Publications (87)
Large linear magnetoresistance in the Dirac semimetal TlBiSSe
Mario Novak, Satoshi Sasaki, Kouji Segawa +1
The mixed-chalcogenide compound TlBiSSe realizes a three-dimensional (3D) Dirac semimetal state. In clean, low-carrier-density single crystals of this material, we found Shubnikov-…
Magnetoresistance of Untwinned YBa_{2}Cu_{3}O_{y} Single Crystals in a Wide Range of Doping: Anomalous Hole-Doping Dependence of the Coherence Length
Yoichi Ando, Kouji Segawa
Magnetoresistance (MR) in the a-axis resistivity of untwinned YBa_{2}Cu_{3}O_{y} single crystals is measured for a wide range of doping (y = 6.45 - 7.0). The y-dependence of the in…
Thermodynamic and transport properties of underdoped cuprates from ARPES data
T. Yoshida, X. J. Zhou, H. Yagi +11
he relationship between photoemission spectra of high- cuprates and their thermodynamic and transport properties are discussed. The doping dependence of the expecte…
Constant effective mass across the phase diagram of high-T cuprates
W. J. Padilla, Y. S. Lee, M. Dumm +6
We investigate the hole dynamics in two prototypical high temperature superconducting systems: LaSrCuO and YBaCuO using a combination of DC…
Observations of two-dimensional quantum oscillations and ambipolar transport in the topological insulator Bi2Se3 achieved by Cd doping
Zhi Ren, A. A. Taskin, Satoshi Sasaki +2
We present a defect-engineering strategy to optimize the transport properties of the topological insulator Bi2Se3 to show a high bulk resistivity and clear quantum oscillations. St…
Additional Evidence for the Surface Origin of the Peculiar Angular-Dependent Magnetoresistance Oscillations Discovered in a Topological Insulator Bi_{1-x}Sb_{x}
A. A. Taskin, Kouji Segawa, Yoichi Ando
We present detailed data on the unusual angular-dependent magnetoresistance oscillation phenomenon recently discovered in a topological insulator Bi_{0.91}Sb_{0.09}. Direct compari…
Odd-Parity Pairing and Topological Superconductivity in a Strongly Spin-Orbit Coupled Semiconductor
Satoshi Sasaki, Zhi Ren, A. A. Taskin +3
The existence of topological superconductors preserving time-reversal symmetry was recently predicted, and they are expected to provide a solid-state realization of itinerant massl…
Magnetotransport study of the charged stripes in high-T_c cuprates
Yoichi Ando, A. N. Lavrov, Kouji Segawa
We present a study of the in-plane and out-of-plane magnetoresistance (MR) in heavily-underdoped, antiferromagnetic YBa_{2}Cu_{3}O_{6+x}, which reveals a variety of striking featur…
Electronic Phase Diagram of High-T_c Cuprate Superconductors from a Mapping of the In-Plane Resistivity Curvature
Yoichi Ando, Seiki Komiya, Kouji Segawa +2
We propose that Resistivity Curvature Mapping (RCM) based on the in-plane resistivity data is a useful way to objectively draw an electronic phase diagrams of high-T_c cuprates, wh…
Large bulk resistivity and surface quantum oscillations in the topological insulator Bi2Te2Se
Zhi Ren, A. A. Taskin, Satoshi Sasaki +2
Topological insulators are predicted to present novel surface transport phenomena, but their experimental studies have been hindered by a metallic bulk conduction that overwhelms t…
Bulk superconducting phase with a full energy gap in the doped topological insulator Cu_xBi_2Se_3
M. Kriener, Kouji Segawa, Zhi Ren +2
The superconductivity recently found in the doped topological insulator Cu_xBi_2Se_3 offers a great opportunity to search for a topological superconductor. We have successfully pre…
Disparities in the Josephson vortex state electrodynamics of high-Tc cuprates
A. D. LaForge, W. J. Padilla, K. S. Burch +5
We report on far infrared measurements of interplane conductivity for underdoped single-crystal YBa2Cu3Oy in magnetic field and situate these new data within earlier work on two ot…
Strong-coupling Effects in cuprate High- Superconductors by magnetooptical studies
