Unusual Temperature Dependence of Band Dispersion in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Ba</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mi>Fe</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Ru</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mo stretchy="false">)</mml:mo><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>and its Consequ

Dhaka, R. S.; Hahn, Steven; Razzoli, E.; Jiang, Rui; Shi, M.; Harmon, B. N.; Thaler, A.; Bud’ko, Sergey L.; Canfield, Paul C.; Kaminski, Adam

doi:10.1103/physrevlett.110.067002

Cited by 53 publications

(61 citation statements)

References 51 publications

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“…We speculate that the temperature induced shift of the chemical potential and resulting change of the relative size of electron and hole pockets causes the large magnetoresistance effect to vanish at elevated temperatures. Reported here change of the chemical potential upon increase of the temperature is not expected for simple materials, but was observed previously in iron arsenic high temperature superconductors [29], where both electron and hole pockets are located in close proximity of E F .…”

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confidence: 83%

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Temperature-Induced Lifshitz Transition inWTe2

Wu¹,

Jo²,

Ochi³

et al. 2015

Phys. Rev. Lett.

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We use ultra-high resolution, tunable, VUV laser-based, angle-resolved photoemission spectroscopy (ARPES) and temperature and field dependent resistivity and thermoelectric power (TEP) measurements to study the electronic properties of WTe2, a compound that manifests exceptionally large, temperature dependent magnetoresistance. The temperature dependence of the TEP shows a change of slope at T=175 K and the Kohler rule breaks down above 70-140 K range. The Fermi surface consists of two electron pockets and two pairs of hole pockets along the X-Γ-X direction. Upon increase of temperature from 40K, the hole pockets gradually sink below the chemical potential. Like BaFe2As2, WTe2 has clear and substantial changes in its Fermi surface driven by modest changes in temperature. In WTe2, this leads to a rare example of temperature induced Lifshitz transition, associated with the complete disappearance of the hole pockets. These dramatic changes of the electronic structure naturally explain unusual features of the transport data.The discovery of giant magnetoresistance (GMR) in Fe/Cr superlattice [1,2], opened a new era of applications in magnetic field sensors, read heads in high density hard disks, random access memories, and galvanic isolators [3]. In the quest of achieving large MR in crystalline materials, a class of manganese oxides colossal magnetoresistance (CMR) materials was discovered that exhibits a large change in resistance with applied magnetic fields but only at low temperatures [4][5][6] The temperature dependent electrical resistivity, Hall coefficient and thermoelectric power of tungstenditelluride have been known for several decades [13] and a three-carrier semi-metal band model [13,14] was proposed to explain the electrical resistivity. Later on, density-functional based augmented spherical wave (ASW) electronic structure calculations and relatively low resolution ARPES [15] were used to study the electronic properties of WTe 2 and further supported the semimetallic nature of this material. However due to the low resolution of these early experiments, no details about the Fermi surface or band dispersion were obtained. Recent ARPES [11] and quantum oscillation [16] results revealed presence of small electron and hole pockets of roughly similar size. These findings were consistent with carrier compensation mechanism as the primary source of the MR effect [10,12]. Furthermore, this study also reported a change of the size of the Fermi pockets between 20K and 100K. More recently, Jiang et al.[17] claimed observation of strong spin-orbital coupling effect and proposed that the backscattering protection mechanism also may play a role in the large nonsaturating MR of WTe 2 .In this letter, we present the results from temperature dependent transport and ultra-high resolution, tunable VUV laser based ARPES[18] measurements. Our data show that there are two electron pockets and four hole pockets along the X-Γ-X direction and a fully occupied light "hole" band at the center of the Brillouin Zone (BZ) located j...

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confidence: 83%

“…On the other hand, a temperature induced Lifshitz transition in the absence of a structure or magnetic phase transition is extremely rare. chemical potential and resulting changes in size of both pockets were observed [29].) The temperature dependent TEP, in particular the change of slope of ∂S/∂T at ∼ 160 K (Fig.…”

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confidence: 99%

Temperature-Induced Lifshitz Transition inWTe2

Wu¹,

Jo²,

Ochi³

et al. 2015

Phys. Rev. Lett.

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217

202

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“…57,58 Also relevant here is the AFM transition in CaCo 1.86 As 2 at about 52 K observed in our χ(T ) measurements. Therefore, to see whether the band structure changes across this transition, we have performed additional T -dependent ARPES measurements.…”

