Temperature dependence of quantum oscillations from non-parabolic dispersions

AbstractThe phase offset of quantum oscillations is commonly used to experimentally diagnose topologically nontrivial Fermi surfaces. This methodology, however, is inconclusive for spin-orbit-coupled metals where π-phase-shifts can also arise from non-topological origins. Here, we show that the linear dispersion in topological metals leads to a T2-temperature correction to the oscillation frequency that is absent for parabolic dispersions. We confirm this effect experimentally in the Dirac semi-metal Cd3As2 and the multiband Dirac metal LaRhIn5. Both materials match a tuning-parameter-free theoretical prediction, emphasizing their unified origin. For topologically trivial Bi2O2Se, no frequency shift associated to linear bands is observed as expected. However, the π-phase shift in Bi2O2Se would lead to a false positive in a Landau-fan plot analysis. Our frequency-focused methodology does not require any input from ab-initio calculations, and hence is promising for identifying correlated topological materials.

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Nontrivial quantum oscillation geometric phase shift in a trivial band

Science Advances ◽

10.1126/sciadv.aax6550 ◽

2019 ◽

Vol 5 (10) ◽

pp. eaax6550

Author(s):

Biswajit Datta ◽

Pratap Chandra Adak ◽

Li-kun Shi ◽

Kenji Watanabe ◽

Takashi Taniguchi ◽

...

Keyword(s):

Phase Shift ◽

Quantum Oscillation ◽

Oscillation Phase ◽

Berry's Phase ◽

Fermi Surfaces ◽

Quantum Oscillations ◽

Berry’S Phase ◽

Topological Quantum ◽

Linear Band ◽

Trilayer Graphene

Quantum oscillations provide a notable visualization of the Fermi surface of metals, including associated geometrical phases such as Berry’s phase, that play a central role in topological quantum materials. Here we report the existence of a new quantum oscillation phase shift in a multiband system. In particular, we study the ABA-trilayer graphene, the band structure of which is composed of a weakly gapped linear Dirac band, nested within a quadratic band. We observe that Shubnikov-de Haas (SdH) oscillations of the quadratic band are shifted by a phase that sharply departs from the expected 2π Berry’s phase and is inherited from the nontrivial Berry’s phase of the linear band. We find this arises due to an unusual filling enforced constraint between the quadratic band and linear band Fermi surfaces. Our work indicates how additional bands can be exploited to tease out the effect of often subtle quantum mechanical geometric phases.

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Layer- and gate-tunable spin-orbit coupling in a high-mobility few-layer semiconductor

Science Advances ◽

10.1126/sciadv.abe2892 ◽

2021 ◽

Vol 7 (5) ◽

pp. eabe2892

Author(s):

Dmitry Shcherbakov ◽

Petr Stepanov ◽

Shahriar Memaran ◽

Yaxian Wang ◽

Yan Xin ◽

...

Keyword(s):

Electric Field ◽

High Mobility ◽

Orbit Coupling ◽

Spin Splitting ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Quantum Oscillations ◽

Out Of Plane ◽

Order Of Magnitude ◽

Spin Degeneracy

Spin-orbit coupling (SOC) is a relativistic effect, where an electron moving in an electric field experiences an effective magnetic field in its rest frame. In crystals without inversion symmetry, it lifts the spin degeneracy and leads to many magnetic, spintronic, and topological phenomena and applications. In bulk materials, SOC strength is a constant. Here, we demonstrate SOC and intrinsic spin splitting in atomically thin InSe, which can be modified over a broad range. From quantum oscillations, we establish that the SOC parameter α is thickness dependent; it can be continuously modulated by an out-of-plane electric field, achieving intrinsic spin splitting tunable between 0 and 20 meV. Unexpectedly, α could be enhanced by an order of magnitude in some devices, suggesting that SOC can be further manipulated. Our work highlights the extraordinary tunability of SOC in 2D materials, which can be harnessed for in operando spintronic and topological devices and applications.

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Phase shift in skyrmion crystals

Nature Communications ◽

10.1038/s41467-021-27083-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Satoru Hayami ◽

Tsuyoshi Okubo ◽

Yukitoshi Motome

Keyword(s):

Phase Shift ◽

Relative Phase ◽

Exchange Interactions ◽

Thermal Fluctuations ◽

Coupled Systems ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Spin Density Waves ◽

Vortex Crystal ◽

Spin Texture

AbstractThe magnetic skyrmion crystal is a periodic array of a swirling topological spin texture. Since it is regarded as an interference pattern by multiple helical spin density waves, the texture changes with the relative phase shifts among the constituent waves. Although such a phase degree of freedom is relevant to not only magnetism but also transport properties, its effect has not been elucidated thus far. We here theoretically show that a phase shift in the skyrmion crystals leads to a tetra-axial vortex crystal and a meron-antimeron crystal, both of which show a staggered pattern of the scalar spin chirality and give rise to nonreciprocal transport phenomena without the spin-orbit coupling. We demonstrate that such a phase shift can be driven by exchange interactions between the localized spins, thermal fluctuations, and long-range chirality interactions in spin-charge coupled systems. Our results provide a further diversity of topological spin textures and open a new field of emergent electromagnetism by the phase shift engineering.

