Search

Strain influence on the longitudinal magnetoresistance for the n-type conductivity InSb whiskers doped by Sn to concentration 6·10¹⁶–6·10¹⁷ сm⁻³ was studied in the temperature range 4.2–40 K and magnetic field up to 10 T. The Shubnikov–de Haas oscillations at low temperatures were observed in the strained and unstrained samples in all range of doping concentrations and magnetic fields. The character of longitudinal magnetoresistance dependences was analyzed and compared with theoretical one. The whisker magnetoresistance alters its sign with increasing magnetic field. It is positive at weak magnetic fields and becomes negative at higher magnetic fields. Possible mechanism of the large value of negative magnetoresistance (NMR) was discussed in the InSb whiskers with doping concentration in the vicinity to metal–insulator transition. The origin of large NMR was explained by the existence of classical size effect and boundary scattering during conductance in subsurface whisker layers. На основі досліджень поздовжнього магнітоопору ниткоподібних кристалів InSb n-типу провідності, легованих Sn до концентрацій 6·10¹⁶–6·10¹⁷ см⁻³ , в інтервалі температур 4,2– 40 К і магнітних полів до 10 Тл виявлено осциляції Шубнікова–де Гааза в деформованих і недеформованих зразках. Проведено аналіз поведінки польових залежностей магнітоопору згідно відомих теоретичних уявлень. Встановлено, що з підвищенням індукції магнітного поля магнітоопір ниткоподібних кристалів InSb змінює свій знак від позитивного до від’ємного. Обговорюються механізми, які зумовлюють появу високих значень від’ємного магнітоопору (ВМО) у зразках InSb з концентрацією легуючої домішки, що відповідає близькості до переходу метал–діелектрик. Існування ВМО пов’язане з класичним розмірним ефектом, а також гранічним розсіюванням у провідності приповерхневих шарів мікрокристалів. На основе исследований продольного магнитосопротивления нитевидных кристаллов InSb n-типа проводимости, легированных Sn до концентраций 6·10¹⁶–6·10¹⁷ см⁻³ , в интервале температур 4,2–40 К и магнитных полей до 10 Тл обнаружены осцилляции Шубникова–де Гааза в деформированных и недеформированных образцах. Проведен анализ поведения полевых зависимостей магнитосопротивления согласно известным теоретическим представлениям. Установлено, что с повышением индукции магнитного поля магнитосопротивление нитевидных кристаллов InSb меняет свой знак от положительного к отрицательному. Обсуждаются механизмы, которые обусловливают появление высоких значений отрицательного магнитосопротивления (ОМС) в образцах InSb с концентрацией легирующей примеси, соответствующей близости к переходу металл–диэлектрик. Существование ОМС обусловлено классическим размерным эффектом, а также граничным рассеиванием в проводимости приповерхностных слоев микрокристаллов.

This dissertation summarizes my work on the study of topological insulators, graphene, and transition metal dichalcogenides, especially on the electrical transport studies. There are mainly two parts in this dissertation. The first part is the study on topological insulators. Bi2Se3 and Bi2Te2Se single crystals are synthesized and characterized. Calcium dopants are introduced to Bi2Se3 to compensate for the excess electrons generated by selenium vacancies in the as-grown single crystals. An n- to p-type transition is then realized. The bulk insulating state is achieved. In Bi2Te2Se bulk samples, extremely high low-temperature resistivity (> 2 Ohm cm) is achieved. Nanodevices of Bi2Se3 and Bi2Te2Se are then fabricated. A lithography-free technique is developed for device fabrication in order to well maintain the pristine state of bulk samples. Electron beam irradiation is performed to manually adjust the Fermi levels in the devices. Further control of the Fermi level is realized with the application of gate voltages. The insulating temperature behavior is achieved in devices upon electron beam irradiation. And the gate modulation grows as the electron beam irradiation dosage increases. The field-effect mobility is greatly enhanced and a ten-fold increase is obtained. The second part is focused on graphene and transition metal dichalcogenides. Graphene is expected to exhibit ferromagnetism induced by the magnetic proximity effect when it is placed on a magnetic material. With enhanced spin-orbit coupling, the anomalous Hall effect can be realized in graphene. Meanwhile, a topological gap is opened at the Dirac point, making it possible to realize the quantized anomalous Hall effect when the Fermi level is in the gap. In this dissertation, graphene devices are transferred to yttrium iron garnet thin films, a ferrimagnetic material. At low temperatures, anomalous Hall effect is observed. Further studies on the temperature dependence and gate dependence of the anomalous Hall effect is performed. For single-layer MoS2, at the valence band maxima, the band is split by 160 meV due to strong spin-orbit coupling. Spin-up and spin-down electrons reside in different bands due to the broken inversion symmetry. Valley and spin degrees of freedom of the valence bands are inherently coupled in single-layer MoS2. It is an ideal material to study the valley Hall effect.

