P. Richard

Two pseudogaps with different energy scales at the antinode of the high-temperature Bi $_{2}$ Sr $_{2}$ CuO $_{6}$ superconductor using angle-resolved photoemission spectroscopy

K. Nakayama, T. Sato, Y. -M. Xu +8

We have performed high-resolution angle-resolved photoemission spectroscopy on single-layered cuprate Bi $_{2}$ Sr $_{2}$ CuO $_{6}$ to clarify the origin of the pseudogap. By using various p…

Angle-resolved photoemission studies of the superconducting gap symmetry in Fe-based superconductors

Y. -B. Huang, P. Richard, X. -P. Wang +2

The superconducting gap is the fundamental parameter that characterizes the superconducting state, and its symmetry is a direct consequence of the mechanism responsible for Cooper…

physics.data-an2011

A precise method for visualizing dispersive features in image plots

P. Zhang, P. Richard, T. Qian +3

In order to improve the advantages and the reliability of the second derivative method in tracking the position of extrema from experimental curves, we develop a novel analysis met…

Robustness of topological states to lattice instability in non-symmorphic topological insulator KHgSb

D. Chen, T. T. Zhang, C. J. Yi +8

We report a polarized Raman scattering study of non-symmorphic topological insulator KHgSb with hourglass-like electronic dispersion. Supported by theoretical calculations, we show…

Electronic structure of optimally doped pnictide Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ : a comprehensive ARPES investigation

H. Ding, K. Nakayama, P. Richard +13

We have conducted a comprehensive angle-resolved photoemission study on the normal state electronic structure of the Fe-based superconductor Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ . We hav…

Observation of strong-coupling pairing with weakened Fermi-surface nesting at optimal hole doping in Ca $_{0.33}$ Na $_{0.67}$ Fe $_{2}$ As $_{2}$

Y. -B. Shi, Y. -B. Huang, X. -P. Wang +12

We report an angle-resolved photoemission investigation of optimally-doped Ca $_{0.33}$ Na $_{0.67}$ Fe $_{2}$ As $_{2}$ . The Fermi surface topology of this compound is similar to that of the…

Observation of Dirac-like band dispersion in LaAgSb $_{2}$

X. Shi, P. Richard, Kefeng Wang +10

We present a combined angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations study of the electronic structure of LaAgSb $_{2}$ in the entire first Brillo…

Observation of two distinct $d_{x z} / d_{y z}$ band splittings in FeSe

P. Zhang, T. Qian, P. Richard +10

We report the temperature evolution of the detailed electronic band structure in FeSe single-crystals measured by angle-resolved photoemission spectroscopy (ARPES), including the d…

Evolution from incoherent to coherent electronic states and its implications to superconductivity in FeTe1-xSex

E. Ieki, K. Nakayama, Y. Miyata +14

We have performed systematic angle-resolved photoemission spectroscopy (ARPES) of iron-chalcogenide superconductor FeTe1-xSex to elucidate the electronic states relevant to the sup…

Observation of an electron band above the Fermi level in FeTe $_{0.55}$ Se $_{0.45}$ from \emph{in-situ} surface doping

P. Zhang, P. Richard, N. Xu +7

We used \emph{in-situ} potassium (K) evaporation to dope the surface of the iron-based superconductor FeTe $_{0.55}$ Se $_{0.45}$ . The systematic study of the bands near the Fermi lev…

Orbital Characters Determined from Fermi Surface Intensity Patterns using Angle-Resolved Photoemission Spectroscopy

X. -P. Wang, P. Richard, Y. -B. Huang +10

In order to determine the orbital characters on the various Fermi surface pockets of the Fe-based superconductors Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ and FeSe $_{0.45}$ Te $_{0.55}$ ,…

Raman scattering investigation of the electron-phonon coupling in superconducting Nd(O,F)BiS $_{2}$

S. F. Wu, P. Richard, X. B. Wang +5

We have performed polarized Raman scattering measurements on the newly discovered superconductor Nd(O,F)BiS $_{2}$ ( $T_{c} = 4$ K). We observe 2 Raman active modes, with frequencies in…

cond-mat.str-el2016

Stress-induced nematicity in EuFe2As2 studied by phononic Raman spectroscopy

W. -L. Zhang, Athena S. Sefat, H. Ding +2

We use polarized Raman scattering to study the structural phase transition in EuFe2As2, the parent compound of the 122-ferropnictide superconductors. The in-plane lattice anisotrop…

cond-mat.str-el2016

Raman scattering study of spin-density-wave-induced anisotropic electronic properties in AFe2As2 (A=Ca,Eu)