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Theoretical prediction of the spin-orbit splitting in the NCO, NCS, HCCO and HCCS radicals

The Journal of Chemical Physics ◽

10.1063/1.473206 ◽

1997 ◽

Vol 106 (1) ◽

pp. 436-437 ◽

Cited By ~ 26

Author(s):

Péter G. Szalay ◽

Jean-Philippe Blaudeau

Keyword(s):

Theoretical Prediction ◽

Spin Orbit ◽

Orbit Splitting ◽

Spin Orbit Splitting

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Phase-Shift Analysis of Elastic pp Scattering at High Energies and Catastrophic Energy-Dependence of Spin-Orbit Interaction

Few-Body Problems in Physics ’99 - Few-Body Systems ◽

10.1007/978-3-7091-6287-3_81 ◽

2000 ◽

pp. 457-461

Author(s):

J. Nagata ◽

K. Harada ◽

H. Yoshino ◽

M. Matsuda

Keyword(s):

Phase Shift ◽

Energy Dependence ◽

Phase Shift Analysis ◽

Orbit Interaction ◽

Spin Orbit ◽

Spin Orbit Interaction ◽

High Energies ◽

Shift Analysis

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Type-II Ising pairing in few-layer stanene

Science ◽

10.1126/science.aax3873 ◽

2020 ◽

Vol 367 (6485) ◽

pp. 1454-1457 ◽

Cited By ~ 13

Author(s):

Joseph Falson ◽

Yong Xu ◽

Menghan Liao ◽

Yunyi Zang ◽

Kejing Zhu ◽

...

Keyword(s):

Symmetry Breaking ◽

Upper Critical Field ◽

Distinct Type ◽

Inversion Symmetry ◽

Spin Orbit Coupling ◽

Type Ii ◽

Spin Orbit ◽

Pairing Mechanism ◽

Topological Materials ◽

Ultralow Temperature

Spin-orbit coupling has proven indispensable in the realization of topological materials and, more recently, Ising pairing in two-dimensional superconductors. This pairing mechanism relies on inversion symmetry–breaking and sustains anomalously large in-plane polarizing magnetic fields whose upper limit is predicted to diverge at low temperatures. Here, we show that the recently discovered superconductor few-layer stanene, epitaxially strained gray tin (α-Sn), exhibits a distinct type of Ising pairing between carriers residing in bands with different orbital indices near the Γ-point. The bands are split as a result of spin-orbit locking without the participation of inversion symmetry–breaking. The in-plane upper critical field is strongly enhanced at ultralow temperature and reveals the predicted upturn.

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Topological Fulde–Ferrell superfluids of a spin–orbit coupled Fermi gas

International Journal of Modern Physics B ◽

10.1142/s0217979215300017 ◽

2014 ◽

Vol 29 (01) ◽

pp. 1530001 ◽

Cited By ~ 22

Author(s):

Yong Xu ◽

Chuanwei Zhang

Keyword(s):

Momentum Space ◽

Cold Atom ◽

Fermi Gas ◽

Real Space ◽

Temperature Phase ◽

Majorana Fermions ◽

Three Dimension ◽

Spin Orbit ◽

Linear Dispersion ◽

Weyl Fermions

Topological Fermi superfluids have played the central role in various fields of physics. However, all previous studies focus on the cases where Cooper pairs have zero center-of-mass momenta (i.e., normal superfluids). The topology of Fulde–Ferrell (FF) superfluids with nonzero momentum pairings have never been explored until recent findings that FF superfluids in a spin–orbit (SO) coupled Fermi gas can accommodate Majorana fermions in real space in low dimensions and Weyl fermions in momentum space in three dimension. In this review, we first discuss the mechanism of pairings in SO coupled Fermi gases in optical lattices subject to Zeeman fields, showing that SO coupling as well as Zeeman fields enhance FF states while suppress Larkin–Ovchinnikov states. We then present the low temperature phase diagram including both FF superfluids and topological FF superfluids phases in both two dimension and three dimension. In one dimension, Majorana fermions as well as phase dependent order parameter are visualized. In three dimension, we show the properties of Weyl fermions in momentum space such as anisotropic linear dispersion, Fermi arch, and gaplessness away from k⊥ = 0. Finally, we discuss some possible methods to probe FF superfluids and topological FF superfluids in cold atom systems.

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