We report an investigation of the combined structural and electronic properties of the bronze Na 1.5 ( PO 2 ) 4 ( WO 3 ) 20 . Its low-dimensional structure and possible large reconstruction of the Fermi surface due to charge density wave instability make this bulk material a natural superlattice with a reduced number of carriers and Fermi energy. Signatures of multilayered two-dimensional (2D) electron weak localization are consequently reported, with an enhanced influence of quantum oscillations. A crossover between these two antagonistic entities, previously observed only in genuine low-dimensional materials and devices, is shown to occur in a bulk crystal due to its hidden 2D nature., A.P. would like to thank Thierry Klein and Andrea Gauzzi for valuable remarks on the competition between weak localization and quantum oscillation conditions which motivated our analysis. Financial support by the ANR Projects No. ANR-18-CE92-0014 and No. ANR-11-BS04- 0004 is gratefully acknowledged. Work in Spain was supported by MICIU (PGC2018-096955-B-C44 and PGC2018- 093863-B-C22), MINECO through the Severo Ochoa (SEV2015-0496) and Maria de Maeztu (MDM-2017-0767) Programs, and the Generalitat de Catalunya (2017SGR1506 and 2017SGR1289). E.D.-N. was supported by the project NanoCent-Nanomaterials center for advanced applications, Project No. CZ.02.1.01/0.0/0.0/15_003/0000485, financed by the ERDF.

We have used the envelope function formalism to investigate the bands structure of LWIR type II SL InAs (d1 = 2. 18d2)/In0.25Ga0.75Sb(d2 = 21.5 Å). Thus, we extracted optical and transport parameters as the band gap, cut off wavelength, carriers effective mass, Fermi level and the density of state. Our results show that the higher optical cut-off wavelength can be achieved with smaller layer thicknesses. The semiconductor-semi metal transition was studied as a function of temperature. Our results permit us the interpretations of Hall and Shubnikov-de Haas effects. These results are in agreement with experimental results in literature and a guide for engineering infrared detectors.

Unambiguous and complete determination of the Fermi surface is a primary step in understanding the electronic properties of topical metals and semi-metals, but only in a relatively few cases has this goal been realized. In this work, we present a systematic high-field quantum oscillation study up to 35 T on ZrSiS, a textbook example of a nodal-line semimetal with only linearly dispersive bands crossing the Fermi energy. The topology of the Fermi surface is determined with unprecedented precision and all pockets are identified by comparing the measured angle dependence of the quantum oscillations to density functional theory calculations. Comparison of the Shubnikov-de Haas and de Haas-van Alphen oscillations at low temperatures and analysis of the respective Dingle plots reveal the presence of significantly enhanced scattering on the electron pocket. Above a threshold field that is aligned along the c-axis of the crystal, the specific cage-like Fermi surface of ZrSiS allows for electron-hole tunneling to occur across finite gaps in momentum space leading to quantum oscillations with a complex frequency spectrum. Additional high-frequency quantum oscillations signify magnetic breakdown orbits that encircle the entire Dirac nodal loop. We suggest that the persistence of quantum oscillations in the resistivity to high temperatures is caused by Stark interference between orbits of nearly equal masses., Comment: 14 pages, 13 figures

We have developed a unified analytical model for computation of 2D electron gas sheet charge density in AlInN/GaN metal-oxide-semiconductor high electron mobility transistor device structure. This model has been developed by incorporating the variation in lowest three energy sub-bands and Fermi level energy in the quantum-well with respect to gate voltage. We noticed that the dependency of lowest sub-band energy with Fermi energy having two fields, which are the lowest sub-band energy is greater and lesser than the Fermi level energy. According to these two fields, we have developed the fermi energy and sheet charge density expressions in each field. By combining each field of the models, developed a unified 2D electron gas sheet charge density model. The Fermi level and sheet charge density are interdependent in the model development. The developed model results are compared with TCAD simulation results and obtain a good consistency between them. This model is fitted to other metal-oxide-semiconductor high electron mobility transistor devices also with modifications in related physical values.