W. -L. Zhang, Z. P. Yin, A. Ignatov +6

We present a polarization-resolved and temperature-dependent Raman scattering study of AFe2As2 (A = Ca, Eu). In the spin-density-wave (SDW) phase, spectral weight redistribution is…

Observation of Weyl nodes in TaAs

B. Q. Lv, N. Xu, H. M. Weng +14

In 1929, H. Weyl proposed that the massless solution of Dirac equation represents a pair of new type particles, the so-called Weyl fermions [1]. However the existence of them in pa…

cond-mat.supr-con2010

Electron-Hole Asymmetry in Superconductivity of Pnictides Originated from the Observed Rigid Chemical Potential Shift

M. Neupane, P. Richard, Y. -M. Xu +12

We have performed a systematic photoemission study of the chemical potential shift as a function of carrier doping in a pnictide system based on BaFe $_{2}$ As $_{2}$ . The experimentally…

cond-mat.str-el2013

Observation of well-defined quasi-particle over a wide energy range in quasi-2D system

L. -L. Jia, Z. -H. Liu, Y. -P. Cai +12

We report the observation by angle-resolved photoemission spectroscopy measurements of a highly anisotropic Dirac-cone structure in high quality SrMnBi2 crystals. We reveal a well-…

cond-mat.supr-con2019

Observation of topological transition in high-T $_{c}$ superconductor FeTe $_{1 - x}$ Se $_{x}$ /SrTiO $_{3}$ (001) monolayers

X. -L. Peng, Y. Li, X. -X. Wu +12

Superconductors with topological surface or edge states have been intensively explored for the prospect of realizing Majorana bound states, which obey non-Abelian statistics and ar…

Tuning electronic correlations in transition metal pnictides: chemistry beyond the valence count

E. Razzoli, C. E. Matt, M. Kobayashi +14

The effects of electron-electron correlations on the low-energy electronic structure and their relationship with unconventional superconductivity are central aspects in the researc…

Fermi surface nesting induced strong pairing in iron-based superconductors

K. Terashima, Y. Sekiba, J. H. Bowen +10

The discovery of high-temperature superconductivity in iron pnictides raised the possibility of an unconventional superconducting mechanism in multiband materials. The observation…

Experimental Observation of Three-Component 'New Fermions' in Topological Semimetal MoP

B. Q. Lv, Z. -L. Feng, Q. -N. Xu +10

Condensed matter systems can host quasiparticle excitations that are analogues to elementary particles such as Majorana, Weyl, and Dirac fermions. Recent advances in band theory ha…

Camelback-shaped band reconciles heavy electron behavior with weak electronic Coulomb correlations in superconducting TlNi2Se2

N. Xu, C. E. Matt, P. Richard +16

Using high-resolution photoemission spectroscopy and first-principles calculations, we characterize superconducting TlNi $_{2}$ Se $_{2}$ as a material with weak electronic Coulomb correl…

cond-mat.mtrl-sci2012

Observation of momentum space semi-localization in Si-doped $I^^{2}$ -Ga $_{2}$ O $_{3}$

P. Richard, T. Sato, S. Souma +7

We performed an angle-resolved photoemission spectroscopy study of Si-doped $I^^{2}$ -Ga $_{2}$ O $_{3}$ . We observed very small photoemission intensity near the Fermi level corresponding to n…

cond-mat.supr-con2010

Fermiology of Sr4V2O6Fe2As2: Quasi-Nested Fe vs Mott-Insulating V Orbitals

T. Qian, N. Xu, Y. -B. Shi +14

We have performed an angle-resolved photoemission spectroscopy study of a new iron-based superconductor Sr4V2O6Fe2As2. While V 3d orbitals are found to be in a Mott insulator state…

Observation of Open-Orbit Fermi Surface Topology in Extremely Large Magnetoresistance Semimetal MoAs $_{2}$

R. Lou, Y. F. Xu, L. -X. Zhao +14

While recent advances in band theory and sample growth have expanded the series of extremely large magnetoresistance (XMR) semimetals in transition metal dipnictides $T m P n_{2}$ ( $T m$ …

Experimental evidence of large-gap two-dimensional topological insulator on the surface of ZrTe5

R. Wu, J. -Z. Ma, L. -X. Zhao +12

Two-dimensional (2D) topological insulators (TIs) with a large bulk band-gap are promising for experimental studies of the quantum spin Hall effect and for spintronic device applic…

cond-mat.supr-con2006

Unusual photoemission resonances of oxygen-dopant induced states in Bi $_{2}$ Sr $_{2}$ CaCu $_{2}$ O $_{8 + x}$