Y. S. Lee, Z. Q. Li, W. J. Padilla +5
Signatures of strong coupling effects in cuprate high- superconductors have been authenticated through a variety of spectroscopic probes. However, the microscopic nature of…
Transport Anomalies and the Role of Pseudogap in the "60-K Phase" of YBa_{2}Cu_{3}O_{7-δ}
Kouji Segawa, Yoichi Ando
We report the result of our accurate measurements of the a- and b-axis resistivity, Hall coefficient, and the a-axis thermopower in untwinned YBa_{2}Cu_{3}O_{y} single crystals in…
Unexpected mass acquisition of Dirac fermions at the quantum phase transition of a topological insulator
T. Sato, Kouji Segawa, K. Kosaka +6
The three-dimensional (3D) topological insulator is a novel quantum state of matter where an insulating bulk hosts a linearly-dispersing surface state, which can be viewed as a sea…
Manipulation of Topological States and Bulk Band Gap Using Natural Heterostructures of a Topological Insulator
K. Nakayama, K. Eto, Y. Tanaka +5
We have performed angle-resolved photoemission spectroscopy on (PbSe)5(Bi2Se3)3m, which forms a natural multilayer heterostructure consisting of a topological insulator (TI) and an…
Anomalous suppression of the superfluid density in the CuxBi2Se3 superconductor upon progressive Cu intercalation
M. Kriener, Kouji Segawa, Satoshi Sasaki +1
CuxBi2Se3 was recently found to be likely the first example of a time-reversal-invariant topological superconductor accompanied by helical Majorana fermions on the surface. Here we…
Coherence and superconductivity in coupled one-dimensional chains: a case study of YBaCuO
Y. S. Lee, Kouji Segawa, Yoichi Ando +1
We report the infrared (IR) response of Cu-O chains in the high- superconductor YBaCuO over the doping range spanning . We find evidence for…
Work function of bulk-insulating topological insulator Bi2-xSbxTe3-ySey
Daichi Takane, Seigo Souma, Takafumi Sato +3
Recent discovery of bulk insulating topological insulator (TI) Bi2-xSbxTe3-ySey paved a pathway toward practical device application of TIs. For realizing TI-based devices, it is ne…
Anomalous metallic state above the upper critical field of the conventional three-dimensional superconductor AgSnSe2 with strong intrinsic disorder
Zhi Ren, M. Kriener, A. A. Taskin +3
We report superconducting properties of AgSnSe2 which is a conventional type-II superconductor in the very dirty limit due to intrinsically strong electron scatterings. While this…
Ando, Lavrov, and Segawa Reply
Yoichi Ando, A. N. Lavrov, Kouji Segawa
Authors' Reply to the Comment by Janossy et al. [cond-mat/0005275] on our article, "Magnetoresistance Anomalies in Antiferromagnetic YBa_{2}Cu_{3}O_{6+x}: Fingerprints of Charged S…
Direct Observation of Nonequivalent Fermi-Arc States of Opposite Surfaces in Noncentrosymmetric Weyl Semimetal NbP
S. Souma, Zhiwei Wang, H. Kotaka +9
We have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) on noncentrosymmetric Weyl semimetal candidate NbP, and determined the electronic states of both…
Pb_{5}Bi_{24}Se_{41}: A New Member of the Homologous Series Forming Topological Insulator Heterostructures
Kouji Segawa, A. A. Taskin, Yoichi Ando
We have synthesized Pb_{5}Bi_{24}Se_{41}, which is a new member of the (PbSe)_{5}(Bi2Se3)_{3m} homologous series with m = 4. This series of compounds consist of alternating layers…
Universal scaling for the spin-electricity conversion on surface states of topological insulators
K. T. Yamamoto, Y. Shiomi, Kouji Segawa +2
We have investigated spin-electricity conversion on surface states of bulk-insulating topological insulator (TI) materials using a spin pumping technique. The sample structure is N…
Unexpectedly robust protection from backscattering in the topological insulator BiSbTeSe
Sunghun Kim, Shunsuke Yoshizawa, Yukiaki Ishida +5
Electron scattering in the topological surface state (TSS) of the bulk-insulating topological insulator BiSbTeSe was studied using quasiparticle int…