Multisubband transport of the p-type Si₀.₄Ge₀.₆/Ge/Si₀.₄Ge₀.₆ heterostructure has been investigated by means of magnetotransport measurements at low temperatures and high magnetic fields. Two frequency Shubnikov–de Haas oscillations indicate occupation of two subbands. This allows us to determine the densities and mobilities of the charge carriers on each subband. Shubnikov–de Haas oscillations reveal two 2D conduction subbands with carrier effective masses of 0.112m₀ and 0.131m₀. The quantum Hall ferromagnetic states which results from the crossing of two Landau levels with opposite spin and different subband was observed in SiGe systems for the first time.

We present magnetoresistance studies of the quasi-two-dimensional organic conductor $\kappa$-(BETS)$_2$Mn[N(CN)$_2$]$_3$, where BETS stands for bis\-(ethylene\-dithio)\-tetra\-selena\-fulvalene. Under a moderate pressure of 1.4\,kbar, required for stabilizing the metallic ground state, Shubnikov - de Haas oscillations, associated with a classical and a magnetic-breakdown cyclotron orbits on the cylindrical Fermi surface, have been found at fields above 10\,T. The effective cyclotron masses evaluated from the temperature dependence of the oscillation amplitudes reveal strong renormalization due to many-body interactions. The analysis of the relative strength of the oscillations corresponding to the different orbits and its dependence on magnetic field suggests an enhanced role of electron-electron interactions on flat parts of the Fermi surface., Comment: 6 pages, 4 figures

Intrinsic anomalous Nernst effect (ANE), like its Hall counterpart, is generated by Berry curvature of electrons in solids. Little is known about its response to disorder. In contrast, the link between the amplitude of the ordinary Nernst coefficient and the mean-free-path is extensively documented. Here, by studying Co$_3$Sn$_2$S$_2$, a topological half-metallic semimetal hosting sizable and recognizable ordinary and anomalous Nernst responses, we demonstrate an anti-correlation between the amplitude of ANE and carrier mobility. We argue that the observation, paradoxically, establishes the intrinsic origin of the ANE in this system. We conclude that various intrinsic off-diagonal coefficients are set by the way the Berry curvature is averaged on a grid involving the mean-free-path, the Fermi wavelength and the de Broglie thermal length., 10 pages, 9 figures, suppmental materials included

Rapid progress of quantum transport study in topological Dirac semimetal, including observations of quantum Hall effect in two-dimensional (2D) Cd$_{\mathrm{3}}$As$_{\mathrm{2}}$ samples, has uncovered even more interesting quantum transport properties in high-quality and three-dimensional (3D) samples. However, such 3D Cd$_{\mathrm{3}}$As$_{\mathrm{2}}$ films with low carrier density and high electron mobility have been hardly obtained. Here we report the growth and characterization of 3D thick Cd$_{\mathrm{3}}$As$_{\mathrm{2}}$ films adopting molecular beam epitaxy. The highest electron mobility ($\mu$ = 3 $\times$ 10$^{4}$ cm$^{2}$/Vs) among the reported film samples has been achieved at a low carrier density ($\textit{n} = 5$ $\times$ 10$^{16}$ cm$^{-3}$). In the magnetotransport measurement, Hall plateau-like structures are commonly observed in spite of the 3D thick films ($\textit{t} = 120$ nm). On the other hand, field angle dependence of the plateau-like structures and corresponding Shubunikov-de Haas oscillations rather shows a 3D feature, suggesting the appearance of unconventional magnetic orbit, also distinct from the one described by the semiclassical Weyl-orbit equation., Comment: 11 pages, 3 figures + supplementary 6 pages, 3 figures

We present detailed studies of the high-field magnetoresistance of the layered organic metal $\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}\mathrm{Mn}{[\mathrm{N}{(\mathrm{CN})}_{2}]}_{3}$ under a pressure slightly above the insulator-metal transition. The experimental data are analyzed in terms of the Fermi surface properties and compared with the results of first-principles band structure calculations. The calculated size and shape of the in-plane Fermi surface are in very good agreement with those derived from Shubnikov-de Haas oscillations as well as the classical angle-dependent magnetoresistance oscillations. A comparison of the experimentally obtained effective cyclotron masses with the calculated band masses reveals electron correlations significantly dependent on the electron momentum. The momentum- or band-dependent mobility is also reflected in the behavior of the classical magnetoresistance anisotropy in a magnetic field parallel to layers. Other characteristics of the conducting system related to interlayer charge transfer and scattering mechanisms are discussed based on the experimental data. Besides the known high-field effects associated with the Fermi surface geometry, new pronounced features have been found in the angle-dependent magnetoresistance, which might be caused by coupling of the metallic charge transport to a magnetic instability in proximity to the metal-insulator phase boundary.

