Critical examination of quantum oscillations in 
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Riseborough, Peter S.; Fisk, Z.

doi:10.1103/physrevb.96.195122

Cited by 15 publications

(12 citation statements)

References 42 publications

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“…Broad classes of models that have been proposed to explain bulk quantum oscillations in unconventional insulators include categories of gapped models, and models characterised by in-gap low energy excitations [12][13][14][15][16][17][18][19][20][21][22][23]. An analysis of the temperature-dependence of the quantum oscillation amplitude provides us with vital information to distinguish between classes of gapped and gapless models to describe quantum oscillations in the unconventional insulating phase.…”

Section: Field-induced Metallic Regimesmentioning

confidence: 99%

“…At the simplest level of weakly interacting gapped systems, the system is characterised by a single particle gap. Models in this category have for example been proposed for BCS superconductors [12] and for weakly interacting insulators [13,14]. Examples of such behaviour are experimentally observed in unconventional superconductors [24][25][26][27].…”

Section: Field-induced Metallic Regimesmentioning

confidence: 99%

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$f$-electron hybridised metallic Fermi surface in magnetic field-induced metallic YbB$_{12}$

Liu,

Hickey,

Hartstein

et al. 2021

Preprint

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The nature of the Fermi surface observed in the recently discovered family of unconventional insulators starting with SmB 6 and subsequently YbB 12 is a subject of intense inquiry. Here we shed light on this question by comparing quantum oscillations between the high magnetic field-induced metallic regime in YbB 12 and the unconventional insulating regime. In the field-induced metallic regime beyond 47 T, we find prominent quantum oscillations in the contactless resistivity characterised by multiple frequencies up to at least 3000 T and heavy effective masses up to at least 17 𝑚 e , characteristic of an 𝑓 -electron hybridised metallic Fermi surface. The growth of quantum oscillation amplitude at low temperatures in electrical transport and magnetic torque in insulating YbB 12 is closely similar to the Lifshitz-Kosevich low temperature growth of quantum oscillation amplitude in field-induced metallic YbB 12 , pointing to an origin of quantum oscillations in insulating YbB 12 from in-gap neutral low energy excitations. The field-induced metallic regime of YbB 12 is characterised by more Fermi surface sheets of heavy quasiparticle effective mass that emerge in addition to the heavy Fermi surface sheets yielding multiple quantum oscillation frequencies below 1000 T observed in both insulating and metallic regimes. We thus observe a heavy multi-component Fermi surface in which 𝑓electron hybridisation persists from the unconventional insulating to the fieldinduced metallic regime of YbB 12 , which is in distinct contrast to the unhybridised conduction electron Fermi surface observed in the case of the unconventional insulator SmB 6 . Our findings require a different theoretical model of neutral in-gap low energy excitations in which the 𝑓 -electron hybridisation is retained in the case of the unconventional insulator YbB 12 .

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Section: Field-induced Metallic Regimesmentioning

confidence: 99%

Section: Field-induced Metallic Regimesmentioning

confidence: 99%

$f$-electron hybridised metallic Fermi surface in magnetic field-induced metallic YbB$_{12}$

Liu,

Hickey,

Hartstein

et al. 2021

Preprint

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“…Some of these scenarios have included oscillations by excitonic states [35,36] or a Majorana fermion band that breaks gauge symmetry [37,38]. Others have proposed a breakdown of the gap under magnetic field [39,40] or ways for oscillations to occur in gapped systems based on the unhybridized band structure or as an effect of the band edges [41,42].…”