P. Richard, Z. -H. Pan, M. Neupane +7

We have performed an angular-resolved photoemission study of underdoped, optimally doped and overdoped Bi $_{2}$ Sr $_{2}$ CaCu $_{2}$ O $_{8 + x}$ samples using a wide photon energy range (15…

Experimental Discovery of the First Nonsymmorphic Topological Insulator KHgSb

J. -Z. Ma, C. -J. Yi, B. Q. Lv +11

Topological insulators (TIs) host novel states of quantum matter, distinguished from trivial insulators by the presence of nontrivial conducting boundary states connecting the vale…

Raman scattering investigation of quasi-one-dimensional superconductor Ta $_{4}$ Pd $_{3}$ Te $_{16}$

D. Chen, P. Richard, Z. -D. Song +6

We have performed polarized Raman scattering measurements on the newly discovered superconductor Ta $_{4}$ Pd $_{3}$ Te $_{16}$ ( $T_{c} = 4.6$ K). We observe twenty-eight out of thirty-th…

Angle-Resolved Photoemission Spectroscopy of Iron-Chalcogenide Superconductor Fe1.03Te0.7Se0.3 : Strong-Coupling Superconductivity and Universality of Inter-Band Scattering

K. Nakayama, T. Sato, P. Richard +8

We have performed high-resolution angle-resolved photoemission spectroscopy of iron-chalcogenide superconductor Fe1.03Te0.7Se0.3 (Tc = 13 K) to investigate the electronic structure…

cond-mat.supr-con2018

Van Hove singularities, chemical pressure and phonons: an angle-resolved photoemission study of KFe $_{2}$ As $_{2}$ and CsFe $_{2}$ As $_{2}$

P. Richard, A. van Roekeghem, X. Shi +6

We report an angle-resolved photoemission spectroscopy (ARPES) study of KFe $_{2}$ As $_{2}$ and CsFe $_{2}$ As $_{2}$ , revealing the existence of a van Hove singularity affecting the electronic…

cond-mat.mtrl-sci2014

Inelastic electron tunneling spectroscopy of nanoporous gold films

H. W. Liu, R. Nishitani, T. Fujita +8

We investigated the localized electronic properties of nanoporous gold films by using an ultra-high vacuum scanning tunneling microscope at low temperature (4.2 K). Second derivati…

Raman scattering investigation of large positive magnetoresistance material WTe $_{2}$

W. -D. Kong, S. -F. Wu, P. Richard +5

We have performed polarized Raman scattering measurements on WTe $_{2}$ , for which an extremely large positive magnetoresistance has been reported recently. We observe 5 A $_{1}$ phonon…

Enhanced superconductivity accompanying a Lifshitz transition in electron-doped FeSe monolayer

X. Shi, Z. -Q. Han, X. -L. Peng +8

The origin of enhanced superconductivity over 50 K in the recently discovered FeSe monolayer films grown on SrTiO $_{3}$ (STO), as compared to 8 K in bulk FeSe, is intensely debated…

cond-mat.str-el2008

Evolution of Fermi surface and normal-state gap in chemically substituted cuprates Bi $_{2}$ Sr $_{2 - x}$ Bi $_{x}$ CuO $_{6 + I^´}$

Z. -H. Pan, P. Richard, Y. -M. Xu +8

We have performed a systematic angle-resolved photoemission study of chemically substituted cuprates Bi $_{2}$ Sr $_{2 - x}$ Bi $_{x}$ CuO $_{6 + I^´}$ . We observed that the Fermi surface area…

cond-mat.str-el2008

Coexistence of competing orders with two energy gaps in real and momentum space in high-Tc superconductor Bi2Sr2-xLaxCuO6+delta

J. -H. Ma, Z. -H. Pan, F. C. Niestemski +12

The superconducting phase of the high-Tc cuprates has been thought to be described by a single d-wave pairing order parameter. Recently, there has been growing evidence suggesting…

Evidence of topological insulator state in the semimetal LaBi

R. Lou, B. -B. Fu, Q. N. Xu +17

By employing angle-resolved photoemission spectroscopy combined with first-principles calculations, we performed a systematic investigation on the electronic structure of LaBi, whi…

Observation of Raman active phonon with Fano lineshape in quasi-one-dimensional superconductor K $_{2}$ Cr $_{3}$ As $_{3}$

W. -L. Zhang, H. Li, Dai Xia +6

We performed a polarized Raman scattering study of quasi-one-dimensional superconductor K $_{2}$ Cr $_{3}$ As $_{3}$ . We detect two A $_{1}^{'}$ phonons and three E $^{'}$ phonons. One of t…

cond-mat.str-el2016

Orbital-differentiated coherence-incoherence crossover identified by photoemission spectroscopy in LiFeAs