The results of experimental studies of the Shubnikov-de Haas (SdH) effect in the (013)-HgTe/Hg1-xCdxTe quantum wells (QWs) of electron type of conductivity both with normal and inverted energy spectrum are reported. Comprehensive analysis of the SdH oscillations measured for the different orientations of magnetic field relative to the quantum well plane and crystallographic exes allows us to investigate the anisotropy of the Zeeman effect. For the QWs with inverted spectrum, it has been shown that the ratio of the spin splitting to the orbital one is strongly dependent not only on the orientation of the magnetic field relative to the QW plane but also on the orientation of the in-plane magnetic field component relative to crystallographic axes laying in the QW plane that implies the strong anisotropy of in-plane g-factor. In the QW with normal spectrum, this ratio strongly depends on the angle between the magnetic field and the normal to the QW plane and reveals a very slight anisotropy in the QW plane. To interpret the data, the Landau levels in the tilted magnetic field are calculated within the framework of four-band kP model. It is shown that the experimental results can be quantitatively described only with taking into account the interface inversion asymmetry. © 2020 American Physical Society. We are grateful to E. L. Ivchneko for useful discussions. The work has been supported in part by the Russian Foundation for Basic Research (Grant No. 18-02-00050), by Act 211 Government of the Russian Federation, Agreement No. 02.A03.21.0006, by the Ministry of Science and Higher Education of the Russian Federation under Project No. FEUZ-2020-0054, and by the FASO of Russia (theme “Electron” No. 01201463326).

We present detailed studies of the high-field magnetoresistance of the layered organic metal κ-(BETS)2Mn- [N(CN)2]3 under a pressure slightly above the insulator-metal transition. The experimental data are analyzed in terms of the Fermi surface properties and compared with the results of first-principles band structure calculations. The calculated size and shape of the in-plane Fermi surface are in very good agreement with those derived from Shubnikov-de Haas oscillations as well as the classical angle-dependent magnetoresistance oscillations. A comparison of the experimentally obtained effective cyclotron masses with the calculated band masses reveals electron correlations significantly dependent on the electron momentum. The momentum- or band-dependent mobility is also reflected in the behavior of the classical magnetoresistance anisotropy in a magnetic field parallel to layers. Other characteristics of the conducting system related to interlayer charge transfer and scattering mechanisms are discussed based on the experimental data. Besides the known high-field effects associated with the Fermi surface geometry, new pronounced features have been found in the angle-dependent magnetoresistance, which might be caused by coupling of the metallic charge transport to a magnetic instability in proximity to the metal-insulator phase boundary., We are grateful to N.D. Kushch for providing the high-quality crystals for our studies and to P.D. Grigoriev for numerous useful discussions. The work was supported by the German Research Foundation (DFG) via the Grant No. KA 1652/4-1. The high-field measurements were done under support of the LNCMI-CNRS, member of the European Magnetic Field Laboratory (EMFL). V.N.Z. acknowledges the support from RFBR Grant No. 18-02-00280. Work in Spain was supported by the Spanish Ministerio de Economa y Competitividad (Grants No. FIS2015-64886-C5-4-P and No. CTQ2015-64579-C3-3-P) and Generalitat de Catalunya (2017SGR1506, 2017SGR1289, and XRQTC). E.C. acknowledges support from the Severo Ochoa Centers of Excellence Program under Grant No. SEV-2015-0496. P.A. acknowledges support from the Maria de Maeztu Units of Excellence Program under Grant No. MDM-2017-0767.

In this paper, we show how the ultracold atom analogue of the two-dimensional de Haas-van Alphen effect in electronic condensed matter systems can be induced by optical fields in a neutral atomic system. The interaction between the suitable spatially varying laser fields and tripod-type trapped atoms generates a synthetic magnetic field which leads the particles to organize themselves in Landau levels. Initially, with the atomic gas in a regime of lowest Landau level, we display the oscillatory behaviour of the atomic energy and its derivative with respect to the effective magnetic field (B) as a function of 1 B . Furthermore, we estimate the area of the Fermi circle of the two-dimensional atomic gas.