Section: Introductionmentioning

confidence: 99%

Bulk transport paths through defects in floating zone and Al flux grown SmB6

Rakoski

Sinha

et al. 2021

Phys. Rev. Materials

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We investigate the roles of disorder on low-temperature transport in SmB 6 crystals grown by both the Al flux and floating zone methods. We used the inverted resistance method with Corbino geometry to investigate whether low-temperature variations in the standard resistance plateau arise from a surface or a bulk channel in floating zone samples. The results show significant sample-dependent residual bulk conduction, in contrast to smaller amounts of residual bulk conduction previously observed in Al flux grown samples with Sm vacancies. We consider hopping in an activated impurity band as a possible source for the observed bulk conduction, but it is unlikely that the large residual bulk conduction seen in floating zone samples is solely due to Sm vacancies. We therefore propose that one-dimensional defects, or dislocations, contribute as well. Using chemical etching, we find evidence for dislocations in both flux and floating zone samples, with higher dislocation density in floating zone samples than in Al flux grown samples. In addition to the possibility of transport through one-dimensional dislocations, we also discuss our results in the context of recent theoretical models of SmB 6 .

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“…Our surprising finding of quantum oscillations in the magnetic torque of floating zone-grown single crystals of SmB 6 ( Tan et al., 2015 ), despite the bulk insulating gap, has given rise to multiple proposals for their potential origin. Physical mechanisms proposed as potential explanations for the observed quantum oscillations include bulk in-gap low energy excitations ( Tan et al., 2015 ; Hartstein et al., 2018 ), two-dimensional surface conduction states ( Li et al., 2014 ), tunneling across the bulk insulating gap ( Knolle and Cooper, 2015 , 2017 ), and impurity inclusions ( Thomas et al., 2019 ; Fuhrman et al., 2018 ; Fuhrman and Nikolić, 2020 ), among others ( Baskaran, 2015 ; Knolle and Cooper, 2015 , 2017 ; Erten et al., 2016 , 2017 ; Chowdhury et al., 2018 ; Sodemann et al., 2018 ; Thomson and Sachdev, 2016 ; Skinner, 2019 ; Peters et al., 2019 ; Liu and Balents, 2017 ; Shen and Fu, 2018 ; Valentine et al., 2016 ; Harrison, 2018 ; Zhang et al., 2016 ; Pal, 2017 ; Riseborough and Fisk, 2017 ; Grubinskas and Fritz, 2018 ; Sakhya and Maiti, 2020 ; Pixley et al., 2018 ; Ram and Kumar, 2017 ; Anderson, 1992 ; Coleman et al., 1993 ; Motrunich, 2006 ; Grover et al., 2010 ; Paul et al., 2007 ; Kishigi and Hasegawa, 2014 ).…”

Section: Introductionmentioning

confidence: 99%

Intrinsic Bulk Quantum Oscillations in a Bulk Unconventional Insulator SmB6

et al. 2020

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Summary The finding of bulk quantum oscillations in the Kondo insulator SmB 6 proved a considerable surprise. Subsequent measurements of bulk quantum oscillations in other correlated insulators including YbB 12 lent support to our discovery of a class of bulk unconventional insulators that host bulk quantum oscillations. Here we perform a series of experiments to examine evidence for the intrinsic character of bulk quantum oscillations in floating zone-grown single crystals of SmB 6 that have been the subject of our quantum oscillation studies. We present results of thermodynamic, transport, and composition analysis experiments on pristine floating zone-grown single crystals of SmB 6 and compare quantum oscillations with metallic LaB 6 and elemental aluminum. These results establish the intrinsic origin of quantum oscillations from the insulating bulk of floating zone-grown SmB 6 . The similarity of the Fermi surface in insulating SmB 6 with the conduction-electron Fermi surface in metallic hexaborides is at the heart of a theoretical mystery.

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Critical examination of quantum oscillations in SmB6

Cited by 15 publications

References 42 publications

$f$-electron hybridised metallic Fermi surface in magnetic field-induced metallic YbB$_{12}$

$f$-electron hybridised metallic Fermi surface in magnetic field-induced metallic YbB$_{12}$

Bulk transport paths through defects in floating zone and Al flux grown SmB6

Intrinsic Bulk Quantum Oscillations in a Bulk Unconventional Insulator SmB6

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