scholarly journals Evidence for a conducting surface ground state in high-quality single crystalline FeSi

2018 ◽  
Vol 115 (34) ◽  
pp. 8558-8562 ◽  
Author(s):  
Yuankan Fang ◽  
Sheng Ran ◽  
Weiwei Xie ◽  
Shen Wang ◽  
Ying Shirley Meng ◽  
...  
Keyword(s):  
Electronic Transport ◽  
Ground State ◽  
Low Temperatures ◽  
Magnetic Order ◽  
Energy Gap ◽  
Charge Carriers ◽  
Conducting Surface ◽  
High Quality ◽  
Metallic Behavior ◽  
Single Crystalline

We report anomalous physical properties of high-quality single-crystalline FeSi over a wide temperature range of 1.8–400 K. The electrical resistivity ρ(T) can be described by activated behavior with an energy gap Δ = 57 meV between 150 and 67 K, below which the estimated energy gap is significantly smaller. The magneto-resistivity and Hall coefficient change sign in the vicinity of 67 K, suggesting a change of dominant charge carriers. At ∼19 K, ρ(T) undergoes a cross-over from semiconducting to metallic behavior which is very robust against external magnetic fields. The low-temperature metallic conductivity depends strongly on the width/thickness of the sample. In addition, no indication of a bulk-phase transition or onset of magnetic order is found down to 2 K from specific heat and magnetic susceptibility measurements. The measurements are consistent with one another and point to complex electronic transport behavior that apparently involves a conducting surface state in FeSi at low temperatures, suggesting the possibility that FeSi is a 3D topological insulator.

Vibronische Kopplung und dynamisch verzerrte Strukturen in Hexahalogenotelluraten(IV): Ergebnisse aus Tieftemperatur-Röntgenbeugungsuntersuchungen (300—160 K) und aus FTIR-spektroskopischen Experimenten (300—5 K) [1] / Vibronic Coupling and Dynamically Distorted Structures in Hexahalogenotellurates(IV): Low Temperatur X-Ray Diffraction (300—160 K) and FTIR-Spectroscopic (300—5 K) Results [1]

1987 ◽  
Vol 42 (10) ◽  
pp. 1273-1281 ◽  
Author(s):  
Walter Abriel ◽  
Ernst-Jürgen Zehnder
Keyword(s):  
Ground State ◽  
Low Temperatures ◽  
Potential Surface ◽  
Energy Gap ◽  
Vibronic Coupling ◽  
High Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Excited State ◽  
Theoretical Considerations

AbstractFrom theoretical considerations a dynamically distorted octahedron as a result of vibronic coupling between the ground state and the first excited state should exist for 14 electron AX6E systems like TeX62- . A high symmetry crystal field yielding at least a center of symmetry for the Te position stabilizes this fluctuating structure, otherwise statical distortion will be observed. From X-ray diffraction experiments on antifluorite type compounds A2TeX6 (A = Rb. Cs: X = Cl, Br) the averaged structure (m3̅m symmetry) of the anions was found even at very low temperatures. The thermal parameters are not significantly different from those of similar SnX62 compounds. Distortions therefore are very small and are evident from FTIR spectroscopic meas­urements only. Here very broad T1u-deformation vibration bands are observed down to tempera­tures <10 K without splitting: Astatically distorted species could not be frozen out. In contrast to XeF6 for TeX62- the energy gap between the threefold, fourfold or sixfold minima of the potential surface (according to the symmetry of one component of the T1u-vibration) is very small and shifted to temperatures lower than reached with the devices used for these experiments.

Ultrathin Single-crystalline MgO (111) Nanosheets

2020 ◽  
Author(s):  
Pengxin Liu ◽  
Paula M. Abdala ◽  
Guillaume Goubert ◽  
Marc Willinger ◽  
Christophe Copéret
Keyword(s):  
Low Temperatures ◽  
Oxygen Vacancies ◽  
High Energy ◽  
Grand Challenge ◽  
High Quality ◽  
Dynamic Vacuum ◽  
Single Crystalline ◽  
Oh Groups ◽  
Single Electrons ◽  
Energy Surfaces

Synthesizing high-quality two-dimensional nanomaterials of non-layered metal oxide is a grand challenge because it requires long range single-crystallinity and clean high-energy surfaces. Here, we report the synthesis of single-crystalline MgO(111) nanosheets via a two-step process involving the formation of ultrathin Mg(OH)<sub>2</sub> nanosheets as precursor and their selective topotactic conversion upon heating under dynamic vacuum. The defect-rich surface displays terminal -OH groups, 3-coordinated O<sup>2-</sup> sites, low-coordinated Mg<sup>2+</sup> sites as well as single electrons trapped at oxygen vacancies, that render MgO nanosheets highly reactive as evidenced by the activation of CO molecules at low temperatures and pressures, with formation of strongly adsorbed red-shifted CO and coupling of CO molecules into C<sub>2</sub> species.

