Crystal growth and quantum oscillations in the topological chiral semimetal CoSi

Xu, Xitong; Wang, Xirui; Cochran, Tyler A.; Sanchez, Daniel S.; Chang, Guoqing; Belopolski, Ilya; Wang, Guangqiang; Liu, Yiyuan; Tien, Hung-Ju; Gui, Xin; Xie, Weiwei; Hasan, M. Zahid; Chang, Tay Rong; Jia, Shuang

doi:10.1103/physrevb.100.045104

Cited by 62 publications

(62 citation statements)

References 63 publications

(106 reference statements)

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“…CDWs or SDWs were observed in many superconductors, for example Pb and Nb, HfTe 3 or NbSe 2 , and the coexistence or competition between these electronic phases is debated. Another closely related phenomena is the phonon drag effect that was recently found in undoped CoSi . The phonon drag effect assumes momentum transfer from phonon diffusive flow to conduction electrons in a temperature gradient.…”

Section: Resultsmentioning

confidence: 94%

“…In a recent report on undoped CoSi, distinct quantum oscillations were observed in magneto‐Seebeck and Nernst effect characterization above 2 T at temperatures below 5.9 K. But like in the data presented here, no magento‐resistance quantum oscillations were reported in ref. .…”

Section: Resultsmentioning

confidence: 99%

“…A CDW is connected to a structural distortion in the crystal lattice. [28] The phonon drag effect assumes momentum transfer from phonon diffusive flow to conduction electrons in a temperature gradient. [23] CDWs or SDWs were observed in many superconductors, [23] for example Pb and Nb, [24] HfTe 3 [25] or NbSe 2 , [26] and the coexistence or competition between these electronic phases is debated.…”

Section: Formation Of a Potential Cdw Phase Evidenced In The Temperatmentioning

confidence: 99%

“…This effect is caused by a phase shift between the time-reversed scattering paths of a conducting electron near zero magnetic field, which leads to an increase in the conductivity. [28]. [38] Quantum oscillations were not observed.…”

Section: Field (Sketches Inmentioning

confidence: 99%

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Signatures of a Charge Density Wave Phase and the Chiral Anomaly in the Fermionic Material Cobalt Monosilicide CoSi

Schnatmann

Geishendorf

Lammel

et al. 2019

Adv Elect Materials

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to the emerging class of materials with non-trivial electronic band structure like topological insulators, Dirac or Weyl materials, featuring different topologically protected electronic states. In Weyl materials, these topologically protected electronic states are highly stable quasiparticles in the bulk, known as Weyl fermions, that were first predicted by Hermann Weyl in 1929. [1] These Weyl fermions carry a non-zero chiral charge and always appear in pairs. In a common Weyl material, this chiral charge is ±1; hence, the total chiral charge is zero. In contrast, the fermionic materials host Weyl fermions that are degenerated and carry a higher chiral charge. Remarkably, recently long Fermi arcs were observed in the fermionic material CoSi by Rao et al. [2] Also, Sanchez et al. [3] discovered helicoid-arc quantum states in CoSi.A necessary condition for the existence of Weyl fermions is a broken space or time inversion symmetry. The chiral charge of the material strongly depends on the space group of the crystal structure. CoSi has a cubic B20 crystal structure (space group 198 P2 1 3) with broken space inversion symmetry. This space group was predicted to host sixfold degenerated Weyl fermions. [4] In CoSi, the Weyl fermions carry a chiral charge of up to ±4. In detail, spin 1 excitations with a chiral charge of ±2 and spin 3/2 excitations with a chiral charge of ±4 (Rarita-Schwinger-Weyl fermions) were predicted. [5,6] Electrical transport experiments are a powerful tool to probe the energy spectrum of a material and thereby the specific nature of Weyl fermions. Topological states are massless due to the linear dispersion relation, and thus have an extremely high mobility. While often superimposed by the normal band transport, contributions of the Weyl fermions increase the total electrical conductivity. Consequently, the emerging class of materials with non-trivial electronic band structure has a large overlap with other classes of functional materials like the class of thermoelectric materials. [7] This also holds for CoSi. [5,8,9] Interestingly, related silicides like MnSi, [10] Fe 0.75 Co 0.25 Si [11] and germanides like Fe 1 −x Co x Ge [12,13] also feature skyrmion states.In general, Weyl materials show characteristic quantum effects in the transport, resulting for example in quantum Materials with topological electronic states have emerged as one of the most exciting discoveries of condensed quantum matter, hosting quasiparticles with extremely low effective mass and high mobility. Weyl materials contain such topological states in the bulk and additionally have a non-trivial chiral charge. However, despite known quantum effects caused by these chiral states, the interplay between chiral states, and a charge density wave phase, an ordering of the electrons to a correlated phase is not experimentally explored. Indications for the formation of a charge density wave phase in the Weyl material cobalt monosilicide CoSi are observed. Furthermore, the typical signatures of the charge density wave phase together...