H. Miao, Z. P. Yin, S. F. Wu +12

In the iron-based superconductors (FeSCs), orbital differentiation is an important phenomenon, whereby correlations stronger on the dxy orbital than on the dxz/yz orbital yield qua…

Structural phase transition induced by van Hove singularity in 5d transition metal compound IrTe2

T. Qian, H. Miao, Z. J. Wang +17

Comprehensive studies of the electronic states of Ir 5d and Te 5p have been performed to elucidate the origin of the structural phase transition in IrTe2 by combining angle-resolve…

Angle-resolved spectroscopy study of Ni-based superconductor SrNi $_{2}$ As $_{2}$

L. -K. Zeng, P. Richard, A. van Roekeghem +7

We performed an angle-resolved photoemission spectroscopy study of the Ni-based superconductor SrNi $_{2}$ As $_{2}$ . Electron and hole Fermi surface pockets are observed, but their diffe…

Observation of Fermi arc spin texture in TaAs

B. Q. Lv, S. Muff, T. Qian +15

We have investigated the spin texture of surface Fermi arcs in the recently discovered Weyl semimetal TaAs using spin- and angle-resolved photoemission spectroscopy. The experiment…

Fe-based superconductors: an angle-resolved photoemission spectroscopy perspective

P. Richard, T. Sato, K. Nakayama +2

Angle-resolved photoemission spectroscopy allows direct visualization and experimental determination of the electronic structure of crystals in the momentum space, including the pr…

Observation of Dirac Cone Electronic Dispersion in BaFe2As2

P. Richard, K. Nakayama, T. Sato +8

We performed an angle-resolved photoemission spectroscopy study of BaFe2As2, which is the parent compound of the so-called 122 phase of the iron-pnictide high-temperature supercond…

Electronic structure of heavily electron-doped BaFe $_{1.7}$ Co $_{0.3}$ As $_{2}$ studied by angle-resolved photoemission

Y. Sekiba, T. Sato, K. Nakayama +9

We have performed high-resolution angle-resolved photoemission spectroscopy on heavily electron-doped non-superconducting (SC) BaFe $_{1.7}$ Co $_{0.3}$ As $_{2}$ . We find that the two ho…

Superconductivity and electronic fluctuations in Ba $_{1 - x}$ K $_{x}$ Fe $_{2}$ As $_{2}$ studied by Raman scattering

S. -F. Wu, P. Richard, H. Ding +6

Using polarization-resolved electronic Raman scattering we study under-doped, optimally-doped and over-doped Ba $_{1 - x}$ K $_{x}$ Fe $_{2}$ As $_{2}$ samples in the normal and superconducting…

Band Structure and Fermi Surface of an Extremely Overdoped Iron-Based Superconductor KFe2As2

T. Sato, K. Nakayama, Y. Sekiba +8

We have performed high-resolution angle-resolved photoemission spectroscopy on heavily overdoped KFe_2As_2 (transition temperature (Tc = 3 K). We observed several renormalized band…

On the origin of the electronic anisotropy in iron pnicitde superconductors

W. -L. Zhang, P. Richard, H. Ding +5

We use polarization-resolved Raman spectroscopy to study the anisotropy of the electronic characteristics of the iron-pnictide parent compounds $A$ Fe $_{2}$ As $_{2}$ ( $A$ ~=~Eu, Sr).…

Emergence of topological bands on the surface of ZrSnTe crystal

R. Lou, J. -Z. Ma, Q. -N. Xu +12

By using angle-resolved photoemission spectroscopy combined with first-principles calculations, we reveal that the topmost unit cell of ZrSnTe crystal hosts two-dimensional (2D) el…

ARPES measurements of the superconducting gap of Fe-based superconductors and their implications to the pairing mechanism

P. Richard, T. Qian, H. Ding

Its direct momentum sensitivity confers to angle-resolved photoemission spectroscopy (ARPES) a unique perspective in investigating the superconducting gap of multi-band systems. In…

cond-mat.supr-con2007

Antiferromagnetism-superconductivity competition in electron-doped cuprates triggered by oxygen reduction

P. Richard, M. Neupane, Y. -M. Xu +5

We have performed a systematic angle-resolved photoemission study of as-grown and oxygen-reduced Pr $_{2 - x}$ Ce $_{x}$ CuO $_{4}$ and Pr $_{1 - x}$ LaCe $_{x}$ CuO $_{4}$ electron-doped cuprates. In…