Specific-heat evidence for strong electron correlations in the thermoelectric material (Na,Ca)Co_{2}O_{4}
Yoichi Ando, N. Miyamoto, Kouji Segawa +2
The specific heat of (Na,Ca)Co_{2}O_{4} is measured at low-temperatures to determine the magnitude of the electronic specific-heat coefficient γ, in an attempt to gain an insight…
Magnetoresistance Anomalies in Antiferromagnetic YBa_2Cu_3O_{6+x}: Fingerprints of Charged Stripes
Yoichi Ando, A. N. Lavrov, Kouji Segawa
We report novel features in the in-plane magnetoresistance (MR) of heavily underdoped YBa_2Cu_3O_{6+x}, which unveil a developed ``charged stripe'' structure in this system. One of…
Quasiparticle dynamics and in-plane anisotropy in system near onset of superconductivity
Y. -S. Lee, Kouji Segawa, Yoichi Ando +1
We report on an infrared study of carrier dynamics within the CuO planes in heavily underdoped detwinned single crystals of YBaCuO. In an effort to reveal…
Magnetotransport properties of untwinned YBa_{2}Cu_{3}O_{y} single crystals: Novel 60-K-phase anomalies in the charge transport
Yoichi Ando, Kouji Segawa
We present the result of our accurate measurements of the a- and b-axis resistivity (Ï_a and Ï_b), magnetoconductivity (ÎÏ/ Ï), Hall coefficient R_H, and the a-axis thermopowe…
Spin-Orbit Coupling and Anomalous Angular-Dependent Magnetoresistance in the Quantum Transport Regime of PbS
Kazuma Eto, A. A. Taskin, Kouji Segawa +1
We measured magnetotransport properties of PbS single crystals which exhibit the quantum linear magnetoresistance (MR) as well as the static skin effect that creates a surface laye…
Topological Surface Transport in Epitaxial SnTe Thin Films Grown on Bi2Te3
A. A. Taskin, Fan Yang, Satoshi Sasaki +2
The topological crystalline insulator SnTe has been grown epitaxially on a Bi2Te3 buffer layer by molecular beam epitaxy. In a 30-nm-thick SnTe film, p- and n-type carriers are fou…
Direct Observation of the Topological Surface States in Lead-Based Ternary Telluride Pb(Bi1-xSbx)2Te4
S. Souma, K. Eto, M. Nomura +5
We have performed angle-resolved photoemission spectroscopy on Pb(Bi1-xSbx)2Te4, which is a member of lead-based ternary tellurides and has been theoretically proposed as a candida…
Top gating of epitaxial (Bi_{1-x}Sb_x)2Te3 topological insulator thin films
Fan Yang, A. A. Taskin, Satoshi Sasaki +4
The tunability of the chemical potential for a wide range encompassing the Dirac point is important for many future devices based on topological insulators. Here we report a method…
Evolution of the Hall Coefficient and the Peculiar Electronic Structure of the Cuprate Superconductors
Yoichi Ando, Y. Kurita, Seiki Komiya +2
Although the Hall coefficient R_H is an informative transport property of metals and semiconductors, its meaning in the cuprate superconductors has been ambiguous because of its un…
Electrical Resistivity Anisotropy from Self-Organized One-Dimensionality in High-Temperature Superconductors
Yoichi Ando, Kouji Segawa, Seiki Komiya +1
We investigate the manifestation of the stripes in the in-plane resistivity anisotropy in untwinned single crystals of La_{2-x}Sr_{x}CuO_{4} (x = 0.02 - 0.04) and YBa_{2}Cu_{3}O_{y…
Ferromagnetism in Cr-doped topological insulator TlSbTe2
Zhiwei Wang, Kouji Segawa, Satoshi Sasaki +2
We have synthesized a new ferromagnetic topological insulator by doping Cr to the ternary topological-insulator material TlSbTe2. Single crystals of Tl_{1-x}Cr_{x}SbTe2 were grown…
Observation of Two-Dimensional Bulk Electronic States in a Superconducting Topological Insulator Heterostructure Cux(PbSe)5(Bi2Se3)6: Implications for Unconventional Superconductivity
K. Nakayama, H. Kimizuka, Y. Tanaka +6
We have performed angle-resolved photoemission spectroscopy (ARPES) on Cux(PbSe)5(Bi2Se3)6 (CPSBS; x = 1.47), a superconductor derived from a topological insulator heterostructure,…
