence of large area patterning on magnetotransport properties in bismuth thin films with a thickness of 50 nm. The patterned systems have been produced by means of nanospheres lithography complemented by RF-plasma etching leading to highly ordered antidot arrays with the hexagonal symmetry and a variable antidot size. Simultaneous measurements of transverse and longitudinal magnetoresistance in a broad temperature range provided comprehensive data on transport properties and enabled us to extract the values of charge carrier densities and mobilities. Weak antilocalization signatures observed at low temperatures provided information on spin-orbit scattering length ranging from 20 to 30 nm, elastic scattering length of approx. 60 nm, and strong dependence on temperature phase coherence length. We show that in the absence of antidots the charge carrier transport follow 2-dimensional behavior and the dimensionality for phase-coherent processes changes from two to three dimensions at temperature higher than 10 K. For the antidot arrays, however, a decrease of the power law dephasing exponent is observed which is a sign of the 1D-2D crossover caused by the geometry of the system. This results in changes of scattering events probability and phase coherence lengths depending on the antidot diameters, which opens up opportunity to tailor the magnetotransport characteristics.

Quantum Transport Signatures of a Close Candidate for a Type II Nodal-Line Semimetal

The nodal-line semimetal is a new type of topological state of matter in which the crossing of two energy bands forms a nodal loop. In the absence of spin-orbit coupling, Mg3Bi2 is predicted as a type II nodal-line semimetal, which may evolve to a topological insulator with a small energy gap of ∼35 meV in the presence of spin-orbit coupling. However, the transport evidence is still lacking. Here, we measure the magneto-transport in Mg3Bi2. At low temperatures, the magnetoconductivity exhibits a weak antilocalization behavior. We fit the experimental data with a magnetoconductivity formula for the weak antilocalization effect of three-dimensional nodal-line semimetals as well as the well-known Hikami-Larkin-Nagaoka formula for two-dimensional weak (anti)localization effects. By comparing the fitting results of these two theories, we demonstrate that the weak antilocalization in Mg3Bi2 is better described by the theory for nodal-line semimetals. Our work will inspire more explorations to use the new weak localization theory to identify a large spectrum of nodal-line semimetals.

Evidence of weak antilocalization in quantum interference effects of (001) oriented La0.7Sr0.3MnO3–SrRuO3 superlattices

Quantum corrections to conductivity in the ferromagnetic La0.7Sr0.3MnO3 (LSMO) and SrRuO3 (SRO) thin films depend on the structural mismatches and interfaces accommodating ions and their spins. Here, by making interfaces of LSMO and SRO in the form of artificial superlattices, we achieve positive magnetoresistance (MR) and weak antilocalization (WAL), although the individual component shows negative MR and weak localization (WL). The [20 unit cell (u.c.) LSMO/3 u.c. SRO]×15 superlattice stabilizes in tetragonal symmetry associated with the rhombohedral and orthorhombic structures and demonstrates the occurrence of the single magnon scattering process. The low-field MR of the superlattice fit to the Hikami–Larkin–Nagaoka expression yields 595 Å phase coherence length (lϕ) with WAL of carriers. As the SRO layer thickness in the superlattice increases to 5 u.c., the value of lϕ = 292 Å decreases, and positive MR increases confirm the manifestation of WAL by SRO. The orthorhombic symmetry of the SRO is preserved in the [20 u.c. SRO/3 u.c. LSMO]×15 superlattice, which shows the existence of locally cooperative bond-length fluctuations and conduction due to the scattering of the electron by the Fermi liquid electrons, bond length, and spin fluctuations. However, as the LSMO layer thickness in the superlattice is increased to 5 u.c., the WL effect suppresses WAL at the low field. The spin–orbit coupling associated with magnetic anisotropy, i.e., spin and bond length fluctuations, modifies the WL in the superlattices and leads to WAL, thereby achieving positive MR.