Topological nature of FeSe $_{0.5}$ Te $_{0.5}$ superconductor

Zhijun Wang, P. Zhang, Gang Xu +10

We demonstrate, using first-principles calculations, that the electronic structure of FeSe $_{1 - x}$ Te $_{x}$ ( $x$ =0.5) is topologically non-trivial, characterized by an odd $\mathbb…

Three-component fermions with surface Fermi arcs in topological semimetal tungsten carbide

J. -Z. Ma, J. -B. He, Y. -F. Xu +19

Topological Dirac and Weyl semimetals not only host quasiparticles analogous to the elementary fermionic particles in high-energy physics, but also have nontrivial band topology ma…

Raman scattering investigation of superconducting Ba $_{2}$ Ti $_{2}$ Fe $_{2}$ As $_{4}$ O

S. -F. Wu, P. Richard, W. -L. Zhang +5

We have performed polarized Raman scattering measurements on the newly discovered superconductor Ba $_{2}$ Ti $_{2}$ Fe $_{2}$ As $_{4}$ O $_{2}$ ( $T_{c} = 21$ K). We observe seven out of eig…

Collective excitations of dynamic Fermi surface deformations in BaFe $_{2}$ (As $_{0.5}$ P $_{0.5}$ ) $_{2}$

S. -F. Wu, W. -L. Zhang, D. Hu +7

We use electronic Raman scattering to study the low-energy excitations in BaFe $_{2}$ (As $_{0.5}$ P $_{0.5}$ ) $_{2}$ ( $T_{c} \approx 16$ K) samples. In addition to a superconducting pair brea…

Spin-Fluctuation-Induced Non-Fermi-Liquid Behavior with suppressed superconductivity in LiFe $_{1 - x}$ Co $_{x}$ As

Y. M. Dai, H. Miao, L. Y. Xing +12

A series of LiFe $_{1 - x}$ Co $_{x}$ As compounds with different Co concentrations have been studied by transport, optical spectroscopy, angle-resolved photoemission spectroscopy and nu…

Observation of high-Tc superconductivity in rectangular FeSe/STO(110) monolayer

P. Zhang, X. -L. Peng, T. Qian +12

It is well known that superconductivity in Fe-based materials is favoured under tetragonal symmetry, whereas competing orders such as spin-density-wave (SDW) and nematic orders eme…

Observation of non-Fermi liquid behavior in hole-doped LiFe $_{1 - x}$ V $_{x}$ As

L. Y. Xing, X. Shi, P. Richard +12

We synthesized a series of V-doped LiFe $_{1 - x}$ V $_{x}$ As single crystals. The superconducting transition temperature $T_{c}$ of LiFeAs decreases rapidly at a rate of 7 K per 1\% V. The…

Universality of superconducting gaps in overdoped Ba0.3K0.7Fe2As2 observed by angle-resolved photoemission spectroscopy

K. Nakayama, T. Sato, P. Richard +8

We have performed angle-resolved photoemission spectroscopy on the overdoped Ba $_{0.3}$ K $_{0.7}$ Fe $_{2}$ As $_{2}$ superconductor ( $T_{c}$ = 22 K). We demonstrate that the superconducting…

cond-mat.supr-con2003

Fourfold oscillations and anomalous magnetic irreversibility of magnetoresistance in the non-metallic regime of Pr1.85Ce0.15CuO4

P. Fournier, M. -E. Gosselin, S. Savard +4

Using magnetoresistance measurements as a function of applied magnetic field and its direction of application, we present sharp angular-dependent magnetoresistance oscillations for…

Disentangling the surface and bulk electronic structures of LaOFeAs

P. Zhang, J. Ma, T. Qian +7

We performed a comprehensive angle-resolved photoemission spectroscopy study of the electronic band structure of LaOFeAs single crystals. We found that samples cleaved at low tempe…

Magneto-elastic coupling in Fe-based superconductors

S. -F. Wu, W. -L. Zhang, V. K. ThorsmÃ¸lle +12

We used polarization-resolved Raman scattering to study the magneto-elastic coupling in the parent compounds of several families of Fe-based superconductors (BaFe2As2, EuFe2As2, Na…

On the origin of critical nematic fluctuations in pnictide superconductors

S. -F. Wu, W. -L. Zhang, L. Li +6

We employ polarization-resolved Raman spectroscopy to study critical nematic fluctuations in Ba(Fe $_{1 - x}$ Au $_{x}$ ) $_{2}$ As $_{2}$ superconductors above and across well separated tetragon…