Features in the transverse magnetoresistance of single-crystalline diluted magnetic semiconductors of a (Cd1&ndash, x&ndash, yZnxMny)3As2 system with x + y = 0.3 have been found and analyzed in detail. Two groups of samples have been examined. The samples of the first group were thermally annealed for a long time, whereas the samples of the second group were not thermally annealed. The Shubnikov&ndash, de Haas (SdH) oscillations were observed for both groups of the samples within a 4.2 &divide, 30 K temperature range and under transverse magnetic field sweeping from 0 up to 11 T. The value of a phase shift, according to the SdH oscillations, was found to be a characteristic of the Berry phase existing in all the samples, except the unannealed sample with y = 0.08. Thickness of 2D surface topological nanolayers for all the samples was estimated. The thickness substantially depended on Mn concentration. The experimental dependence of reduced cyclotron mass on the Fermi wave vector, extracted from the SdH oscillations for the samples with different doping levels, is in satisfactory agreement with the predicted theoretical linear dependence. The existence of the Dirac fermions in all the samples studied (except the unannealed sample with y = 0.08) can be concluded from this result.

Charge carriers parameters on a 2D-layer surface for (Cd1−x−yZnxMny)3As2 (y = 0.08) (the concentration n 2 D = 1.9 × 1012 cm–2, the effective value of the 2D-layer d 2 D = n 2 D / n 3 D = 14.5 nm, the wave vector k F = 0.1 nm–1, the charge carriers relaxation time due to dispersion τ D = 1.8 × 10–13 s, the velocity of charge carriers on Fermi surface v F = ℏ k F / m c = 2.65 × 105 m s−1, the mean free path l F = v F τ D = 47.7 nm) were determined. It was found that the dependence of the cyclotron mass m с (0)/m0 on Fermi wave vector k F for (Cd1−x−yZnxMny)3As2 (y = 0.08) is in compliance with a theoretical linear dependence, that describes mass-less Dirac fermions.

We report on beating appearance in Shubnikov-de Haas oscillations in conduction band of 18-22nm HgTe quantum wells under applied top-gate voltage. Analysis of the beatings reveals two electron concentrations at the Fermi level arising due to Rashba-like spin splitting of the first conduction subband H1. The difference dN_s in two concentrations as a function of the gate voltage is qualitatively explained by a proposed toy electrostatic model involving the surface states localized at quantum well interfaces. Experimental values of dN_s are also in a good quantitative agreement with self-consistent calculations of Poisson and Schrodinger equations with eight-band kp Hamiltonian. Our results clearly demonstrate that the large spin splitting of the first conduction subband is caused by surface nature of $H1$ states hybridized with the heavy-hole band., 7 pages, 7 figures

We report a study of quantum oscillations in the high-field magneto-resistance of the nodal-line semimetal HfSiS. In the presence of a magnetic field up to 31 T parallel to the c-axis, we observe quantum oscillations originating both from orbits of individual electron and hole pockets, and from magnetic breakdown between these pockets. In particular, we find an oscillation associated with a breakdown orbit enclosing one electron and one hole pocket in the form of a `figure of eight'. This observation represents an experimental confirmation of the momentum space analog of Klein tunneling. When the c-axis and the magnetic field are misaligned with respect to one another, this oscillation rapidly decreases in intensity. Finally, we extract the cyclotron masses from the temperature dependence of the oscillations, and find that the mass of the 'figure of eight' orbit corresponds to the sum of the individual pockets, consistent with theoretical predictions for Klein tunneling in topological semimetals., 6 pages, 4 figures

Monobismuthides of yttrium and lutetium are shown as new representatives of materials which exhibit extreme magnetoresistance and magnetic-field-induced resistivity plateau. At low temperatures and in magnetic field of 9T the magnetoresistance attains the order of magnitude of 10,000% and 1,000%, on YBi and LuBi, respectively. Our thorough examination of electron transport properties of both compounds show that observed features are the consequence of nearly perfect carrier compensation rather than of possible nontrivial topology of electronic states. The field-induced plateau of electrical resistivity can be explained with Kohler scaling. Anisotropic multi-band model of electronic transport describes very well the magnetic field dependence of electrical resistivity and Hall resistivity. Data obtained from the Shubnikov-de Haas oscillations analysis also confirm that Fermi surface of each compound contains almost equal amounts of holes and electrons. First-principle calculations of electronic band structure are in a very good agreement with the experimental data., Comment: 9 pages, 9 figures, 3 tables (+3 pages, 2 figures and 1 table in Supplemental Material)