Electrical Transport Properties of Vanadium‐Doped Bi2Te2.4Se0.6

Vanadium‐doped Bi2–xTe2.4Se0.6 single crystals, with x = 0.015 and 0.03, are grown by the Bridgman method. Bandstructure characterization by angle‐resolved photoemission spectroscopy (ARPES) measurements shows gapless topological surface states for both vanadium concentrations. The Van‐der‐Pauw resistivity, the Hall charge carrier density, and the mobility in the temperature range from 0.3 to 300 K are strongly dependent on vanadium concentration, with carrier densities as low as 1.5 × 1016 cm−3 and mobilities as high as 570 cm2 V−1s−1. As expected for transport in gapless topological surface states, the resistivity, carrier density, and mobility are constant below 10 K. The magnetoresistance shows weak antilocalization for both vanadium concentrations in the same temperature range. The weak antilocalization is analyzed with the Hikami–Larkin–Nagaoka model, which yields phase‐coherence lengths of up to 250 nm for x = 0.015.

Thickness-dependent magneto-transport properties of topologically nontrivial DyPdBi thin films

DyPdBi (DPB) is a topological semimetal which belongs to the rare-earth-based half-Heusler alloy family. In this work, we studied the thickness-dependent structural and magneto-transport properties of DPB thin films (20 to 60 nm) grown using pulsed laser deposition. The DPB thin films show (110) oriented growth on MgO(100) single crystal substrates. Longitudinal resistance data indicate metallic surface states dominated carrier transport and the suppression of semiconducting bulk state carriers for films ≤40 nm. We observe the weak antilocalization (WAL) effect and Shubnikov–de Hass (SdH) oscillations in the magneto-transport data. The presence of a single coherent transport channel (α∼ −0.50) is observed in the Hikami–Larkin–Nagaoka (HLN) fitting of WAL data. The power law temperature dependence of phase coherence length (LØ) ∼ T−0.50 indicates the observation of the 2D WAL effect and the presence of topological nontrivial surface states for films ≤40 nm. The 60 nm sample shows semiconducting resistivity behavior at higher temperature (>180 K) and HLN fitting results (α∼ −0.72, LØ∼ T−0.68) indicate the presence of partial decoupled top and bottom surface states. The Berry phase ∼π is extracted for thin films ≤40 nm, which further demonstrates the presence of Dirac fermions and nontrivial surface states. Band structure parameters are extracted by fitting SdH data to the standard Lifshitz–Kosevich formula. The sheet carrier concentration and cyclotron effective mass of carriers decrease with increasing thickness (20 nm to 60 nm) from ∼1.35 × 1012 cm−2 to 0.68 × 1012 cm−2 and from ∼0.26 me to 0.12 me, respectively. Our observations suggest that samples with a thickness ≤40 nm have transport properties dominated by surface states and samples with a thickness ≥60 nm have contributions from both bulk and surface states.

Magnetotransport properties of noncentrosymmetric CaAgBi single crystal

We report on the single crystal growth and transport properties of a topological semimetal CaAgBi which crystallizes in the hexagonal ABC-type structure with the non-centrosymmetric space group P63mc (No. 186). The transverse magnetoresistance measurements with current in the basal plane of the hexagonal crystal structure reveal a value of about 30% for I∥[10̄0] direction and about 50% for I∥[1̅10] direction at 10 K in an applied magnetic field of 14 T. The magnetoresistance shows a cusp-like behavior in the low magnetic field region, suggesting the presence of weak antilocalization effect for temperatures less than 100 K. The Hall measurements reveal that predominant charge carriers are p-type, exhibiting a linear behavior at high fields. The magnetoconductance of CaAgBi is analyzed based on the modified Hikami–Larkin–Nagaoka model. Our first-principle calculations within a density-functional theory framework reveal that the Fermi surface of CaAgBi consists of both the electron and hole pockets and the size of the hole pocket is much larger than electron pockets suggesting the dominant p-type carriers in accordance with our experimental results.

