De Haas-van Alphen Research Articles

Fermi surface and light quasi particles in hourglass nodal chain metal β-ReO2

Quantum oscillations (QOs) in magnetic torque and electrical resistivity were measured to investigate the electronic structure of β-ReO2, a candidate hourglass nodal chain (NC) metal (Dirac loop chain metal). All the de Haas–van Alphen oscillation branches measured at 30 mK in magnetic fields of up to 17.5 T were consistent with first-principles calculations predicting four Fermi surfaces (FSs). The small-electron FS of the four FSs exhibited a very small cyclotron mass, 0.059 times that of the free electrons, which is likely related to the linear dispersion of the energy band. The consistency between the QO results and band calculations indicates the presence of the hourglass NC predicted for β-ReO2 in the vicinity of the Fermi energy.

In-plane Fermi surface mapping of ZrSiS and HfSiS by de Haas-van Alphen oscillations

We have conducted a comprehensive experimental investigation of the in-plane de Haas van Alphen quantum oscillations in ZrSiS and HfSiS and compared the results to the ab-initio calculations. We found a moderately good agreement for a set of frequencies located between 100 T and 200 T. These could be associated with extremal orbitals of the electron pockets located around the k_z=\pm\pi/2ckz=±π/2c planes at the edge of the 1st Brillouin zone. In contrast, the experimentally detected low-frequency set of oscillations found around 20 T could not be reproduced by the calculations. Further refinement of the ab-initio calculation has to be conducted to fully capture all the observed features of the Fermi surface in ZrSiS and HfSiS.

Self-consistent thermodynamic potential for magnetized QCD matter

Within the two-flavor Nambu--Jona-Lasinio model, we derive a self-consistent thermodynamic potential $\Omega$ for a QCD matter in an external magnetic field $B$. To be consistent with Schwinger's renormalization spirit, counter terms with vacuum quark mass are introduced into $\Omega$ and then the explicit $B$-dependent parts can be regularized in a cutoff-free way. Following that, explicit expressions of gap equation and magnetization can be consistently obtained according to the standard thermodynamic relations. The formalism is able to reproduce the paramagnetic feature of a QCD matter without ambiguity. For more realistic study, a running coupling constant is also adopted to account for the inverse magnetic catalysis effect. It turns out that the running coupling would greatly suppress magnetization at large $B$ and is important to reproduce the temperature enhancement effect to magnetization. The case with finite baryon chemical potential is also explored: no sign of first-order transition is found by varying $B$ for the running coupling and the de Haas-van Alphen oscillation shows up in the small $B$ region.

Effect of minimal length on Landau diamagnetism and de Haas–van Alphen effect

We study Landau diamagnetism in the framework of generalised uncertainty principle(GUP). We calculate the correction to magnetisation and susceptibility by constructing the grand partition function of diamagnetic material in this framework. We explicitly show that Curie’s law gets a temperature-independent correction which vanishes when quantum gravity effects are neglected. We further consider the low-temperature limit to find how GUP affects the de Haas–van Alphen effect.

Evidence for unconventional superconductivity and nontrivial topology in PdTe

PdTe is a superconductor with Tc ~ 4.25 K. Recently, evidence for bulk-nodal and surface-nodeless gap features has been reported in PdTe. Here, we investigate the physical properties of PdTe in both the normal and superconducting states via specific heat and magnetic torque measurements and first-principles calculations. Below Tc, the electronic specific heat initially decreases in T3 behavior (1.5 K < T < Tc) then exponentially decays. Using the two-band model, the superconducting specific heat can be well described with two energy gaps: one is 0.372 meV and another 1.93 meV. The calculated bulk band structure consists of two electron bands (α and β) and two hole bands (γ and η) at the Fermi level. Experimental detection of the de Haas-van Alphen (dHvA) oscillations allows us to identify four frequencies (Fα = 65 T, Fβ = 658 T, Fγ = 1154 T, and Fη = 1867 T for H // a), consistent with theoretical predictions. Nontrivial α and β bands are further identified via both calculations and the angle dependence of the dHvA oscillations. Our results suggest that PdTe is a candidate for unconventional superconductivity.

Artificial magnetism for a harmonically trapped Fermi gas in a synthetic magnetic field

We have analytically explored the artificial magnetism for a 3D spin-polarized harmonically trapped ideal Fermi gas of electrically neutral particles exposed to a uniform synthetic magnetic field. Though polarization of the spin is necessary for trapping electrically neutral atoms in a magneto-optical trap, Pauli paramagnetism can not be studied for the spin-polarized Fermi system. However, it is possible to study Landau diamagnetism and de Haas-van Alphen effect for such a system. We have unified the artificial Landau diamagnetism and the artificial de Haas-van Alphen effect in a single framework for all temperatures as well as for all possible magnitudes of the synthetic magnetic field in the thermodynamic limit. Our prediction is testable in the present-day experimental setup for ultracold fermionic atoms in magneto-optical trap.

