De Haas-van Alphen Research Articles

De Haas–van Alphen Effect in Pressure-Induced Superconductor CrAs

We report on the first observation of the de Haas–van Alphen (dHvA) effect in CrAs under hydrostatic pressures of up to 2.2 GPa, exceeding the critical pressure Pc ∼ 0.7 GPa, where the antiferromag...

Quasi-two-dimensional relativistic fermions probed by de Haas–van Alphen quantum oscillations in LuSn2

We report de Haas--van Alphen (dHvA) quantum oscillation studies on a layered compound $\mathrm{Lu}{\mathrm{Sn}}_{2}$. Through the analyses of the dHvA oscillation data, we find this material has several 3D bands and one quasi-2D band hosting relativistic fermions. Compared to previously reported dHvA oscitations in $\mathrm{Y}{\mathrm{Sn}}_{2,}$, the oscillation component arising from the quasi-2D band is significantly enhanced. From structural analyses using single-crystal x-ray diffraction, we find the distorted Sn-square net layer is less corrugated than $\mathrm{Y}{\mathrm{Sn}}_{2,}$, which accounts for the enhancement of two dimensionality of the relativistic fermions created in this layer. This result suggests that the dimensionality of relativistic band in $\mathrm{RE}{\mathrm{Sn}}_{2}$ ($\mathrm{RE}=\mathrm{rare}$ earth) can be tuned by electronegativity of RE. Moreover, we also find the 3D relativistic bands are pushed closer to the Fermi level with respect to $\mathrm{Y}{\mathrm{Sn}}_{2,}$ due to enhanced spin-orbital coupling. These findings imply $\mathrm{RE}{\mathrm{Sn}}_{2}$ can be an interesting platform for seeking new topological states via the tuning of electronegativity, spin-orbital coupling, and magnetism.

Inelastic particle scattering by rotating harmonically trapped quantum gases

In this article, we focus on describing the inelastic particle scattering by quantum scatterers in a rotating harmonic trap with the presence of delta potential. We have obtained an inelastic differential scattering cross-section which depends on temperature and rotational speed. We have shown the possibility of observing effects of the artificial the de Haas-van Alphen (dHvAE)-like oscillation by inelastic particle scattering approaches for rotating Fermi scatterers which are closely connected to magnetization in solid-state physics. We discuss the weak inter-scatterer interaction effect on differential scattering cross-sections for rotating Bose gases. We also have obtained temperature dependency on scattering cross-sections for non-rotating harmonic trap. The idea of probing degenerate quantum gases with matter waves through scattering or quenching has recently attracted a lot of attention and is clearly going to be important in the future.

Three-dimensional topological semimetal phase in layered TaNiTe5 probed by quantum oscillations

Layered three-dimensional (3D) topological semimetals have attracted intensively attention due to the exotic phenomena and abundantly tunable properties. Here we report the experimental evidence for the 3D topological semimetal phase in layered material TaNiTe5 single crystals through quantum oscillations. Strong quantum oscillations have been observed with diamagnetism background in TaNiTe5. By analyzing the de Haas-van Alphen oscillations, multi-periodic oscillations were extracted, in content with magnetotransport measurements. Moreover, nontrivial "{\pi}" Berry phase with 3D Fermi surface is identified, indicating the topologically nontrivial feature in TaNiTe5. Additionally, we demonstrated the thin-layer of TaNiTe5 crystals is highly feasible by the mechanical exfoliation, which offers a platform to explore exotic properties in low dimensional topological semimetal and paves the way for potential applications in nanodevices.

Robust Fermi-Surface Morphology of CeRhIn_{5} across the Putative Field-Induced Quantum Critical Point.

We report a comprehensive de Haas-van Alphen (dHvA) study of the heavy-fermion material CeRhIn_{5} in magnetic fields up to 70T. Several dHvA frequencies gradually emerge at high fields as a result of magnetic breakdown. Among them is the thermodynamically important β_{1} branch, which has not been observed so far. Comparison of our angle-dependent dHvA spectra with those of the non-4f compound LaRhIn_{5} and with band-structure calculations evidences that the Ce 4f electrons in CeRhIn_{5} remain localized over the whole field range. This rules out any significant Fermi-surface reconstruction, either at the suggested nematic phase transition at B^{*}≈30 T or at the putative quantum critical point at B_{c}≃50 T. Our results rather demonstrate the robustness of the Fermi surface and the localized nature of the 4f electrons inside and outside of the antiferromagnetic phase.

