Conductance Quantization at Zero Magnetic Field in InSb Nanowires

AbstractDetecting conductance quantization in graphene nanostructures turned out more challenging than expected. The observation of well-defined conductance plateaus through graphene nanoconstrictions so far has only been accessible in the highest quality suspended or h-BN encapsulated devices. However, reaching low conductance quanta in zero magnetic field, is a delicate task even with such ultra-high mobility devices. Here, we demonstrate a simple AFM-based nanopatterning technique for defining graphene constrictions with high precision (down to 10 nm width) and reduced edge-roughness (+/−1 nm). The patterning process is based on the in-plane mechanical cleavage of graphene by the AFM tip, along its high symmetry crystallographic directions. As-defined, narrow graphene constrictions with improved edge quality enable an unprecedentedly robust QPC operation, allowing the observation of conductance quantization even on standard SiO2/Si substrates, down to low conductance quanta. Conductance plateaus, were observed at n × e2/h, evenly spaced by 2 × e2/h (corresponding to n = 3, 5, 7, 9, 11) in the absence of an external magnetic field, while spaced by e2/h (n = 1, 2, 3, 4, 5, 6) in 8 T magnetic field.

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Experimental signatures of nodeless multiband superconductivity in a $$\hbox {2H-Pd}_{0.08} \hbox {TaSe}_2$$ single crystal

Scientific Reports ◽

10.1038/s41598-021-92709-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Chanhee Kim ◽

Dilip Bhoi ◽

Yeahan Sur ◽

Byung-Gu Jeon ◽

Dirk Wulferding ◽

...

Keyword(s):

Magnetic Field ◽

Single Crystal ◽

Zero Magnetic Field ◽

Anisotropy Ratio ◽

Strong Temperature Dependence ◽

Critical Fields ◽

Band Theory ◽

Plane Field ◽

Low Field ◽

Out Of Plane

AbstractIn order to understand the superconducting gap nature of a $$\hbox {2H-Pd}_{0.08} \hbox {TaSe}_2$$ 2H-Pd 0.08 TaSe 2 single crystal with $$T_{c} = 3.13 \text { K}$$ T c = 3.13 K , in-plane thermal conductivity $$\kappa $$ κ , in-plane London penetration depth $$\lambda _{\text {L}}$$ λ L , and the upper critical fields $$H_{c2}$$ H c 2 have been investigated. At zero magnetic field, it is found that no residual linear term $$\kappa _{0}/T$$ κ 0 / T exists and $$\lambda _{\text {L}}$$ λ L follows a power-law $$T^n$$ T n (T: temperature) with n = 2.66 at $$T \le \frac{1}{3}T_c$$ T ≤ 1 3 T c , supporting nodeless superconductivity. Moreover, the magnetic-field dependence of $$\kappa _{0}$$ κ 0 /T clearly shows a shoulder-like feature at a low field region. The temperature dependent $$H_{c2}$$ H c 2 curves for both in-plane and out-of-plane field directions exhibit clear upward curvatures near $$T_c$$ T c , consistent with the shape predicted by the two-band theory and the anisotropy ratio between the $$H_{c2}$$ H c 2 (T) curves exhibits strong temperature-dependence. All these results coherently suggest that $$\hbox {2H-Pd}_{0.08} \hbox {TaSe}_2$$ 2H-Pd 0.08 TaSe 2 is a nodeless, multiband superconductor.

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Imaging the formation and surface phase separation of the CE phase

npj Quantum Materials ◽

10.1038/s41535-021-00353-2 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Haibiao Zhou ◽

Qiyuan Feng ◽

Yubin Hou ◽

Masao Nakamura ◽

Yoshinori Tokura ◽

...

Keyword(s):