Strong nodeless pairing on separate electron Fermi surface sheets in (Tl, K)Fe $_{1.78}$ Se $_{2}$ probed by ARPES

X. -P. Wang, T. Qian, P. Richard +6

We performed a high-resolution angle-resolved photoemission spectroscopy study of the Tl $_{0.63}$ K $_{0.37}$ Fe $_{1.78}$ Se $_{2}$ superconductor ( $T_{c} = 29$ K). We show the existence of t…

Comparative Raman study of Weyl semimetals TaAs, NbAs, TaP and NbP

H. W. Liu, P. Richard, L. X. Zhao +2

We report a comparative polarized Raman study of Weyl semimetals TaAs, NbAs, TaP and NbP. The evolution of the phonon frequencies with the sample composition allows us to determine…

Isotropic superconducting gaps with enhanced pairing on electron Fermi surfaces in FeTe0.55Se0.45

H. Miao, P. Richard, Y. Tanaka +17

The momentum distribution of the energy gap opening at the Fermi level of superconductors is a direct fingerprint of the pairing mechanism. While the phase diagram of the iron-base…

Unconventional superconducting gap in NaFe $_{0.95}$ Co $_{0.05}$ As observed by angle-resolved photoemission spectroscopy

Z. -H. Liu, P. Richard, K. Nakayama +16

We have performed high resolution angle-resolved photoemission measurements on superconducting electron-doped NaFe $_{0.95}$ Co $_{0.05}$ As ( $T_{c} \sim$ 18 K). We observed a hole-like…

cond-mat.mes-hall2016

Compensated semimetal LaSb with unsaturated magnetoresistance

L. -K. Zeng, R. Lou, D. -S. Wu +23

By combining angle-resolved photoemission spectroscopy and quantum oscillation measurements, we performed a comprehensive investigation on the electronic structure of LaSb, which e…

Three-dimensionality and orbital characters of Fermi surface in (Tl,Rb) $_{y}$ Fe $_{2 - x}$ Se $_{2}$

Z. -H. Liu, P. Richard, N. Xu +11

We report a comprehensive angle-resolved photoemission spectroscopy study of the tridimensional electronic bands in the recently discovered Fe selenide superconductor (Tl,Rb) $_{y}$ Fe…

Superconducting gap symmetry of Ba0.6K0.4Fe2As2 studied by angle-resolved photoemission spectroscopy

K. Nakayama, T. Sato, P. Richard +8

We have performed high-resolution angle-resolved photoemission spectroscopy on the optimally-doped Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ compound and determined the accurate momentum dep…

Experimental discovery of Weyl semimetal TaAs

B. Q. Lv, H. M. Weng, B. B. Fu +11

Weyl semimetals are a class of materials that can be regarded as three-dimensional analogs of graphene breaking time reversal or inversion symmetry. Electrons in a Weyl semimetal b…

Observation of anomalous temperature dependence of spectrum on small Fermi surfaces in a BiS2-based superconductor

L. K. Zeng, X. B. Wang, J. Ma +7

We performed an angle-resolved photoemission spectroscopy study of the BiS2-based superconductor Nd(O,F)BiS2. Two small electron-like Fermi surfaces around X (pi, 0) are observed,…

Is BaCr $_{2}$ As $_{2}$ symmetrical to BaFe $_{2}$ As $_{2}$ with respect to half $3 d$ shell filling?

P. Richard, A. van Roekeghem, B. Q. Lv +7

We have performed an angle-resolved photoemission spectroscopy study of BaCr $_{2}$ As $_{2}$ , which has the same crystal structure as BaFe $_{2}$ As $_{2}$ , a parent compound of Fe-based superc…

Raman study of lattice dynamics in Weyl semimetal TaAs

H. W. Liu, P. Richard, Z. D. Song +4

We report a polarized Raman study of Weyl semimetal TaAs. We observe all the optical phonons, with energies and symmetries consistent with our first-principles calculations. We det…

Observation of momentum-confined in-gap impurity state in Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ : evidence for anti-phase $s_{\pm}$ pairing

P. Zhang, P. Richard, T. Qian +12

We report the observation by angle-resolved photoemission spectroscopy of an impurity state located inside the superconducting gap of Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ and vanishing…

Commensurate lattice distortion in the layered titanium oxypnictides Na $_{2}$ Ti $_{2} P n_{2}$ O ( $P n =$ As, Sb) determined by X-ray diffraction

N. R. Davies, R. D. Johnson, A. J. Princep +12

We report single crystal X-ray diffraction measurements on Na $_{2}$ Ti $_{2} P n_{2}$ O ( $P n$ = As, Sb) which reveal a charge superstructure that appears below the density wave transition…