Anomalous dressing of Dirac fermions in the topological surface state of Bi2Se3, Bi2Te3, and CuxBi2Se3
Takeshi Kondo, Y. Nakashima, Y. Ota +8
Quasiparticle dynamics on the topological surface state of Bi2Se3, Bi2Te3, and superconducting CuxBi2Se3 are studied by 7 eV laser-based angle resolved photoemission spectroscopy.…
Manifestations of the Charged Stripes in the Magnetoresistance of Heavily Underdoped YBa_2Cu_3O_{6+x}
A. N. Lavrov, Yoichi Ando, Kouji Segawa
We present a study of the in-plane and out-of-plane magnetoresistance (MR) in heavily-underdoped, antiferromagnetic YBa_2Cu_3O_{6+x}, which reveals a variety of striking features.…
Charge Transport Properties of Lightly-Doped Cuprates: Behavior of the Hall Coefficient
Yoichi Ando, Kouji Segawa, A. N. Lavrov +1
Behavior of Ï_{ab}(T) and R_{H}(T) is presented for LSCO and YBCO single crystals in the lightly hole-doped antiferromagnetic region, with an emphasis on the R_{H}(T) data. In bot…
Nano-mosaic of Topological Dirac States on the Surface of Pb5Bi24Se41 Observed by Nano-ARPES
Kosuke Nakayama, Seigo Souma, Chi Xuan Trang +9
We have performed scanning angle-resolved photoemission spectroscopy with a nanometer-sized beam spot (nano-ARPES) on the cleaved surface of Pb5Bi24Se41, which is a member of the (…
Switching of Charge-Current-Induced Spin Polarization in the Topological Insulator BiSbTeSe2
Fan Yang, Subhamoy Ghatak, A. A. Taskin +7
The charge-current-induced spin polarization is a key property of topological insulators for their applications in spintronics. However, topological surface states are expected to…
Robust topological surface states in skyrmion-host magnets Eu(Ga,Al)4: evidence for dual topology
Yuki Arai, Kosuke Nakayama, Takemi Kato +10
The interplay between real-space topology such as magnetic skyrmions and momentum-space topology characterized by topological surface states (TSSs) is predicted to realize novel ph…
A new superconductor derived from topological insulator heterostructure
Satoshi Sasaki, Kouji Segawa, Yoichi Ando
Topological superconductors (TSCs) are of significant current interest because they offer promising platforms for finding Majorana fermions. Here we report a new superconductor syn…
Bulk topological insulators as inborn spintronics detectors
Y. Shiomi, K. Nomura, Y. Kajiwara +5
Detection and manipulation of electrons' spins are key prerequisites for spin-based electronics or spintronics. This is usually achieved by contacting ferromagnets with metals or s…
Observation of Dirac Holes and Electrons in a Topological Insulator
A. A. Taskin, Zhi Ren, Satoshi Sasaki +2
We show that in the new topological-insulator compound Bi_{1.5}Sb_{0.5}Te_{1.7}Se_{1.3} one can achieve a surfaced-dominated transport where the surface channel contributes up to 7…
Charge Localization from Local Destruction of Antiferromagnetic Correlation in Zn-doped YBa2Cu3O7-d
Kouji Segawa, Yoichi Ando
The in-plane normal-state resistivity of Zn-doped YBa2Cu3O7-d single crystals is measured down to low temperatures by suppressing superconductivity with magnetic fields up to 18 T.…
Optimizing the Bi_(2-x)Sb_(x)Te_(3-y)Se_(y) solid solutions to approach the intrinsic topological insulator regime
Zhi Ren, A. A. Taskin, Satoshi Sasaki +2
To optimize the bulk-insulating behavior in the topological insulator materials having the tetradymite structure, we have synthesized and characterized single-crystal samples of Bi…
Topological Superconductivity in CuxBi2Se3
Satoshi Sasaki, M. Kriener, Kouji Segawa +4
A topological superconductor (TSC) is characterized by the topologically-protected gapless surface state that is essentially an Andreev bound state consisting of Majorana fermions.…
Revealing puddles of electrons and holes in compensated topological insulators
N. Borgwardt, J. Lux, I. Vergara +7