Localization of electrons in the field of impurity atoms on the surface of a nanotube

The localization of electrons in the field of isolated nonmagnetic impurity atoms on the surface of a nanotube is considered. A model of a Gaussian separable impurity potential capable of localizing an electron at any intensity is used. The positions of the local level are found. The positions of the resonances are found, their widths are estimated. It is shown that the positions of the resonances experience oscillations similar to the de Haas–van Alphen oscillations, when changing the radius of the tube.

De Haas van Alphen oscillations in hybridization-gap insulators as a sudden change in the diamagnetic moment of Landau levels

This note revisits the semiclassical theory of quantum oscillations in hybridization-gap insulators, and shows that the physical origin of the oscillations, at T = 0 K, is a sudden change in the diamagnetic moment of each Landau level as it crosses the hybridized region of the valence band.

Magnetized neutron star crust within effective relativistic mean-field model

Even though the crystallize nature of the neutron star crust plays a pivotal role in describing various fascinating astrophysical observations, its microscopic structure is not fully understood in the presence of a colossal magnetic field. In the present work, we study the crustal properties of a neutron star within an effective relativistic mean field framework in the presence of magnetic field strength $\sim 10^{17}$G. We calculate the equilibrium composition of the outer crust by minimizing the Gibbs free energy using the most recent atomic mass evaluations. The magnetic field significantly affects the equation of state (EoS) and the properties of the outer crust, such as neutron drip density, pressure, and melting temperature. For the inner crust, we use the compressible liquid drop model for the first time to study the crustal properties in a magnetic environment. The inner crust properties, such as mass and charge number distribution, isospin asymmetry, cluster density, etc., show typical quantum oscillations (De Haas-van Alphen effect) sensitive to the magnetic field's strength. The density-dependent symmetry energy influences the magnetic inner crust like the field-free case. We study the probable modifications in the pasta structures and it is observed that their mass and thickness changes by $\sim 10-15 \%$ depending upon the magnetic field strength. The fundamental torsional oscillation mode frequency is investigated for the magnetized crust in the context of quasiperiodic oscillations (QPO) in soft gamma repeaters. The magnetic field strengths considered in this work influences only the EoS of outer and shallow regions of the inner crust, which results in no significant change in global neutron star properties. However, the outer crust mass and its moment of inertia increase considerably with increase in magnetic field strength.

Quantum Oscillation and Electronic Structure of Sn4As3 and Sn4P3

We report the magnetotransport properties and electronic structures of the single crystals of Sn4As3 and Sn4P3. The magnetization curves display strong de Haas–van Alphen oscillations at low temperatures and high magnetic fields. The oscillation frequencies and corresponding Fermi surfaces (FSs) are identified from the analysis of the oscillations. The in-plane magnetization of Sn4As3 shows the split of FSs induced by nonsymmetric spin–orbit interaction. The extracted cyclotron effective masses are very small and in the range 0.03–0.11 me. First-principles calculations reveal the electronic structures and topological properties. Large transverse magnetoresistance (MR) has also been observed in Sn4As3 and Sn4P3. The Hall measurements eliminate the possibility of electron–hole compensation. It is suggested that the large MR mainly originates from the open FSs.

Interdependence of External Magnetic and Temperature Effect on Thermodynamic Properties of GaAs Two Electron Quantum Dot

The particular interest of this paper is to investigate the impact of various values of temperature exposed to weak and strong magnetic field strength. A thermodynamic property's oscillatory change as a function of magnetic field effect (B) intensifies the quantization of electron orbits in a constant magnetic field intensity and is the primary contributor to the de Haas-van Alphen effects due to cyclotron frequency and its impact on localizing electron at circular region imposed with the magnetic field that is in contrary to the result of the temperature effect. Thus the interdependent effects of external magnetic field and temperature on thermodynamic properties are studied with harmonic oscillator potentials considering material parameters of GaAs quantum dot. The finite energy state is analytically solved using Nikiforov-Uvarov mathematical formalism. Moreover, the direct impact of the external magnetic fields and temperature on thermodynamic properties of the system is analyzed, and numerically simulated using matlab R2017a version. The dominance of temperature over the external magnetic field and vice versa effect is investigated, thus the value specific heat capacity fluctuated, while the equiponderate impact of temperature and magnetic field shows similar steady values of the specific heat capacity. The study clearly shows the interdependence of magnetic field and temperature affect thermodynamic quantities: partition function, mean energy, entropy, and specific heat capacity.

