Excitonic and Nematic Instabilities on the Surface of Topological Kondo Insulators

Abstract

We study the effects of strong electron-electron interactions on the surface of cubic topological Kondo insulators (such as samarium hexaboride, SmB${}_6$). Cubic topological Kondo insulators generally support three copies of massless Dirac nodes on the surface, but only two of them are energetically degenerate and exhibit an energy offset relative to the third one. With a tunable chemical potential, when the surface states host electron and hole pockets of comparable size, strong interactions may drive this system into rotational symmetry breaking nematic and translational symmetric breaking excitonic spin- or charge-density-wave phases, depending on the relative chirality of the Dirac cones. Taking a realistic surface band structure into account we analyze the associated Ginzburg-Landau theory and compute the mean field phase diagram for interacting surface states. Beyond mean field theory, this system can be described by a two-component isotropic Ashkin-Teller model at finite temperature, and we outline the phase diagram of this model. Our theory provides a possible explanation of recent measurements which detect a two-fold symmetric magnetoresistance and an upturn in surface resistivity with tunable gate voltage in SmB${}_6$. Our discussion can also be germane to other cubic topological insulators, such as ytterbium hexaboride (YbB${}_6$), plutonium hexaboride (PuB${}_6$).

9+epsilon pages, 3 figures: Published version, added discussion and new references

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Cited by in corpus (17)

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• Emergence of supersymmetric quantum electrodynamics
• Quantum Multicriticality near the Dirac-Semimetal to Band-Insulator Critical Point in Two Dimensions: A Controlled Ascent from One Dimension
• Double stage nematic bond-ordering above double stripe magnetism: application to BaTi${}_2$Sb${}_2$O
• Spin textures on general surfaces of the correlated topological insulator SmB6
• Cascade of vestigial orders in two-component superconductors: nematic, ferromagnetic, s-wave charge-4e, and d-wave charge-4e states
• Scanning tunneling spectroscopy as a probe of multi-Q magnetic states of itinerant magnets
• Ferromagnetism and glassiness on the surface of topological insulators
• Topology and Magnetism in the Kondo Insulator Phase Diagram
• Interacting topological phases in thin films of topological mirror Kondo insulators
• Spontaneous symmetry breaking and quantum Hall valley ordering on the surface of topological hexaborides
• Nematic order on the surface of a three-dimensional topological insulator
• Prediction of at topological $p+ip$ excitonic insulator with parity anomaly
• Half vortex and fractional electrical charge in two dimensions
• Fermi surface instabilities of symmetry-breaking and topological types on the surface of a three-dimensional topological insulator
• Superconductivity in three-dimensional interacting doped topological insulators
• Emergent Ising degrees of freedom above double-stripe magnetism