Three-dimensional topological insulators harbour metallic surface states with exotic properties. In transport or optics, these properties are typically masked by defect-induced bul…
Two types of Dirac-cone surface states on (111) surface of topological crystalline insulator SnTe
Y. Tanaka, T. Shoman, K. Nakayama +6
We have performed angle-resolved photoemission spectroscopy (ARPES) on the (111) surface of the topological crystalline insulator SnTe. Distinct from a pair of Dirac-cone surface s…
Fermiology of Strongly Spin-Orbit Coupled Superconductor Sn1-xInxTe and its Implication to Topological Superconductivity
T. Sato, Y. Tanaka, K. Nakayama +7
We have performed angle-resolved photoemission spectroscopy of the strongly spin-orbit coupled low-carrier density superconductor Sn1-xInxTe (x = 0.045) to elucidate the electronic…
Metal-to-Insulator Crossover in YBa_{2}Cu_{3}O_{y} Probed by Low-Temperature Quasiparticle Heat Transport
X. F. Sun, Kouji Segawa, Yoichi Ando
It was recently demonstrated that in La_{2-x}Sr_{x}CuO_{4} the magnetic-field (H) dependence of the low-temperature thermal conductivity κup to 16 T reflects whether the normal st…
Unusual Charge Localization in Zn-doped and Heavily Underdoped YBa2Cu3O7-d at Low Temperatures
Kouji Segawa, Yoichi Ando
The in-plane normal-state resistivity of Zn-doped YBa2Cu3O7-d and heavily underdoped pure YBCO single crystals is measured down to low temperatures under magnetic fields up to 18 T…
Pitfalls in the analysis of low-temperature thermal conductivity of high-Tc cuprates
Yoichi Ando, X. F. Sun, Kouji Segawa
Recently, it was proposed that phonons are specularly reflected below about 0.5 K in ordinary single-crystal samples of high-T_c cuprates, and that the low-temperature thermal cond…
Spin-Polarized Quantum Well States on BiFeSe
Michael M. Yee, Z. -H. Zhu, Anjan Soumyanarayanan +8
Low temperature scanning tunneling microscopy is used to image the doped topological insulator BiFeSe. Interstitial Fe defects allow the detection of quasiparticle…
Instantaneous Photon Drag Currents in Topological Insulators
Yoshito Onishi, Zhi Ren, Mario Novak +3
Topological insulator materials have been extensively studied in the field of condensed matter physics because nontrivial topology in the electronic state gives rise to a novel spi…
Low-temperature nodal-quasiparticle transport in lightly doped YBa_{2}Cu_{3}O_{y} near the edge of the superconducting doping regime
X. F. Sun, Kouji Segawa, Yoichi Ando
In-plane transport properties of nonsuperconducting YBa_{2}Cu_{3}O_{y} (y = 6.35) are measured using high-quality untwinned single crystals. We find that both the a- and b-axis res…
Universal critical behavior in single crystals and films of YBaCuO
Hua Xu, Su Li, M. C. Sullivan +4
We have studied the normal-to-superconducting phase transition in optimally-doped YBaCuO in zero external magnetic field using a variety of different samples and t…
Magnetoresistance in Heavily Underdoped YBa_2Cu_3O_{6+x}: Antiferromagnetic Correlations and Normal-State Transport
A. N. Lavrov, Yoichi Ando, Kouji Segawa +1
We report on a contrasting behavior of the in-plane and out-of-plane magnetoresistance (MR) in heavily underdoped antiferromagnetic (AF) YBa_2Cu_3O_{6+x} (x<0.37). The out-of-plane…
Relationship between Fermi-Surface Warping and Out-of-Plane Spin Polarization in Topological Insulators: a View from Spin-Resolved ARPES
M. Nomura, S. Souma, A. Takayama +5
We have performed spin- and angle-resolved photoemission spectroscopy of the topological insulator Pb(Bi,Sb)2Te4 (Pb124) and observed significant out-of-plane spin polarization on…
Doping n-type carriers by La-substitution for Ba in YBa_2Cu_3O_y system
Kouji Segawa, Yoichi Ando
Thus far, there is no cuprate system where both n-type and p-type charge carriers can be doped without changing the crystallographic structure. For studying the electron-hole symme…
Intrinsic Hall response of the CuO2 planes in a chain-plane-composite system of YBa2Cu3Oy