Direct spectroscopic evidence for completely filled Cu $3 d$ shell in BaCu $_{2}$ As $_{2}$ and $I^\pm$ -BaCu $_{2}$ Sb $_{2}$

S. F. Wu, P. Richard, A. van Roekeghem +9

We use angle-resolved photoemission spectroscopy to extract the band dispersion and the Fermi surface of BaCu $_{2}$ As $_{2}$ and $I^\pm$ -BaCu $_{2}$ Sb $_{2}$ . While the Cu $3 d$ bands in both mat…

Angle-resolved photoemission spectroscopy observation of anomalous electronic states in EuFe $_{2}$ As $_{2 - x}$ P $_{x}$

P. Richard, C. Capan, J. Ma +8

We used angle-resolved photoemission spectroscopy to investigate the electronic structure of EuFe $_{2}$ As $_{2}$ , EuFe $_{2}$ As $_{1.4}$ P $_{0.6}$ and EuFe $_{2}$ P $_{2}$ . We observed doubled core…

Possible nodal superconducting gap emerging at the Lifshitz transition in heavily hole-doped Ba0.1K0.9Fe2As2

N. Xu, P. Richard, X. Shi +11

We performed a high energy resolution ARPES investigation of over-doped Ba0.1K0.9Fe2As2 with T_c= 9 K. The Fermi surface topology of this material is similar to that of KFe2As2 and…

cond-mat.soft2014

Slow relaxation and aging phenomena at nano-scale in granular materials

V. Y. Zaitsev, V. E. Gusev, V. Tournat +1

Complex systems having metastable elements often demonstrate nearly log-time relaxations and a kind of aging: repeated stimuli weaken the system's relaxational response. Granular m…

Observation of an isotropic superconducting gap at the Brillouin zone center of Tl $_{0.63}$ K $_{0.37}$ Fe $_{1.78}$ Se $_{2}$

X. -P. Wang, P. Richard, A. van Roekeghem +10

We performed a high-resolution angle-resolved photoemission spectroscopy study on superconducting (SC) Tl $_{0.63}$ K $_{0.37}$ Fe $_{1.78}$ Se $_{2}$ ( $T_{c} = 29$ K) in the whole Brillouin zo…

cond-mat.str-el2012

Electronic band structure of BaCo $_{2}$ As $_{2}$ : a fully-doped ferropnictide with reduced electronic correlations

N. Xu, P. Richard, A. van Roekeghem +8

We report an angle-resolved photoemission spectroscopy investigation of the Fermi surface and electronic band structure of BaCo $_{2}$ As $_{2}$ . Although its quasi-nesting-free Fermi s…

Raman study of electron-phonon coupling in thin films of LiTi $_{2}$ O $_{4}$ spinel oxide superconductor

D. Chen, Y. -L. Jia, T. -T. Zhang +4

We performed a Raman scattering study of thin films of LiTi $_{2}$ O $_{4}$ spinel oxide superconductor. We detected four out of five Raman active modes, with frequencies in good accordan…

ARPES observation of isotropic superconducting gaps in isovalent Ru-substituted Ba(Fe $_{0.75}$ Ru $_{0.25}$ ) $_{2}$ As $_{2}$

N. Xu, P. Richard, X. -P. Wang +13

We used high-energy resolution angle-resolved photoemission spectroscopy to extract the momentum dependence of the superconducting gap of Ru-substituted Ba(Fe $_{0.75}$ Ru $_{0.25}$ )$…

cond-mat.supr-con2010

Absence of holelike Fermi surface in superconducting K0.8Fe1.7Se2 revealed by ARPES

T. Qian, X. -P. Wang, W. -C. Jin +8

We have performed an angle-resolved photoemission spectroscopy study of the new iron-based superconductor K0.8Fe1.7Se2 (Tc ~ 30 K). Clear band dispersion is observed with the overa…

cond-mat.str-el2008

Observation of a novel orbital selective Mott transition in Ca $_{1.8}$ Sr $_{0.2}$ RuO $_{4}$

M. Neupane, P. Richard, Z. -H. Pan +7

Electrons in a simple correlated system behave either as itinerant charge carriers or as localized moments. However, there is growing evidence for the coexistence of itinerant elec…

Fermi surface dichotomy of the superconducting gap and pseudogap in underdoped pnictides