The temperature dependence of anomalous magnetoresistance and weak antilocalization in HgTe/CdTe (111) quantum wells

The temperature dependence of anomalous magnetoresistance and weak antilocalization (WAL) is studied in HgTe/CdTe (111) quantum wells (QWs). An anomalous positive to negative magnetoresistance transformation dependent on temperature is observed in HgTe/CdTe QWs grown at 157 °C, but not in those grown at 160 °C. The Hikami–Larkin–Nagaoka model is employed to analyze the WAL effect. A high-resolution transmission electron microscopy investigation of the HgTe–CdTe interface supports the transport results. For HgTe topological insulators, the anomalous magnetoresistance may be caused by temperature-induced fluctuations in conduction, which could transform the inverted energy band to a normal energy band. At high temperature, the negative magnetoresistance may be due to scattering of the interface defective states under the normal energy band.

Surface characterization and magneto-transport study on $$\hbox {Bi}_2\hbox {Te}_2\hbox {Se}$$ topological insulator thin film

Topological insulators (TIs) a new quantum state of matter predicted to have an interesting surface properties. In this report, we study the surface properties of $$\hbox {Bi}_2\hbox {Te}_2\hbox {Se}$$ (BTS) topological insulators thin films. Raman measurements on BTS thin film show a strong intensity of $$\hbox {A}{^1}_{1\text {g}}$$ ($$\sim 62\hbox { cm}{^{-1}}$$), $$\hbox {E}{^2}_\text {g}$$ ($$\sim 123\hbox { cm}{^{-1}}$$) and $$\hbox {A}{^2}_{1\text {g}}$$ ($$\sim 170\hbox { cm}{^{-1}}$$) modes in addition to $$\hbox {A}{^2}_{1\text {u}}$$ ($$\sim 140\hbox { cm}{^{-1}}$$) modes. Elemental analyses were done using X-ray photoelectron spectroscopy (XPS). Resistance versus temperature measurement reveal a magnetic field-driven metallic behavior at high temperatures and further analysis on magnetic measurement shows a diamagnetic nature of BTS film. The magneto-resistance measurements on these films exhibit a weak antilocalization effect that arises due to quantum interfering nature of topological insulators and the measured weak anti-localization effect is fitted using Hikami–Larkin–Nagaoka (HLN) model.

Experimental Evidence of Topological Surface States in Mg3Bi2 Films Grown by Molecular Beam Epitaxy**Supported by the Science Challenge Project under Grant No TZ2016004, the Opening Foundation of State Key Laboratory of High Performance Computing under Grant No 201601-02, the Foundation of President of CAEP under Grant No 201501040, the Natural Science Foundation of Hunan Province under Grant No 2016JJ1021, the

Nodal line semimetal (NLS) is a new quantum state hosting one-dimensional closed loops formed by the crossing of two bands. The so-called type-II NLS means that these two crossing bands have the same sign in their slopes along the radial direction of the loop, which requires that the crossing bands are either right-tilted or left-tilted at the same time. According to the theoretical prediction, Mg3Bi2 is an ideal candidate for studying the type-II NLS by tuning its spin-orbit coupling (SOC). High-quality Mg3Bi2 films are grown by molecular beam epitaxy (MBE). By in-situ angle resolved photoemission spectroscopy (ARPES), a pair of surface resonance bands around the point are clearly seen. This shows that Mg3Bi2 films grown by MBE are Mg(1)-terminated by comparing the ARPES spectra with the first principles calculations results. Moreover, the temperature dependent weak anti-localization effect in Mg3Bi2 films is observed under magneto-transport measurements, which shows clear two-dimensional (2D) e–e scattering characteristics by fitting with the Hikami–Larkin–Nagaoka model. Therefore, by combining with ARPES, magneto-transport measurements and the first principles calculations, this work proves that Mg3Bi2 is a semimetal with topological surface states. This paves the way for Mg3Bi2 to be used as an ideal material platform to study the exotic features of type-II nodal line semimetals and the topological phase transition by tuning its SOC.

