The energy gap of intermediate-valent SmB6 studied by point-contact spectroscopy

Abstract

We have investigated the intermediate valence narrow-gap semiconductor SmB6 at low temperatures using both conventional spear-anvil type point contacts as well as mechanically controllable break junctions. The zero-bias conductance varied between less than 0.01 mikrosiemens and up to 1 mS. The position of the spectral anomalies, which are related to the different activation energies and band gaps of SmB6, did not depend on the the contact size. Two different regimes of charge transport could be distinguished: Contacts with large zero - bias conductance are in the diffusive Maxwell regime. They had spectra with only small non-linearities. Contacts with small zero - bias conductance are in the tunnelling regime. They had larger anomalies, but still indicating a finite 45 % residual quasiparticle density of states at the Fermi level at low temperatures of T = 0.1 K. The density of states derived from the tunelling spectra can be decomposed into two energy-dependent parts with Eg = 21 meV and Ed = 4.5 meV wide gaps, respectively.

9 pages incl. 13 figures

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• Momentum-Dependent Hybridization Gap and dispersive in-gap state of The Kondo Semiconductor SmB6
• Additional energy scale in SmB${}_6$ at low temperature
• Large, high quality single-crystals of the new Topological Kondo Insulator, SmB6
• SmB6 Photoemission: Past and Present
• Magnetic and defect probes of the SmB${}_6$ surface state
• Breakdown of the Kondo insulating state in SmB6 by introducing Sm vacancies
• Bulk and surface electronic properties of SmB6: a hard x-ray photoelectron spectroscopy study
• Temperature Dependence of Linked Gap and Surface State Evolution in the Mixed Valent Topological Insulator SmB6
• Non-trivial surface states of samarium hexaboride at the (111) surface
• Two-dimensional heavy fermions on the strongly correlated boundaries of Kondo topological insulators
• A highly asymmetric nodal semimetal in bulk SmB6
• The Effects of Spin-Excitons on the Surface States of SmB6: A Photoemission Study
• Planar tunneling spectroscopy of the topological Kondo insulator SmB${}_6$
• Reduction of the low-temperature bulk gap in samarium hexaboride under high magnetic fields
• Understanding low-temperature bulk transport in samarium hexaboride without relying on in-gap bulk states
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• Universal properties of the near-gap spectra of SmB6: dynamical mean-field calculations and photoemission experiments
• Probing the interplay between surface and bulk states in the topological Kondo insulator SmB${}_6$ through conductance fluctuation spectroscopy
• Systematic electrochemical etching of various metal tips for tunneling spectroscopy and scanning probe microscopy
• An STM perspective on hexaborides: Surface states of the Kondo insulator SmB${}_6$
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• Hall coefficient diagnostics of surface state in pressurized SmB6
• Spatial interferences in the electron transport of heavy fermion materials
• An experimental algorithm for identifying the topological nature of Kondo and mixed valence insulators