Multiple Magnetic Phases and Anomalous Hall Effect in Sb1.9Fe0.1Te2.85S0.15 Topological Insulators

Due to fundamental and technological concerns, investigating materials with topological magnetic structures has always been a focus of significant research. We explored Sb1.9Fe0.1Te2.85S0.15 where a unique combination of disordered glassy phases, competitive FM–AFM interactions, and nontrivial surface state coexisted at the same time. We have discussed the impact of those complicated magnetic phases upon the observed AHE in Sb1.9Fe0.1Te2.85S0.15 with magneto-transport studies. The AC susceptibility results demonstrate a shift in the freezing temperature with excitation frequency, the comprehensive analysis verifies the slower dynamics, and a nonzero Vogel–Fulcher temperature T0 suggests cluster spin glass. This, together with an intermediate value of the Mydosh parameter, provides an evidence for the formation of a cluster spin glass state in the present system. Topological frustrated magnets, which can host both magnetic frustrations and Dirac quasi-particles, are highly sought after class of compounds. Furthermore, as seen by the de Haas–van Alphen (dHvA) oscillation study, the fermiology deviates with doping and produces multiple Fermi pockets, revealing a rich complexity in the underlying electronic structure.

Shubnikov-de Haas (SdH) Oscillation in Self-Flux Grown Rhombohedral Single-Crystalline Bismuth

The historic de Haas-van Alphen effect observed in the late 1950s in CSIR-NPL by J.S. Dhillon and D. Shoenberg in pure bismuth and zinc metal is revisited in this article through a single-crystalline phase of bismuth crystal, which is observed in terms of resistivity as predicted by Shubnikov-de Haas (SdH) oscillations. The single crystal of bismuth is grown through solid-state reaction under an optimized heat treatment whose purity and structural phase are confirmed through XRD, SEM, and EDAX. The transport properties of single crystal show the presence of SdH oscillations from a temperature range of 2 to 10 K. The occurrence of oscillations in the transverse magnetic field confirms the presence of the Fermi surface. Landau level (LL) fan diagram reveals the presence of topological surface states and the Berry’s phase confirmation from temperature-dependent SdH oscillations, concluding the presence of a noble topological phase of bismuth exhibiting SdH oscillations.

Mechanical Detection of the De Haas-van Alphen Effect in Graphene.

In our work, we study the dynamics of a graphene Corbino disk supported by a gold mechanical resonator in the presence of a magnetic field. We demonstrate here that our graphene/gold mechanical structure exhibits a nontrivial resonance frequency dependence on the applied magnetic field, showing how this feature is indicative of the de Haas-van Alphen effect in the graphene Corbino disk. Relying on the mechanical resonances of the Au structure, our detection scheme is essentially independent of the material considered and can be applied for dHvA measurements on any conducting 2D material. In particular, the scheme is expected to be an important tool in studies of centrosymmetric transition metal dichalcogenide (TMD) crystals, shedding new light on hidden magnetization and interaction effects.

Quantum oscillations and weak anisotropic resistivity in the chiral fermion semimetal PdGa

We perform a detailed analysis of the magnetotransport and de Haas-van Alphen (dHvA) oscillations in crystal PdGa which is predicted to be a typical chiral Fermion semimetal from CoSi family holding a large Chern number. The unsaturated quadratic magnetoresistance (MR) and nonlinear Hall resistivity indicate that PdGa is a multi-band system without electron-hole compensation. Angle-dependent resistivity in PdGa shows weak anisotropy with twofold or threefold symmetry when the magnetic field rotates within the (1$\bar{1}$0) or (111) plane perpendicular to the current. Nine or three frequencies are extracted after the fast Fourier-transform analysis (FFT) of the dHvA oscillations with B//[001] or B//[011], respectively, which is confirmed to be consistent with the Fermi surfaces (FSs) obtained from first-principles calculations with spin-orbit coupling (SOC) considered.

Field-induced quasi-particle tunneling in the nodal-line semimetal HfSiS revealed by de Haas-van Alphen quantum oscillations

We present a de Haas--van Alphen quantum oscillation study of the Dirac nodal-line semimetal HfSiS up to 32 T to unravel the structure of the high-frequency magnetic breakdown spectrum that was previously obscured in transport experiments. Despite a threefold enhanced gap between adjacent electron and hole pockets relative to the sister compound ZrSiS, a large number of large-area magnetic breakdown orbits enclosing the nodal-loop are identified. All breakdown orbits are assigned by extracting their cyclotron masses. Moreover, one additional low-frequency magnetic breakdown orbit, previously absent in ZrSiS, is observed and attributed to the larger spin-orbit interaction in HfSiS.