Kouji Segawa, Yoichi Ando
The Hall coefficient is measured in YBaCuO untwinned single crystals for a wide range of doping. We show that the Hall conductivity and the Hall angle of the {\it CuO$_…
Electronic Inhomogeneity and Breakdown of the Universal Thermal Conductivity in Cuprate Superconductors
X. F. Sun, S. Ono, Yasushi Abe +3
We report systematic, high-precision measurements of the low-T (down to 70 mK) thermal conductivity κof YBa_{2}Cu_{3}O_{y}, La_{2-x}Sr_{x}CuO_{4} and Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}.…
Electrodynamics of the Nodal Metal in Weakly Doped High- Cuprates
Y. S. Lee, Kouji Segawa, Z. Q. Li +6
We report on the detailed analysis of the infrared (IR) conductivity of two prototypical high- systems YBaCuO and LaSrCuO throughout t…
Direct Evidence for the Dirac-Cone Topological Surface States in Ternary Chalcogenide TlBiSe2
Takafumi Sato, Kouji Segawa, Hua Guo +4
We have performed high-resolution angle-resolved photoemission spectroscopy on TlBiSe2, which is a member of the ternary chalcogenides theoretically proposed as candidates for a ne…
Spin Polarization of Gapped Dirac Surface States Near the Topological Phase Transition in TlBi(S1-xSex)2
S. Souma, M. Komatsu, M. Nomura +6
We performed systematic spin- and angle-resolved photoemission spectroscopy of TlBi(S1-xSex)2 which undergoes a topological phase transition at x ~ 0.5. In TlBiSe2 (x = 1.0), we re…
Chemical potential jump between hole- and electron-doped sides of ambipolar high-Tc cuprate
M. Ikeda, M. Takizawa, T. Yoshida +3
In order to study an intrinsic chemical potential jump between the hole- and electron-doped high-Tc superconductors, we have performed core-level X-ray photoemission spectroscopy (…
Electrical detection of the spin polarization due to charge flow in the surface state of the topological insulator Bi_1.5 Sb_0.5 Te_1.7 Se_1.3
Yuichiro Ando, Takahiro Hamasaki, Takayuki Kurokawa +7
We detected the spin polarization due to charge flow in the spin non-degenerate surface state of a three dimensional topological insulator by means of an all-electrical method. The…
Quantum Spin Excitations through the metal-to-insulator crossover in
Shiliang Li, Zahra Yamani, Hye Jung Kang +5
We use inelastic neutron scattering to study the temperature dependence of the spin excitations of a detwinned superconducting YBaCuO ( K). In contrast to…
Thermodynamic evidence for nematic superconductivity in CuBiSe
Shingo Yonezawa, Kengo Tajiri, Suguru Nakata +5
Unconventional superconductivity is characterized by the spontaneous symmetry breaking of the macroscopic superconducting wavefunction in addition to the gauge symmetry breaking, s…
Electrochemical synthesis and superconducting phase diagram of Cu_xBi2Se3
M. Kriener, Kouji Segawa, Zhi Ren +4
The superconducting Cu_xBi_2Se_3 is an electron-doped topological insulator and is a prime candidate of the topological superconductor which still awaits discovery. The electrochem…
Unusual nature of fully-gapped superconductivity in In-doped SnTe
Mario Novak, Satoshi Sasaki, Markus Kriener +2
The superconductor Sn_{1-x}In_{x}Te is a doped topological crystalline insulator and has become important as a candidate topological superconductor, but its superconducting phase d…
Manifestation of Topological Protection in Transport Properties of Epitaxial Bi2Se3 Thin Films
A. A. Taskin, Satoshi Sasaki, Kouji Segawa +1
The massless Dirac fermions residing on the surface of three-dimensional topological insulators are protected from backscattering and cannot be localized by disorder, but such prot…
Fermi level tuning and a large activation gap achieved in the topological insulator Bi_{2}Te_{2}Se by Sn doping
Zhi Ren, A. A. Taskin, Satoshi Sasaki +2
We report the effect of Sn doping on the transport properties of the topological insulator Bi_{2}Te_{2}Se studied in a series of Bi_{2-x}Sn_{x}Te_{2}Se crystals with 0 \leq x \leq…