scholarly journals Ultrathin Single-crystalline MgO (111) Nanosheets

2020 ◽  
Author(s):  
Pengxin Liu ◽  
Paula M. Abdala ◽  
Guillaume Goubert ◽  
Marc Willinger ◽  
Christophe Copéret
Keyword(s):  
Low Temperatures ◽  
Oxygen Vacancies ◽  
High Energy ◽  
Grand Challenge ◽  
High Quality ◽  
Dynamic Vacuum ◽  
Single Crystalline ◽  
Oh Groups ◽  
Single Electrons ◽  
Energy Surfaces

Synthesizing high-quality two-dimensional nanomaterials of non-layered metal oxide is a grand challenge because it requires long range single-crystallinity and clean high-energy surfaces. Here, we report the synthesis of single-crystalline MgO(111) nanosheets via a two-step process involving the formation of ultrathin Mg(OH)<sub>2</sub> nanosheets as precursor and their selective topotactic conversion upon heating under dynamic vacuum. The defect-rich surface displays terminal -OH groups, 3-coordinated O<sup>2-</sup> sites, low-coordinated Mg<sup>2+</sup> sites as well as single electrons trapped at oxygen vacancies, that render MgO nanosheets highly reactive as evidenced by the activation of CO molecules at low temperatures and pressures, with formation of strongly adsorbed red-shifted CO and coupling of CO molecules into C<sub>2</sub> species.

Structural properties, magnetic order and electronic transport in single crystalline UPt2Si2

2010 ◽  
Vol 322 (17) ◽  
pp. 2447-2453 ◽  
Author(s):  
M. Bleckmann ◽  
A. Otop ◽  
S. Süllow ◽  
R. Feyerherm ◽  
J. Klenke ◽  
...  
Keyword(s):  
Structural Properties ◽  
Electronic Transport ◽  
Magnetic Order ◽  
Single Crystalline

scholarly journals Gapless quantum spin liquid in a honeycomb Γ magnet

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Qiang Luo ◽  
Jize Zhao ◽  
Hae-Young Kee ◽  
Xiaoqun Wang
Keyword(s):  
Ground State ◽  
Magnetic Order ◽  
Energy Gap ◽  
Entanglement Entropy ◽  
Quantum Spin ◽  
Spin Liquid ◽  
Spin Liquids ◽  
Complete Understanding ◽  
Quantum Spin Liquids ◽  
Quantum Spin Liquid

AbstractA family of spin–orbit coupled honeycomb Mott insulators offers a playground to search for quantum spin liquids (QSLs) via bond-dependent interactions. In candidate materials, a symmetric off-diagonal Γ term, close cousin of Kitaev interaction, has emerged as another source of frustration that is essential for complete understanding of these systems. However, the ground state of honeycomb Γ model remains elusive, with a suggested zigzag magnetic order. Here we attempt to resolve the puzzle by perturbing the Γ region with a staggered Heisenberg interaction which favours the zigzag ordering. Despite such favour, we find a wide disordered region inclusive of the Γ limit in the phase diagram. Further, this phase exhibits a vanishing energy gap, a collapse of excitation spectrum, and a logarithmic entanglement entropy scaling on long cylinders, indicating a gapless QSL. Other quantities such as plaquette-plaquette correlation are also discussed.

Zur Berechnung der chemischen Verschiebung unter besonderer Berücksichtigung des paramagnetischen Terms / Attempts to the Calculation of the Chemical Shift with Especial Consideration of the Paramagnetic Term

1977 ◽  
Vol 32 (12) ◽  
pp. 1541-1543
Author(s):  
H. Sterk ◽  
J. J. Suschnigg
Keyword(s):  
Chemical Shift ◽  
Excited States ◽  
Ground State ◽  
Energy Gap

Abstract Attempts to the Calculation of the Chemical Shift with Especial Consideration of the Paramagnetic Term The calculation of the paramagnetic term according to the Pople formalism of the chemical shift is expanded. The hitherto constant value of the energy gap between the ground state and the excited states is replaced by the value of the lowest lying excitation. This leads to a remarkably better differentiation of the paramagnetic terms of different compounds. The influence is shown on ethane, ethene and ethine.

scholarly journals Intrinsic Electronic Transport Properties of High-Quality Monolayer and Bilayer MoS2