Description of the Magnetization Oscillations of a Silicon Nanostructure in Weak Fields at Room Temperature. The Lifshitz–Kosevich Formula with Variable Effective Carrier Mass

A formalism of the statistical approach to describing de Haas–van Alphen oscillations known as the Lifshitz–Kosevich formula is developed as applied to a low-dimensional system with an effective carrier mass depending on an external magnetic field. The statistical approach makes it possible to perform more detailed interpretation of the experimental results and analyze the interrelation of the dependence found by us of the effective carrier mass with the individual features of the structure of a silicon nanosandwich caused by the formation of negative-U δ barriers in its composition.

Anisotropic superconductivity and quantum oscillations in the layered dichalcogenide TaSnS2

${\mathrm{TaSnS}}_{2}$ single crystal and polycrystalline samples are investigated in detail by magnetization, electrical resistivity, and specific heat as well as Raman spectroscopy and nuclear magnetic resonance (NMR). Studies are focused on the temperature and magnetic field dependence of the superconducting state. We determine the critical fields for both directions $B\ensuremath{\parallel}c$ and $B\ensuremath{\perp}\phantom{\rule{0.16em}{0ex}}c$. Additionally, we investigate the dependence of the resistivity, the critical temperature, and the structure through Raman spectroscopy under high pressure up to 10 GPa. At a pressure of $\ensuremath{\approx}3\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$ the superconductivity is suppressed below our minimum temperature. The Sn NMR powder spectrum shows a single line which is expected for the ${\mathrm{TaSnS}}_{2}$ phase and confirms the high sample quality. Pronounced de Haas-van Alphen oscillations in the ac susceptibility of polycrystalline sample reveal two pairs of frequencies indicating coexisting small and large Fermi surfaces. The effective mass of the smaller Fermi surface is $\ensuremath{\approx}0.5{m}_{\mathrm{e}}$. We compare these results with the band structures from DFT calculations. Our findings on ${\mathrm{TaSnS}}_{2}$ are discussed in terms of a quasi-two-dimensional BCS superconductivity.

Modulation of Landau levels and de Haas-van Alphen oscillation in magnetized graphene by uniaxial tensile strain/ stress

The strain engineering technique allows us to alter the electronic properties of graphene in various ways. Within the continuum approximation, the influences of strain result in the appearance of a pseudo-gauge field and modulated Fermi velocity. In this study, we investigate theoretically the effect of linear uniaxial tensile strain and/or stress, which makes the Fermi velocity anisotropic, on a magnetized graphene sheet in the presence of an applied electrostatic voltage. More specifically, we analyze the consequences of the anisotropic nature of the Fermi velocity on the structure Landau levels and de Haas-van Alphen (dHvA) quantum oscillation in the magnetized graphene sheet. The effect of the direction of the applied strain has also been discussed.

Quantum oscillations with angular dependence in PdTe2 single crystals

The layered transition-metal dichalcogenide PdTe2 has been discovered to possess bulk Dirac points as well as topological surface states. By measuring the magnetization (up to 7 T) and magnetic torque (up to 35 T) in single crystalline PdTe2, we observe distinct de Haas–van Alphen (dHvA) oscillations. Eight frequencies are identified with H||c, with two low frequencies (F α = 8 T and F β = 117 T) dominating the spectrum. The effective masses obtained by fitting the Lifshitz–Kosevich (LK) equation to the data are and where m 0 is the free electron mass. The corresponding Landau fan diagrams allow the determination of the Berry phase for these oscillations resulting in values of ∼0.67π for the 3D α band (hole-type) (down to the 1st Landau level) and ∼0.23π–0.73π for the 3D β band (electron-type) (down to the 3rd Landau level). By investigating the angular dependence of the dHvA oscillations, we find that the frequencies and the corresponding Berry phase (ΦB) vary with the field direction, with a ΦB ∼ 0 when H is 10°–30° away from the ab plane for both α and β bands. The multiple band nature of PdTe2 is further confirmed from Hall effect measurements.