Renormalization of Landau level energies in graphene in strong magnetic field due to Coulomb interaction is studied theoretically, and calculations are compared with two experiments on carrier-density dependent scanning tunneling spectroscopy. An approximate preservation of the square-root dependence of the energies of Landau levels on their numbers and magnetic field in the presence of the interaction is examined. Many-body calculations of the renormalized Fermi velocity with the statically screened interaction taken in the random-phase approximation show good agreement with both experiments. The crucial role of the screening in achieving quantitative agreement is found. The main contribution to the observed rapid logarithmic growth of the renormalized Fermi velocity on approach to the charge neutrality point turned out to be caused not by mere exchange interaction effects, but by weakening of the screening at decreasing carrier density. The importance of a self-consistent treatment of the screening is also demonstrated., 8 pages, 6 figures, 2 tables; results of self-consistent iterative calculations were included

Quantum oscillations of response functions in high magnetic fields tend to reveal some of the most interesting properties of metals. In particular, the oscillation phase shift is sensitive to topological band features, thereby helping to identify the presence of Weyl fermions. In this work we predict characteristic parameter dependence of the phase shift for Weyl fermions with tilted and overtilted dispersion (type I and type II Weyl fermions) and an arbitrary topological charge (multi-Weyl fermions). For type-II Weyl fermions our calculations capture the case of magnetic breakthrough between the electron and the hole part of the dispersion. Here the phase shift turns out to depend only on the quantized topological charge due to cancellation of non-universal contributions from the electron and the hole part., 5 pages, 3 figures, Supplemental Material

Electrical properties of N-polar undoped and Mg-doped InN layers and In-polar undoped InN layers grown by plasma-assisted molecular beam epitaxy (PA MBE) were studied. Transport parameters of the surface and interface layers were determined from the measurements of the Hall coefficient and resistivity as well as the Shubnikov-de Haas oscillations at magnetic fields up to 60 T. Contributions of the 2D surface, 3D near-interface, and 2D interface layers to the total conductivity of the InN films were defined and discussed to be dependent on InN surface polarity, Mg doping, and PA MBE growth conditions.

The quantum Langevin formalism is used to study the charge carrier transport in a two-dimensional sample. The center of mass of charge carriers is visualized as a quantum particle, while an environment acts as a heat bath coupled to it through the particle–phonon interaction. The dynamics of the charge carriers is limited by the average collision time which takes effectively into account the two-body effects. The functional dependencies of particle–phonon interaction and average collision time on the temperature and magnetic field are phenomenologically treated. The galvano-magnetic and thermo-magnetic effects in the quantum system appear as the results of the transitional processes at low temperatures.

The electronic structures of a representative rare earth monopnictide (i.e., DySb) under high magnetic field (i.e., in the ferromagnetic state) are studied from both experimental and theoretical aspects. A non-saturated extremely large positive magnetoresistance (XMR) is observed (as large as 3.7 × 104% at 1.8 K and 38.7 T), along with the Shubnikov-de Haas oscillations that are well reproduced by our first principles calculations. Three possible origins of XMR are examined. Although a band inversion is found theoretically, suggesting that DySb might be topologically nontrivial, it is deeply underneath the Fermi level, which rules out a topological nature of the XMR. The total densities of electron-like and hole-like carriers are not fully compensated, showing that compensation is unlikely to account for the XMR. The XMR is eventually understood in terms of high mobility that is associated with the steep linear bands. This discovery is important to the intensive studies on the XMR of rare earth monopnictides.The electronic structures of a representative rare earth monopnictide (i.e., DySb) under high magnetic field (i.e., in the ferromagnetic state) are studied from both experimental and theoretical aspects. A non-saturated extremely large positive magnetoresistance (XMR) is observed (as large as 3.7 × 104% at 1.8 K and 38.7 T), along with the Shubnikov-de Haas oscillations that are well reproduced by our first principles calculations. Three possible origins of XMR are examined. Although a band inversion is found theoretically, suggesting that DySb might be topologically nontrivial, it is deeply underneath the Fermi level, which rules out a topological nature of the XMR. The total densities of electron-like and hole-like carriers are not fully compensated, showing that compensation is unlikely to account for the XMR. The XMR is eventually understood in terms of high mobility that is associated with the steep linear bands. This discovery is important to the intensive studies on the XMR of rare earth monopnictides.