Weak antilocalization in Sb2Te3 nano-crystalline topological insulator

Microwave-assisted solvothermal route has been followed to synthesize Sb2Te3 nanomaterial. The morphology and topography of the material have been studied in FESEM and AFM measurements respectively. The optical band gap of the material is found to be ~ 0.25 eV as measured in IR spectroscopy. Temperature dependent resistivity of the nanostructure shows thermal activation behavior in the high temperature region as well as it follows 3D Variable Range Hopping mechanism in the moderate temperature region. Electron-electron interaction and quantum interference dominated upturn in the resistivity is observed at T < 24 K. Low field magnetoconductivity (MC) shows disorder induced weak localization (WL) which makes over to weak antilocalization (WAL) at T ≥ 4 K. MC after post annealing of the sample shows WAL behavior at T < 4 K also. Quantum correction to the low field magnetoconductivity of the material follows Hikami-Larkin-Nagaoka (HLN) equation. The obtained parameters of the HLN equation indicate that the system follows the 2D conduction mechanism and presence of a single conduction channel at low temperature. High field MR exhibits linear and positive magnetoresistance (LPMR) which suggests the survival of robust topological surface state conduction in the nanostructured bulk Sb2Te3 topological insulator.

Flux free single crystal growth and detailed physical property characterization of Bi1−xSbx (x = 0.05, 0.1 and 0.15) topological insulator

Here, we report the crystal growth, physical and transport properties of Bi1−xSbx (x = 0.05, 0.1 and 0.15) topological insulator. Single crystals of Bi1-xSbx (x = 0.05, 0.1 and 0.15) were grown by melting bismuth and antimony together using the facile self flux method. The XRD measurements displayed highly indexed 00l lines and confirmed the crystalline nature as well as the rhombohedral structure of the Bi1-xSbx (x = 0.05, 0.1 and 0.15) crystals. Raman spectroscopy measurements for Bi1-xSbx system revealed four peaks within the spectral range of 10 to 250 cm−1 namely A1g and Eg modes corresponding to Bi-Bi and Sb-Sb vibrations. Scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX) measurements showed the layered surface morphology and near stoichiometric chemical composition of Bi1-xSbx (x = 0.05, 0.1 and 0.15) crystals. Furthermore, EDAX mapping confirmed the homogeneous distribution of Bi and Sb elements. Temperature dependent electrical resistivity curves with and without applied magnetic field exhibited a metallic behaviour and linear non-saturating magneto-resistance (MR) respectively for all the antimony (Sb) concentrations of x = 0.05, 0.1 and 0.15. The lowest Sb concentration sample with x = 0.05 (Bi0.95Sb0.05) exhibited the highest MR value of about 1400%, followed by x = 0.1 and 0.15 samples (Bi0.9Sb0.1 and Bi0.85Sb0.05) with MR values reaching up to 500% and 110% respectively at 2 K and 6Tesla applied field. Also, a coexistence of negative MR and WAL/WL behaviour is observed at lower magnetic fields (below ±0.2Tesla) in Bi0.9Sb0.1 and Bi0.85Sb0.05 system. To further elaborate the transport properties of Bi1-xSbx (x = 0.05, 0.1 and 0.15), the magneto-conductivity (MC) is fitted to the HLN (Hikami Larkin Nagaoka) equation and it is found that the charge conduction mechanism is mainly dominated by WAL (weak anti-localization) along with a small contribution from WL (weak localization) effect. Summarily, the short letter discusses the synthesis, interesting transport and magneto-transport properties of Bi1-xSbx (x = 0.05, 0.1 and 0.15), which could be useful in understanding the fascinating properties of topological insulators and their technological applications.

Structural, surface morphology and magneto-transport properties of self flux grown Eu doped Bi2Se3 single crystal