Large magnetoresistance and nonzero Berry phase in the nodal-line semimetal MoO2

We performed calculations of the electronic band structure and the Fermi surface as well as measured the longitudinal resistivity rhoxx(T,H), Hall resistivity rhoxy(T,H) and quantum oscillations of the magnetization as a function of temperature at various magnetic fields for MoO2 with monoclinic crystal structure. The band structure calculations show that MoO2 is a nodal-line semimetal when spin-orbit coupling is ignored. It was found that a large magnetoresistance reaching 5.03x10^4% at 2 K and 9 T, its nearly quadratic field dependence and a field-induced up-turn behavior of rhoxx(T), the characteristics common for many topologically non-trivial as well as trivial semimetals, emerge also in MoO2. The observed properties are attributed to a perfect charge-carrier compensation, evidenced by both calculations relying on the Fermi surface topology and the Hall resistivity measurements. Both the observation of negative magnetoresistance for magnetic field along the current direction and the non-zero Berry phase in de Haas-van Alphen measurements indicate that pairs of Weyl points appear in MoO2, which may be due to the crystal symmetry breaking. These results highlight MoO2 as a new platform materials for studying the topological properties of oxides.

Electron transport in Dirac nodal-line semimetal ZrSiS

We report a study of magnetization and transport properties such as electrical resistivity, thermal conductivity, and thermal Hall conductivity in high fields and at low temperatures for ZrSiS single crystals. Here, we find that the thermal conductivity (κxx/T) is strongly suppressed in applied fields, having a good correlation with the large positive transverse magnetoresistance (TMR). The thermal Hall conductivity (κxy/T) displays a sharp peak at extremely low field which reveals the high mobility of the electrons. In addition, the TMR displays clear Shubnikov de Haas (SdH) oscillation at low temperatures. Although the Zeeman splitting is obviously appeared in de Haas-van Alphen (dHvA) oscillation of the magnetization measurements and distinguished easily from the SdH oscillation. Negative longitudinal magnetoresistance (LMR) is also observed in ZrSiS which may be related to the chiral anomaly.

Intrinsic Bulk Quantum Oscillations in a Bulk Unconventional Insulator SmB6.

SummaryThe finding of bulk quantum oscillations in the Kondo insulator SmB6 proved a considerable surprise. Subsequent measurements of bulk quantum oscillations in other correlated insulators including YbB12 lent support to our discovery of a class of bulk unconventional insulators that host bulk quantum oscillations. Here we perform a series of experiments to examine evidence for the intrinsic character of bulk quantum oscillations in floating zone-grown single crystals of SmB6 that have been the subject of our quantum oscillation studies. We present results of thermodynamic, transport, and composition analysis experiments on pristine floating zone-grown single crystals of SmB6 and compare quantum oscillations with metallic LaB6 and elemental aluminum. These results establish the intrinsic origin of quantum oscillations from the insulating bulk of floating zone-grown SmB6. The similarity of the Fermi surface in insulating SmB6 with the conduction-electron Fermi surface in metallic hexaborides is at the heart of a theoretical mystery.

Quantum Oscillations and Electronic Structure in the Large-Chern-Number Topological Chiral Semimetal PtGa*Supported by the National Key Research and Development Program of China (Grant Nos. 2019YFA0308602, 2018YFA0305700 and 2016YFA0300600), the National Natural Science Foundation of China (Grant Nos. 11874422 and 11574391), the Fundamental Research Funds for the Central Universities, and the Research Funds of Renmin University of China (Grant Nos. 19XNLG18

We report the magnetoresistance (MR), de Haas-van Alphen (dHvA) oscillations and the electronic structures of single-crystal PtGa. The large unsaturated MR is observed with the magnetic field B ∥ [111]. Evident dHvA oscillations with the B ∥ [001] configuration are observed, from which twelve fundamental frequencies are extracted and the spin-orbit coupling (SOC) induced band splitting is revealed. The light cyclotron effective masses are extracted from the fitting by the thermal damping term of the Lifshitz–Kosevich formula. Combining with the calculated frequencies from the first-principles calculations, the dHvA frequencies F1/F3 and F11/F12 are confirmed to originate from the electron pockets at Γ and R, respectively. The first-principles calculations also reveal the existence of spin-3/2 Rarita–Schwinger–Weyl fermions and time-reversal doubling of the spin-1 excitation at Γ and R with large Chern numbers of ± 4 when SOC is included.