Analysis of unconventional chiral fermions in a noncentrosymmetric chiral crystal PtAl

Symmetry protected nontrivial states in chiral topological materials hold immense potential for fundamental science and technological advances. Here, we report electrical transport, quantum oscillations, and electronic structure results of a single crystal of chiral quantum material PtAl. Based on the de Haas-van Alphen (dHvA) oscillations, we show that the smallest Fermi pocket $(\ensuremath{\alpha})$ possesses a nontrivial Berry phase $1.16\ensuremath{\pi}$. The band associated with this Fermi pocket carries a linear energy dispersion over a substantial energy window of $\ensuremath{\sim}700\phantom{\rule{0.16em}{0ex}}\mathrm{meV}$ that is further consistent with the calculated optical conductivity. First principles calculations unfold that PtAl is a higher fold chiral fermion semimetal where structural chirality drives the chiral fermions to lie at the high symmetry $\mathrm{\ensuremath{\Gamma}}$ and $R$ points of the cubic Brillouin zone. In the absence of spin orbit coupling, the band crossings at $\mathrm{\ensuremath{\Gamma}}$ and $\mathrm{R}$ points are three and fourfold degenerate with a chiral charge of $\ensuremath{-}2$ and $+2$, respectively. The inclusion of spin orbit coupling transforms these crossing points into four and sixfold degenerate points with a chiral charge of $\ensuremath{-}4$ and $+4$. Nontrivial surface states on the (001) surface connect the bulk projected chiral points through the long helical Fermi arcs that spread over the entire surface Brillouin zone.

Shubnikov-de Haas and de Haas-van Alphen oscillations in Czochralski grown CoSi single crystal

Anisotropic transport, Shubnikov-de Haas (SdH), and de Haas-van Alphen (dHvA) quantum oscillations studies are reported on a high-quality CoSi single crystal grown by the Czochralski method. Temperature-dependent resistivities indicate the dominating electron-electron scattering. Magnetoresistance (MR) at 2 K reaches 610% for and [01], whereas it is 500% for [01] and . A negative slope in field-dependent Hall resistivity suggests electrons are the majority carriers. The carrier concentration extracted from Hall conductivity indicates no electron–hole compensation. In 3D CoSi, the electron transport lifetime is found to be approximately in the same order as the quantum lifetime, whereas in 2D electron gas the long-range scattering drives the transport life much larger than the quantum lifetime. From MR and Hall SdH oscillations, the effective masses and Dingle temperatures have been calculated. The dHvA oscillation reveals three frequencies at 18 T (γ), 558 T (α) and 663 T (β), whereas, SdH oscillation results in only two frequencies α and β. The γ frequency observed in dHvA oscillation is a tiny hole pocket at the Γ point.

Fermi surface of the chiral topological semimetal PtGa

PtGa is a topological semimetal with giant spin-split Fermi arcs. Here, we report on angular-dependent de Haas–van Alphen (dHvA) measurements combined with band-structure calculations to elucidate the details of the bulk Fermi surface of PtGa. The strong spin–orbit coupling leads to eight bands crossing the Fermi energy that form a multitude of Fermi surfaces with closed extremal orbits and results in very rich dHvA spectra. The large number of experimentally observed dHvA frequencies make the assignment to the equally large number of calculated dHvA orbits challenging. Nevertheless, we find consistency between experiment and calculations verifying the topological character with maximal Chern number of the spin-split Fermi surface.

First Observation of the de Haas–van Alphen Effect and Fermi Surfaces in the Unconventional Superconductor UTe2

We report the first observation of the de Haas–van Alphen (dHvA) effect in the novel spin-triplet superconductor UTe2 using high quality single crystals with a high residual resistivity ratio (RRR) over 200. The dHvA frequencies, named α and β, are detected for the field directions between c- and a-axes. The frequency of branch β increases rapidly with the field angle tilted from c- to a-axis, while branch α splits, owing to the maximal and minimal cross-sectional areas from the same Fermi surface. Both dHvA branches, α and β reveal two kinds of cylindrical Fermi surfaces with a strong corrugation at least for branch α. The angular dependence of the dHvA frequencies is in very good agreement with that calculated by the generalized gradient approximation (GGA) method taking into account the on-site Coulomb repulsion of U = 2 eV. It indicates that the main Fermi surfaces are experimentally detected. The observed cyclotron effective masses are large in the range from 32 to 57 m0. They are approximately 10–20 times lager than the corresponding band masses, consistent with the mass enhancement obtained from the Sommerfeld coefficient, γ and the calculated density of states at the Fermi level. The local density approximation (LDA) calculations of ThTe2 assuming U4+ with the 5f2 localized model are in less agreement with our experimental results, in spite of the prediction for two cylindrical Fermi surfaces, suggesting a mixed valence states of U4+ and U3+ in UTe2.