Here, we report the effect of europium (Eu) doping in Bi2Se3 topological insulator (TI) by using different characterization techniques viz. X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDXA) and magneto-transport measurements. Good quality Eu doped Bi2Se3 (Eu0.1Bi1.9Se3) single crystal is grown by the self flux method through the solid state reaction route. Single crystal XRD pattern displayed the high crystalline quality of the Eu0.1Bi1.9Se3 sample along (00l) alignment whereas; the powder XRD confirmed the rhombohedral crystal structure without any impurity phases. SEM images exhibited a layered slab like structure stacked one over the other whereas; EDXA measurements confirmed the chemical composition of Eu0.1Bi1.9Se3 sample. Further, the EDXA mapping showed the homogeneous distribution of Bi, Se and Eu elements. Temperature dependent electrical resistivity curves revealed a metallic behaviour both in the presence and absence of applied magnetic field. Magneto-transport measurements showed a decrease in the magneto-resistance (MR) value of the Eu0.1Bi1.9Se3 sample (∼32% at 5 K) in comparison to the pure Bi2Se3 sample (∼80% at 5 K). For, Eu0.1Bi1.9Se3 sample, a complex crossover between WL and WAL phenomenon was observed at lower applied magnetic fields, whereas the same was absent in case of the pristine one. Further, HLN (Hikami Larkin Nagaoka) fitted magneto-conductivity (MC) analysis revealed a competing weak anti localization (WAL) and weak localization (WL) behaviour. Summarily, in the present work we study the structural, surface morphology and magneto-transport properties of as grown Eu0.1Bi1.9Se3 single crystals.

Quasi-2D Transport and Weak Antilocalization Effect in Few-layered VSe2.

With strong spin-orbit coupling (SOC), ultrathin two-dimensional (2D) transitional metal chalcogenides (TMDs) are predicted to exhibit weak antilocalization (WAL) effect at low temperatures. The observation of WAL effect in VSe2 is challenging due to the relative weak SOC and three-dimensional (3D) transport nature in thick VSe2. Here, we report on the observation of quasi-2D transport and WAL effect in sublimed-salt-assisted low-temperature chemical vapor deposition (CVD) grown few-layered high-quality VSe2 nanosheets. The WAL magnitudes in magnetoconductance can be perfectly fitted by the 2D Hikami-Larkin-Nagaoka (HLN) equation in the presence of strong SOC, by which the spin-orbit scattering length lSO and phase coherence length lϕ have been extracted. The phase coherence length lϕ shows a power law dependence with temperature, lϕ∼T-1/2, revealing an electron-electron interaction-dominated dephasing mechanism. Such sublimed-salt-assisted growth of high-quality few-layered VSe2 and the observation of WAL pave the way for future spintronic and valleytronic applications.

Growth, Characterization and High-Field Magneto-Conductivity of Co0.1Bi2Se3 Topological Insulator

We report the crystal growth as well as transport properties of Co added Bi2Se3 (Co0.1Bi2Se3) single crystals. The values of the lattice parameters for pure and Co added sample were nearly the same. The Raman spectroscopy displayed slightly higher Raman shift of corresponding A1g1, Eg2, and A1g2 vibrational modes for Co0.1Bi2Se3, and the resistivity curves with and without applied magnetic field show a metallic behavior. Both the crystals were subjected to magneto-resistance (MR) measurements under applied fields of 14 T. The value of MR is found to decrease from about 380% (5 K, 14 T) for Bi2Se3 to 200% for Co0.1Bi2Se3. To elaborate the transport properties of pure and Co added Bi2Se3 crystals, the magneto-conductivity is fitted to the HLN (Hikami-Larkin-Nagaoka) equation, and it is found that the charge conduction is mainly dominated by surface-driven WAL (weak anti-localization) with negligible bulk WL (weak localization) contribution in both crystals alike. The MH curves of Co0.1Bi2Se3 crystal at different temperatures displayed a combination of both ferromagnetic and diamagnetic behavior. On the other hand, the electron paramagnetic resonance (EPR) revealed that pure Bi2Se3 is diamagnetic, whereas Co orders ferromagnetically with resonating field around 3422 Oe at room temperature. The calculated value of Lande “g” factor is around 2.04 ± 0.05. Summarily, the short letter discusses the interesting magneto-conductivity and complex magnetism of Co in Co0.1Bi2Se3.