Extremely large magnetoresistance, anisotropic Hall effect, and Fermi surface topology in single-crystalline WSi2

We report on the observation of a nonsaturating, extremely large magnetoresistance (XMR) and the Fermi surface topology of a high quality $\mathrm{W}{\mathrm{Si}}_{2}$ single crystal grown by the Czochralski method. The magnetoresistance at $T=2\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ reaches a value $\ensuremath{\approx}{10}^{5}%$ in 14 T magnetic field with no sign of saturation. The Hall resistivity data of $\mathrm{W}{\mathrm{Si}}_{2}$ was found to be highly anisotropic. The analysis of magnetoconductivity data of $\mathrm{W}{\mathrm{Si}}_{2}$ revealed a near compensation of charge carrier with relatively low carrier density as compared to that of a normal metal. The observed anisotropic Hall resistivity in $\mathrm{W}{\mathrm{Si}}_{2}$ is due to the presence of multiple bands and Fermi pockets responsible for the transport phenomena in it. The extremely large carrier mobility and near compensation of charge carriers are responsible for the nonsaturating XMR behavior in $\mathrm{W}{\mathrm{Si}}_{2}$ crystal. The band structure calculation and de Haas-van Alphen effect measurement depict a cylindrical Fermi surface from which the associated quantum parameters have been obtained. The magnetotransport data of $\mathrm{W}{\mathrm{Si}}_{2}$ along both the crystallographic directions follows the universal temperature-field triangular phase diagram as observed in other materials exhibiting XMR behavior.

Linear and quadratic magnetoresistance in the semimetal SiP2

Multiple mechanisms for extremely large magnetoresistance (XMR) found in many topologically nontrivial/trivial semimetals have been theoretically proposed, but experimentally it is unclear which mechanism is responsible in a particular sample. In this article, by the combination of band structure calculations, numerical simulations of magnetoresistance (MR), Hall resistivity and de Haas-van Alphen (dHvA) oscillation measurements, we studied the MR anisotropy of SiP$_{2}$ which is verified to be a topologically trivial, incomplete compensation semimetal. It was found that as magnetic field, $H$, is applied along the $a$ axis, the MR exhibits an unsaturated nearly linear $H$ dependence, which was argued to arise from incomplete carriers compensation. For the $H$ $\parallel$ [101] orientation, an unsaturated nearly quadratic $H$ dependence of MR up to 5.88 $\times$ 10$^{4}$$\%$ (at 1.8 K, 31.2 T) and field-induced up-turn behavior in resistivity were observed, which was suggested due to the existence of hole open orbits extending along the $k_{x}$ direction. Good agreement of the experimental results with the simulations based on the calculated Fermi surface (FS) indicates that the topology of FS plays an important role in its MR.

Multiple Dirac nodes and symmetry protected Dirac nodal line in orthorhombic α -RhSi

Owing to their chiral cubic structure, exotic multifold topological excitations have been predicted and recently observed in transition metal silicides like $\beta$-RhSi. Herein, we report that the topological character of RhSi is also observed in its orthorhombic $\alpha$-phase which displays multiple types of Dirac nodes very close to the Fermi level ($\varepsilon_F$) with the near absence of topologically trivial carriers. We discuss the symmetry analysis, band connectivity along high-symmetry lines using group representations, the band structure, and the nature of the Dirac points and nodal lines occurring near $\varepsilon_F$. The de Haas-van Alphen effect (dHvA) indicates a Fermi surface in agreement with the calculations. We find an elliptically-shaped nodal line very close to $\varepsilon_F$ around and near the $S$-point on the $k_y-k_z$ plane that results from the intersection of two upside-down Dirac cones. The two Dirac points of the participating Kramers degenerate bands are only 5 meV apart, hence an accessible magnetic field might induce a crossing between the spin-up partner of the upper-Dirac cone and the spin-down partner of the lower Dirac cone, possibly explaining the anomalies observed in the magnetic torque.