Y. -M. Xu, P. Richard, K. Nakayama +15

High-temperature superconductivity in iron-arsenic materials (pnictides) near an antiferromagnetic phase raises the possibility of spin-fluctuation-mediated pairing. However, the i…

cond-mat.supr-con2006

Universal quasiparticle decoherence in hole- and electron-doped high-Tc cuprates

Z. -H. Pan, P. Richard, A. V. Fedorov +8

We use angle-resolved photoemission to unravel the quasiparticle decoherence process in the high- $T_{c}$ cuprates. The coherent band is highly renormalized, and the incoherent part m…

Experimental investigation of the electronic structure of Ca $_{0.83}$ La $_{0.17}$ Fe $_{2}$ As $_{2}$

Y. -B. Huang, P. Richard, J. -H. Wang +12

We performed a combined angle-resolved photoemission spectroscopy and scanning tunneling microscopy study of the electronic structure of electron-doped Ca $_{0.83}$ La $_{0.17}$ Fe $_{2}$ …

Effects of Ru Substitution on Dimensionality and Electron Correlations in Ba(Fe_{1-x}Ru_x)_2As_2

N. Xu, T. Qian, P. Richard +12

We report a systematic angle-resolved photoemission spectroscopy study on Ba(Fe $_{1 - x}$ Ru $_{x}$ ) $_{2}$ As $_{2}$ for a wide range of Ru concentrations (0.15 $\leq$ \emph{x} $\leq$ 0.74). W…

Anomalous magneto-elastic coupling in Au-doped BaFe2As2

S. -F. Wu, W. -L. Zhang, L. Li +6

We used polarization-resolved Raman scattering to study magneto-elastic coupling in Ba(Fe $_{1 - x}$ Au $_{x}$ ) $_{2}$ As $_{2}$ crystals as a function of light Au-doping, materials for which…

Observation of strong electron pairing on bands without Fermi surfaces in LiFe1-xCoxAs

H. Miao, T. Qian, X. Shi +8

In conventional BCS superconductors, the quantum condensation of superconducting electron pairs is understood as a Fermi surface (FS) instability, in which the low-energy electrons…

Observation of an Orbital Selective Electron-Mode Coupling in Fe-Based High- $T_{c}$ Superconductors

P. Richard, T. Sato, K. Nakayama +7

We have performed an angle-resolved photoemission spectroscopy study of the new superconductor Ba $_{0.6}$ K $_{0.4}$ Fe $_{2}$ As $_{2}$ in the low energy range. We report the observation of…

cond-mat.mtrl-sci2018

Observation of a nodal chain with Dirac surface states in TiB2

C. -J. Yi, B. Q. Lv, Q. S. Wu +13

Topological nodal-line semimetals (TNLSMs) are characterized by symmetry-protected band crossings extending along one-dimensional lines in momentum space. The nodal lines exhibit a…

New phase transition in Na $_{2}$ Ti $_{2}$ As $_{2}$ O revealed by Raman scattering

D. Chen, T. T. Zhang, Z. -D. Song +8

We performed a Raman scattering study of Na $_{2}$ Ti $_{2}$ As $_{2}$ O. We identified a symmetry breaking structural transition at around $T_{s} = 150$ K, which matches a large bump in the ele…

ARPES observation of Mn-pnictide hybridization and negligible band structure renormalization in BaMn $_{2}$ As $_{2}$ and BaMn $_{2}$ Sb $_{2}$

W. -L. Zhang, P. Richard, A. van Roekeghem +14

We performed an angle-resolved photoemission spectroscopy study of BaMn $_{2}$ As $_{2}$ and BaMn $_{2}$ Sb $_{2}$ , which are isostructural to the parent compound BaFe $_{2}$ As $_{2}$ of the 122 famil…

Coexistence of orbital degeneracy lifting and superconductivity in iron-based superconductors

H. Miao, L. -M. Wang, P. Richard +10

In contrast to conventional superconducting (SC) materials, superconductivity in high-temperature superconductors (HTCs) usually emerges in the presence of other fluctuating orders…

Unconventional Anisotropic s-Wave Superconducting Gaps of LiFeAs Iron-Pnictide Superconductor

K. Umezawa, Y. Li, H. Miao +10

We have performed high-resolution angle-resolved photoemission spectroscopy on Fe-based superconductor LiFeAs (Tc = 18 K). We reveal multiple nodeless superconducting (SC) gaps wit…

Evolution of a pairing-induced pseudogap from the superconducting gap of (Bi,Pb)2Sr2CuO6

K. Nakayama, T. Sato, Y. Sekiba +7

We have performed an ultrahigh-resolution angle-resolved photoemission spectroscopy study of slightly-overdoped (Bi,Pb)2Sr2CuO6 to elucidate the origin of pseudogap. By using a new…