Magneto-transport and weak anti-localization in ferromagnetic semiconductor CrSiTe3 single crystal

The temperature dependence of resistance of CrSiTe3 single crystals shows a cusp below the Cure temperature, which may be attributed to the disappearance of electron scattering on magnetic fluctuation. The magneto-conductance of CrSiTe3 was measured at temperatures ranging from 50 K to 30 K over the magnetic field range of 0–5 T. Magneto-transport measurements demonstrate that the low-field negative magneto-conductivity results from the weak anti-localization (WAL). The WAL effect was analyzed based on the Hikami-Larkin-Nagaoka (HLN) two-dimensional (2D) diffusive transport theory and the HLN equation could well fit the magneto-conductivity data.

High-Field Magneto-Conductivity Analysis of Bi2Se3 Single Crystal

We report the high field (up to 14Tesla) magneto-conductivity analysis of Bi2Se3 topological insulator grown via the self flux method. The detailed experimental investigations including crystal growth as well as the electrical, thermal and spectroscopic characterizations of the resultant Bi2Se3 single crystal are already reported by some of us. The current letter deals with high field magneto-conductivity analysis in terms of Hikami Larkin Nagaoka (HLN) model, which revealed that the electronic conduction is dominated by both surface states driven weak anti localization (WAL), as well the bulk WL (weak localization) states. Further, by applying the HLN equation we have extracted the fitting parameters i.e., phase coherence length and the pre-factor. The HLN equation exhibited values of [pre factor close to -1.0, indicating both WAL and WL contributions. On the other hand, the extracted phase coherence length is seen to decrease from 11.125 nm to 5.576 nm as the temperature is increased from 5K to 200K respectively. Summarily, the short letter discusses primarily the temperature dependent magneto-conductivity analysis of pristine Bi2Se3 single crystal by the HLN model.

Weak Antilocalization and Quantum Oscillations of Surface States in Topologically Nontrivial DyPdBi(110)Half Heusler alloy

Recently, a number of ternary half-Heusler compounds have been predicted independently by several research groups as candidates for 3D topological insulators. In this work, we report the observation of a two-dimensional (2D) weak antilocalization (WAL) effect, one of the hall-marks of topological surface states, and Shubnikov-de Hass (SdH) quantum oscillations in <110> oriented DyPdBi (DPB) thin films grown on MgO (100) substrates. The films prepared by pulsed laser deposition technique under the optimized conditions, showed a textured structure with (110) planes parallel to the (100) plane of MgO. The measured WAL effect follows the Hikami-Larkin-Nagaoka (HLN) model and the extracted values of phase coherence length (lϕ) and α are ~420 nm and ~−0.52 respectively. The power law variation of lϕ (~T−0.46) indicates the presence of the 2D surface states in DPB film. The Dirac nature of the surface states is further confirmed by Landau-level fan diagram analysis of SdH oscillations of the magneto-transport data. This analysis shows a finite Berry phase of 0.90π ± 0.16, reasonably close to the expected π value. Sheet Carrier density, ns ~ 2.56 × 1012 cm−2, calculated from the SdH oscillations (fSdH ~ 106 T) and Hall measurements agree well with each other. These findings demonstrate that the half Heusler DPB thin films (~15–20 nm) can be used as a suitable material for investigating the novel intrinsic quantum transport properties of surface Dirac fermions.

Weak localization in bilayer graphene with Li-intercalation/desorption

We performed in-situ electrical transport measurements for bilayer graphene grown on SiC(0 0 0 1) substrate, Li-intercalated bilayer graphene, and after that desorbing Li atoms by heating. Bilayer graphene after desorbing intercalated Li atoms showed a higher resistivity and different behavior in magnetoconductance compared to pristine bilayer graphene. We observed the weak localization of carriers at low temperatures in all the three samples and analyzed the experimental results with the extended Hikami–Larkin–Nagaoka equation to investigate the transport properties. The result shows that the magnetoconductance of pristine bilayer graphene is described by the AB stacking structure model and the phase breaking scattering is dominated by the electron–electron scattering. The intra-valley scattering occurs most frequently probably due to dopants in SiC substrate. However, in Li-desorbed graphene, the magnetoconductance can be described by neither AB nor AA-stacking model, suggesting the coexistence of domains with several different stacking structures.