Experimental realization of a topological crystalline insulator in SnTe
Y. Tanaka, Zhi Ren, T. Sato +5
Topological insulators materialize a topological quantum state of matter where unusual gapless metallic state protected by time-reversal symmetry appears at the edge or surface. Th…
Metal-insulator transition and tunable Dirac-cone surface state in the topological insulator TlBi1-xSbxTe2 studied by angle-resolved photoemission
Chi Xuan Trang, Zhiwei Wang, Keiko Yamada +5
We report a systematic angle-resolved photoemission spectroscopy on topological insulator (TI) TlBi1-xSbxTe2 which is bulk insulating at 0.5 < x < 0.9 and undergoes a metal-insulat…
Tunability of the k-space Location of the Dirac Cones in the Topological Crystalline Insulator Pb1-xSnxTe
Y. Tanaka, T. Sato, K. Nakayama +6
We have performed systematic angle-resolved photoemission spectroscopy of the topological crystalline insulator (TCI) Pb1-xSnxTe to elucidate the evolution of its electronic states…
Unveiling quasiparticle dynamics of topological insulators through Bayesian modelling
Satoru Tokuda, Seigo Souma, Kouji Segawa +4
Quasiparticle - a key concept to describe interacting particles - characterizes electron-electron interaction in metals (Fermi liquid) and electron pairing in superconductors. Whil…
Ambipolar transport in bulk crystals of a topological insulator by gating with ionic liquid
Kouji Segawa, Zhi Ren, Satoshi Sasaki +3
We report that the ionic-liquid gating of bulk single crystals of a topological insulator can control the type of the surface carriers and even results in ambipolar transport. This…
Angular-dependent oscillations of the magnetoresistance in Bi_2Se_3 due to the three-dimensional bulk Fermi surface
Kazuma Eto, Zhi Ren, A. A. Taskin +2
We observed pronounced angular-dependent magnetoresistance (MR) oscillations in a high-quality Bi2Se3 single crystal with the carrier density of 5x10^18 cm^-3, which is a topologic…
Mobility of the Doped Holes and the Antiferromagnetic Correlations in Underdoped High-T_c Cuprates
Yoichi Ando, A. N. Lavrov, Seiki Komiya +2
The emergence and the evolution of the metallic charge transport in the La_{2-x}Sr_{x}CuO_{4} system from lightly- to optimally-doped samples (x = 0.01 - 0.17) are studied. We demo…
Carrier concentrations in Bi_{2}Sr_{2-z}La_{z}CuO_{6+δ} single crystals and their relation to Hall coefficient and thermopower
Yoichi Ando, Y. Hanaki, S. Ono +4
We measured the thermopower S and the Hall coefficients R_H of Bi_{2}Sr_{2-z}La_{z}CuO_{6+δ} (BSLCO) single crystals in a wide doping range, in an effort to identify the actual ho…
Doping-dependent charge dynamics in CuxBi2Se3
Luke J. Sandilands, Anjan A. Reijnders, Markus Kriener +4
Superconducting CuxBi2Se3 has attracted significant attention as a candidate topological superconductor. Besides inducing superconductivity, the introduction of Cu atoms to this ma…
The Hall effect in Zn-doped YBa_{2}Cu_{3}O_{7-δ} revisited: Hall angle and the pseudogap
Yasushi Abe, Kouji Segawa, Yoichi Ando
The temperature dependence of the Hall coefficient is measured with a high accuracy in a series of Zn-doped YBCO_{6.78} crystals with the Zn concentration from 0% to 1.3%. We found…
Oscillatory angular dependence of the magnetoresistance in a topological insulator Bi_{1-x}Sb_{x}
A. A. Taskin, Kouji Segawa, Yoichi Ando
The angular-dependent magnetoresistance and the Shubnikov-de Haas oscillations are studied in a topological insulator Bi_{0.91}Sb_{0.09}, where the two-dimensional (2D) surface sta…
Direct Measurement of the Out-of-Plane Spin Texture in the Dirac Cone Surface State of a Topological Insulator
S. Souma, K. Kosaka, T. Sato +6
We have performed spin- and angle-resolved photoemission spectroscopy of Bi2Te3 and present the first direct evidence for the existence of the out-of-plane spin component on the su…