Magnetic Field ◽

Phase Transitions ◽

Charge Ordering ◽

Zero Magnetic Field ◽

Ferromagnetic Phase ◽

Emergent Properties ◽

Orbital Ordering ◽

Strong Electron ◽

Antiferromagnetic Correlation ◽

Ordering Transitions

AbstractThe CE phase is an extraordinary phase exhibiting the simultaneous spin, charge, and orbital ordering due to strong electron correlation. It is an ideal platform to investigate the role of the multiple orderings in the phase transitions and discover emergent properties. Here, we use a cryogenic high-field magnetic force microscope to image the phase transitions and properties of the CE phase in a Pr0.5Ca0.5MnO3 thin film. In a high magnetic field, we observed a clear suppression of magnetic susceptibility at the charge-ordering insulator transition temperature (TCOI), whereas, at the Néel temperature (TN), no significant change is observed. This observation favors the scenario of strong antiferromagnetic correlation developed below TCOI but raises questions about the Zener polaron paramagnetic phase picture. Besides, we discoverd a phase-separated surface state in the CE phase regime. Ferromagnetic phase domains residing at the surface already exist in zero magnetic field and show ultra-high magnetic anisotropy. Our results provide microscopic insights into the unconventional spin- and charge-ordering transitions and revealed essential attributes of the CE phase, highlighting unusual behaviors when multiple electronic orderings are involved.

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Lower bounds for the first eigenvalue of the Laplacian with zero magnetic field in planar domains

Journal of Functional Analysis ◽

10.1016/j.jfa.2021.108999 ◽

2021 ◽

pp. 108999

Author(s):

Bruno Colbois ◽

Alessandro Savo

Keyword(s):

Magnetic Field ◽

Lower Bounds ◽

Zero Magnetic Field ◽

First Eigenvalue ◽

The First Eigenvalue ◽

Planar Domains

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Colossal anomalous Nernst effect in a correlated noncentrosymmetric kagome ferromagnet

Science Advances ◽

10.1126/sciadv.abf1467 ◽

2021 ◽

Vol 7 (13) ◽

pp. eabf1467

Author(s):

T. Asaba ◽

V. Ivanov ◽

S. M. Thomas ◽

S. Y. Savrasov ◽

J. D. Thompson ◽

...

Keyword(s):

Magnetic Field ◽

Electronic Structure ◽

Theoretical Calculations ◽

Zero Magnetic Field ◽

Nernst Effect ◽

Nodal Lines ◽

Transverse Response ◽

Narrow Bands ◽

Strong Spin ◽

Anomalous Nernst Effect

The transverse voltage generated by a temperature gradient in a perpendicularly applied magnetic field, termed the Nernst effect, has promise for thermoelectric applications and for probing electronic structure. In magnetic materials, an anomalous Nernst effect (ANE) is possible in a zero magnetic field. We report a colossal ANE in the ferromagnetic metal UCo0.8Ru0.2Al, reaching 23 microvolts per kelvin. Uranium’s 5f electrons provide strong electronic correlations that lead to narrow bands, a known route to producing a large thermoelectric response. In addition, uranium’s strong spin-orbit coupling produces an intrinsic transverse response in this material due to the Berry curvature associated with the relativistic electronic structure. Theoretical calculations show that in UCo0.8Ru0.2Al at least 148 Weyl nodes, and two nodal lines, exist within 60 millielectron volt of the Fermi level. This work demonstrates that magnetic actinide materials can host strong Nernst and Hall responses due to their combined correlated and topological nature.

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TRANSPORT PROPERTIES OF 2D ELECTRON GAS IN AN n-InGaAs/GaAs DQW IN A VICINITY OF LOW MAGNETIC-FIELD-INDUCED HALL INSULATOR–QUANTUM HALL LIQUID TRANSITION

International Journal of Nanoscience ◽

10.1142/s0219581x07004523 ◽

2007 ◽

Vol 06 (03n04) ◽

pp. 173-177

Author(s):

YU. G. ARAPOV ◽

S. V. GUDINA ◽

G. I. HARUS ◽

V. N. NEVEROV ◽

N. G. SHELUSHININA ◽

...

Keyword(s):

Magnetic Field ◽

Electron Gas ◽

Quantum Hall ◽

Zero Magnetic Field ◽

Double Quantum ◽

Ballistic Regime ◽

2D Electron Gas ◽

Double Quantum Well ◽

Liquid Transition ◽

Low Magnetic Field

The resistivity (ρ) of low mobility dilute 2D electron gas in an n- InGaAs / GaAs double quantum well (DQW) exhibits the monotonic "insulating-like" temperature dependence (dρ/dT < 0) at T = 1.8–70 K in zero magnetic field. This temperature interval corresponds to a ballistic regime (kBTτ/ħ > 0.1–3.5) for our samples, and the electron density is on an "insulating" side of the so-called B = 0 2D metal–insulator transition. We show that the observed features of localization and Landau quantization in a vicinity of the low magnetic-field-induced insulator–quantum Hall liquid transition is due to the σxy(T) anomalous T-dependence.

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