Nano Letters ◽  
2013 ◽  
Vol 13 (9) ◽  
pp. 4212-4216 ◽  
Author(s):  
Britton W. H. Baugher ◽  
Hugh O. H. Churchill ◽  
Yafang Yang ◽  
Pablo Jarillo-Herrero
Keyword(s):  
Transport Properties ◽  
Electronic Transport ◽  
High Quality ◽  
Electronic Transport Properties

Magnetic Quantum Oscillations from Surface States of Bi Nanowires

2011 ◽  
Vol 1350 ◽  
Author(s):  
L. A. Konopko ◽  
T. E. Huber ◽  
A. A. Nikolaeva
Keyword(s):  
Single Crystal ◽  
Low Temperatures ◽  
Surface States ◽  
Charge Carriers ◽  
Quantum Oscillations ◽  
Wide Range ◽  
Spin Orbit Interactions ◽  
Conducting Tube ◽  
Magnetic Quantum Oscillations ◽  
Strong Spin

ABSTRACTIn this work, we report the results of studies of the transverse magnetoresistance (MR) of single-crystal Bi nanowires with diameter d<80 nm. The single-crystal nanowire samples were prepared by the Taylor-Ulitovsky technique. Due to the semimetal-to-semiconductor transformation and high density of surface states with strong spin-orbit interactions, the charge carriers are confined to the conducting tube made of surface states. The non monotonic changes of transverse MR that are equidistant in a direct magnetic field were observed at low temperatures in a wide range of magnetic fields up to 14 T. The period of oscillations depends on the wire diameter d as for the case of longitudinal MR. An interpretation of transverse MR oscillations is presented.

LOW-TEMPERATURE NORMAL-STATE HALL EFFECT IN HIGH-TcBi2Sr2-xLaxCuO6+δ REVEALED BY 60 T MAGNETIC FIELDS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3171-3174
Author(s):  
F. F. BALAKIREV ◽  
J. B. BETTS ◽  
G. S. BOEBINGER ◽  
S. ONO ◽  
Y. ANDO ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Carrier Concentration ◽  
Hall Coefficient ◽  
Normal State ◽  
Ground State ◽  
Low Temperatures ◽  
Optimal Doping ◽  
Underdoped Sample ◽  
Additional Support

We report low-temperature Hall coefficient in the normal state of the high-Tc superconductor Bi 2 Sr 2-x La x CuO 6+δ. The Hall coefficient was measured down to 0.5 K by suppressing superconductivity with a 60 T pulsed magnetic field. The carrier concentration was varied from overdoped to underdoped regimes by partially substituting Sr with La in a set of five samples. The observed saturation of the Hall coefficient at low temperatures suggests the ability to extract the carrier concentration of each sample. The most underdoped sample exhibits a diverging Hall coefficient at low temperatures, consistent with a depletion of carriers in the insulating ground state. The Hall number exhibits a sharp peak providing additional support for the existence of a phase boundary at the optimal doping.

scholarly journals Anomalous and anisotropic nonlinear susceptibility in the proximate Kitaev magnet α-RuCl3

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Ludwig Holleis ◽  
Joseph C. Prestigiacomo ◽  
Zhijie Fan ◽  
Satoshi Nishimoto ◽  
Michael Osofsky ◽  
...  
Keyword(s):  
Low Temperatures ◽  
High Field ◽  
Magnetic Order ◽  
Exact Diagonalization ◽  
Nonlinear Susceptibility ◽  
Magnetic Response ◽  
Leading Order ◽  
Rapid Rise ◽  
Quadratic Response ◽  
Antiferromagnetic Behavior

AbstractThe leading order nonlinear (NL) susceptibility, χ3, in a paramagnet is negative and diverges as T → 0. This divergence is destroyed when spins correlate and the NL response provides unique insights into magnetic order. Dimensionality, exchange interaction, and preponderance of quantum effects all imprint their signatures in the NL magnetic response. Here, we study the NL susceptibilities in the proximate Kitaev magnet α-RuCl3, which differs from the expected antiferromagnetic behavior. For T < Tc = 7.5 K and field B in the ab-plane, we obtain contrasting NL responses in low (<2 T) and high field regions. For low fields, the NL behavior is dominated by a quadratic response (positive χ2), which shows a rapid rise below Tc. This large χ2 > 0 implies a broken sublattice symmetry of magnetic order at low temperatures. Classical Monte Carlo (CMC) simulations in the standard K − H − Γ model secure such a quadratic B dependence of M, only for T ≈ Tc with χ2 being zero as T → 0. It is also zero for all temperatures in exact diagonalization calculations. On the other hand, we find an exclusive cubic term (χ3) that describes the high field NL behavior well. χ3 is large and positive both below and above Tc crossing zero only for T > 50 K. In contrast, for B ∥ c-axis, no separate low/high field behaviors are measured and only a much smaller χ3 is apparent.

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