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Formation Of a Potential Cdw Phase Evidenced In The Temperatmentioning

confidence: 99%

Section: Field (Sketches Inmentioning

confidence: 99%

See 2 more Smart Citations

Signatures of a Charge Density Wave Phase and the Chiral Anomaly in the Fermionic Material Cobalt Monosilicide CoSi

Schnatmann

Geishendorf

Lammel

et al. 2019

Adv Elect Materials

View full text Add to dashboard Cite

show abstract

“…The ampule was heated to 1100 ∘ C with a speed of about 150 ∘ C/h. After soaking at 1100 ∘ C for 10 h, the ampule was cooled down to 700 ∘ C at the rate of 2 ∘ C/h, and the excess flux was centrifuged out at that temperature to get several single crystals with large (111) facet 43 . Crystals larger than 2 × 2 mm were picked for THz emission experiments.…”

Section: Methodsmentioning

confidence: 99%

Giant topological longitudinal circular photo-galvanic effect in the chiral multifold semimetal CoSi

et al. 2021

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The absence of mirror symmetry, or chirality, is behind striking natural phenomena found in systems as diverse as DNA and crystalline solids. A remarkable example occurs when chiral semimetals with topologically protected band degeneracies are illuminated with circularly polarized light. Under the right conditions, the part of the generated photocurrent that switches sign upon reversal of the light’s polarization, known as the circular photo-galvanic effect, is predicted to depend only on fundamental constants. The conditions to observe quantization are non-universal, and depend on material parameters and the incident frequency. In this work, we perform terahertz emission spectroscopy with tunable photon energy from 0.2 –1.1 eV in the chiral topological semimetal CoSi. We identify a large longitudinal photocurrent peaked at 0.4 eV reaching ~550 μ A/V2, which is much larger than the photocurrent in any chiral crystal reported in the literature. Using first-principles calculations we establish that the peak originates only from topological band crossings, reaching 3.3 ± 0.3 in units of the quantization constant. Our calculations indicate that the quantized circular photo-galvanic effect is within reach in CoSi upon doping and increase of the hot-carrier lifetime. The large photo-conductivity suggests that topological semimetals could potentially be used as novel mid-infrared detectors.

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Large Transverse and Longitudinal Magneto‐Thermoelectric Effect in Polycrystalline Nodal‐Line Semimetal Mg₃Bi₂

et al. 2022

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Topological semimetals provide new opportunities for exploring new thermoelectric phenomena, because of their exotic and nontrivial electronic structure topology around the Fermi surface. In this study, we report on the discovery of giant transverse and longitudinal magneto-thermoelectric (MTE) effects in Mg3Bi2, which is predicted to be a type-II nodal-line semimetal in the absence of spin-orbit coupling (SOC). The maximum transverse power factor is 2182 μWm −1 K −2 at 13.5 K and 6 Tesla. The longitudinal power factor reaches up to 3043 μWm −1 K −2 at 15 K and 13 Tesla, which is 20 times higher than in a zero-strength magnetic field and is also comparable to state-of-the-art MTE materials. By compensating Mg loss in the Mg-rich conditions for turning carrier concentration, the sample obtained in this work shows a large linear non-saturating magnetoresistance of 940% under a field of 14 Tesla. This is a two-orders-of-magnitude increase with respect to the normal Mg-deficiency Mg3Bi2 sample. Using density functional calculations, we attribute the underlying mechanism to the parent nodal-line electronic structure without SOC and the anisotropic Fermi surface shape with SOC, highlighting the essential role of high carrier mobility and open electron orbits in moment space. Our work offers a new avenue toward highly efficient thermoelectric materials through the design of Fermi surfaces with special topological electronic structures in novel quantum materials.

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Crystal growth and quantum oscillations in the topological chiral semimetal CoSi

Cited by 62 publications

References 63 publications

Signatures of a Charge Density Wave Phase and the Chiral Anomaly in the Fermionic Material Cobalt Monosilicide CoSi

Signatures of a Charge Density Wave Phase and the Chiral Anomaly in the Fermionic Material Cobalt Monosilicide CoSi

Giant topological longitudinal circular photo-galvanic effect in the chiral multifold semimetal CoSi

Large Transverse and Longitudinal Magneto‐Thermoelectric Effect in Polycrystalline Nodal‐Line Semimetal Mg₃Bi₂

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Crystal growth and quantum oscillations in the topological chiral semimetal CoSi

Cited by 62 publications

References 63 publications

Signatures of a Charge Density Wave Phase and the Chiral Anomaly in the Fermionic Material Cobalt Monosilicide CoSi

Signatures of a Charge Density Wave Phase and the Chiral Anomaly in the Fermionic Material Cobalt Monosilicide CoSi

Giant topological longitudinal circular photo-galvanic effect in the chiral multifold semimetal CoSi

Large Transverse and Longitudinal Magneto‐Thermoelectric Effect in Polycrystalline Nodal‐Line Semimetal Mg3Bi2

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Large Transverse and Longitudinal Magneto‐Thermoelectric Effect in Polycrystalline Nodal‐Line Semimetal Mg₃Bi₂