Orbital crossing in spin-split Fermi surfaces and anisotropic effective mass of the noncentrosymmetric heavy-fermion paramagnet UPt5

We report the single-crystal growth of the noncentrosymmetric cubic heavy-fermion paramagnet ${\mathrm{UPt}}_{5}$ and comparative Fermi surface studies of de Haas-van Alphen (dHvA) experiments and theoretical band calculations. We also present the results of single-crystal x-ray diffraction, electrical resistivity, heat capacity, and magnetization measurements using single crystals of ${\mathrm{UPt}}_{5}$. The dHvA experiments reveal nearly spherical split hole Fermi surfaces and largely split electron Fermi surfaces, which are in agreement with the results of a band-structure calculation. The largely split electron Fermi surfaces may be understood through the antisymmetric spin-orbit interaction derived from U-$5f$ and Pt-$5d$ electrons. We explain the observed unexpected dHvA frequencies quasiquantitatively based on orbital crossing using the coupled network analysis in the split hole Fermi surface pair. Furthermore, the temperature dependence of the dHvA amplitude reveals enhanced cyclotron effective masses of up to $29{m}_{0}$ and a peculiar anisotropic effective mass in the paramagnetic cubic heavy-fermion ${\mathrm{UPt}}_{5}$.

Bulk Fermi surfaces of the Dirac type-II semimetallic candidate NiTe2

Here, we present a study on the Fermi-surface of the Dirac type-II semi-metallic candidate NiTe$_2$ via the temperature and angular dependence of the de Haas-van Alphen (dHvA) effect measured in single-crystals grown through Te flux. In contrast to its isostructural compounds like PtSe$_2$, band structure calculations predict NiTe$_2$ to display a tilted Dirac node very close to its Fermi level that is located along the $\Gamma$ to A high symmetry direction within its first Brillouin zone (FBZ). The angular dependence of the dHvA frequencies is found to be in agreement with the first-principle calculations when the electronic bands are slightly shifted with respect to the Fermi level ($\varepsilon_F$), and therefore provide support for the existence of a Dirac type-II node in NiTe$_2$. Nevertheless, we observed mild disagreements between experimental observations and density Functional theory calculations as, for example, nearly isotropic and light experimental effective masses. This indicates that the dispersion of the bands is not well captured by DFT. Despite the coexistence of Dirac-like fermions with topologically trivial carriers, samples of the highest quality display an anomalous and large, either linear or sub-linear magnetoresistivity. This suggests that Lorentz invariance breaking Dirac-like quasiparticles dominate the carrier transport in this compound.

Thermal and magnetic properties of landau quantized group VI dichalcogenide carriers in the approach to the degenerate limit

This work is concerned with determination of the thermal and magnetic behavior of the Group VI Dichalcogenides in a quantizing magnetic field. Our discussion includes analysis of the Grand Potential, Helmholtz Free Energy, partition functions (grand and ordinary) and the entropy and specific heat: their dependencies on temperature and magnetic field strength are carefully examined, particularly in the degenerate regime and the approach to zero temperature. The joint dependence on magnetic field and temperature is also determined for the Dichalcogenide magnetic moment in the degenerate statistical regime, replete with de Haas–van Alphen (dHvA) oscillatory phenomenology and also above the zero–temperature limit.

Topological Dirac states in a layered telluride TaPdTe5 with quasi-one-dimensional PdTe2 chains

We report the synthesis and systematic studies of a new layered ternary telluride TaPdTe5 with quasi-one-dimensional PdTe2 chains. This compound crystalizes in a layered orthorhombic structure with space group Cmcm. Analysis of its curved field-dependent Hall resistivity, using the two-band model, indicates the hole-dominated transport with a high mobility ${\mu}_h$ = 2.38 $\times$ 10$^3$ cm$^2$ V$^{-1}$ s$^{-1}$ at low temperatures. The in-plane magnetoresistance (MR) displays significant anisotropy with field applied along the crystallographic $b$ axis. The MR with the current applied along the $c$-axis is also measured in high magnetic fields up to 51.7 T. Remarkably, it follows a power-law dependence and reaches (9.5 $\times$ 10$^3$)% at 2.1 K without any signature of saturation. The De Haas-van Alphen oscillations show a small Fermi-surface pocket with a nontrivial Berry phase. The Shubnikov-de Haas (SdH) oscillations are detected at low temperatures and under magnetic fields above 28.5 T. Two effective masses $m^*$ (0.26$m_e$ and 0.41$m_e$) are extracted from the oscillatory SdH data. Our first-principles calculations unveil a topological Dirac cone in its surface states, and, in particular, the topological index indicates that TaPdTe$_5$ is a topologically nontrivial material.