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confidence: 99%

Physical properties of metallic antiferromagnetic CaCo1.86 As2 single crystals

et al. 2014

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X-ray powder diffraction (XRD), magnetic susceptibility χ, isothermal magnetization M , heat capacity Cp and in-plane electrical resistivity ρ measurements as a function of temperature T and magnetic field H are presented for CaCo1.86As2 single crystals. The electronic structure is probed by angle-resolved photoemission spectroscopy (ARPES) measurements of CaCo1.86As2 and by full-potential linearized augmented-plane-wave calculations for the supercell Ca8Co15As16 (CaCo1.88As2). Our XRD crystal structure refinement is consistent with the previous combined refinement of x-ray and neutron powder diffraction data showing a collapsed-tetragonal ThCr2Si2-type structure with 7(1)% vacancies on the Co sites corresponding to the composition CaCo1.86As2 [D. G. Quirinale et al., Phys. Rev. B 88, 174420 (2013)]. The anisotropic χ(T ) data are consistent with the magnetic neutron diffraction data of Quirianale et al. that demonstrate the presence of A-type collinear antiferromagnetic order below the Néel temperature TN = 52(1) K with the easy axis being the tetragonal c axis. However, no clear evidence from the ρ(T ) and Cp(T ) data for a magnetic transition at TN is observed. A metallic ground state is demonstrated from the band calculations and the ρ(T ), Cp(T ) and ARPES data, and spin-polarized calculations indicate a competition between the A-type AFM and FM ground states. The Cp(T ) data exhibit a large Sommerfield electronic coefficient reflecting a large density of states at the Fermi energy D(EF) that is enhanced compared with the band structure calculation where the bare D(EF) arises from Co 3d bands. At 1.8 K the M (H) data for H c exhibit a well-defined first-order spin-flop transition at an applied field of 3.5 T. The small ordered moment of ≈ 0.3 µB/Co obtained from the M (H) data at low T , the large exchange enhancement of χ and the lack of a self-consistent interpretation of the χ(T ) and M (H, T ) data in terms of a local moment Heisenberg model together indicate that the magnetism of CaCo1.86As2 is itinerant.

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“…Then, conversely, using known changes to the band structure upon variation of the pnictogen height h above the iron plane, we can estimate the amplitude of the coherent A 1g (As) oscillation from our results. DFT predicts a 'deformation potential' ∆µ/∆h for BaFe 2 As 2 of about −2 eV/Å [33,36]. The typical renormalization factor of 3-5 for iron pnictide bands calculated within the local density approximation [37][38][39] brings this value into good agreement with an experimental value of −0.58 eV/Å derived from ARPES band shifts and measured changes of the average pnictogen height in BaFe 2 (As 1−x P x ) 2 [40][41][42].…”

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Ultrafast Modulation of the Chemical Potential inBaFe2As2by Coherent Phonons

et al. 2014

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Time-and angle-resolved extreme ultraviolet photoemission spectroscopy is used to study the electronic structure dynamics in BaFe2As2 around the high-symmetry points Γ and M . A global oscillation of the Fermi level at the frequency of the A1g(As) phonon mode is observed. It is argued that this behavior reflects a modulation of the effective chemical potential in the photoexcited surface region that arises from the high sensitivity of the band structure near the Fermi level to the A1g phonon mode combined with a low electron diffusivity perpendicular to the layers. The results establish a novel way to tune the electronic properties of iron pnictides: coherent control of the effective chemical potential. The results further suggest that the equilibration time for the effective chemical potential needs to be considered in the ultrafast electronic structure dynamics of materials with weak interlayer coupling.PACS numbers: 74.25. Jb,74.70.Xa, Time-resolved optical and photoemission spectroscopies have become important tools to probe the microscopic details of electron-phonon coupling. The prime example is the reliable determination of the coupling parameter from measured relaxation times of excited electrons [1][2][3][4][5][6]. More recently, time-resolved spectroscopies have provided novel insights into the transient behavior of electronically ordered phases, specifically chargedensity waves and superconductivity, in which electronphonon coupling plays a prominent role [7][8][9][10][11][12][13][14].A particularly intriguing aspect of electron-phonon coupling often observed in pump-probe spectroscopy is the generation of coherent optical phonons [15] and their subsequent modulation of electronic properties. This effect not only provides a powerful means to study femtosecond lattice dynamics [16], but can also be used to coherently control the electronic structure of materials. Through time-and angle-resolved photoemission spectroscopy (trARPES), coherent phonon-induced oscillations of electron binding energies are now well known [7,8,[17][18][19][20], and in a recent study on the semimetal Bi it was also shown how the underlying momentumdependent deformation potential can be determined from such oscillations with the help of density functional theory (DFT) [19]. Since the electrons with the lowest binding energies determine material properties and collective phenomena, the physics will become particularly interesting if transient band shifts and renormalizations are induced near the chemical potential, which itself may then have to adjust to preserve charge neutrality. However, transient band renormalization effects in the vicinity of the chemical potential have so far only been reported for charge-density-wave systems [7,8,12,13].Iron pnictides should provide a fertile field for the study of coherent phonon-induced electronic effects near the chemical potential. Firstly, their electronic, magnetic, and superconducting properties are well known to be highly sensitive to the distance between the iron and pnictogen pl...

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Unusual Temperature Dependence of Band Dispersion inBa(Fe1−xRux)2As2and its Consequ

Cited by 53 publications

References 51 publications

Temperature-Induced Lifshitz Transition inWTe2

Temperature-Induced Lifshitz Transition inWTe2

Physical properties of metallic antiferromagnetic CaCo1.86 As2 single crystals

Ultrafast Modulation of the Chemical Potential inBaFe2As2by Coherent Phonons

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