Inducing magnetism onto the surface of a topological crystalline insulator

Assaf, Badih A.; Katmis, Ferhat; Peng, Wei; Chang, Cui Zu; Satpati, Biswarup; Moodera, Jagadeesh S.; Heiman, D.

doi:10.1103/physrevb.91.195310

Cited by 35 publications

(31 citation statements)

References 55 publications

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“…22 It is also possible that lattice mismatch may slightly change the out-of-plane bond length and affect the interfacial polarity, leading to the observed change in nonlinear susceptibility.…”

Section: Resultsmentioning

confidence: 99%

“…11,12,16,17 The SCR is formed by accumulation of Se vacancies upon exposed to air. 12,[15][16][17] Because the interface between Bi 2 Se 3 and BaF 2 has only little amount of vacancies or defects, 22 we neglect the SCR effect near that interface. If !…”

Section: For Transmitted Sh Beam (2 ) Generated By a Polarization Shementioning

confidence: 99%

“…We were also able to obtain the value of the bulk third-order nonlinear susceptibility for the dc-field-induced second-order nonlinearity that can be used to monitor the surface field in the SCR. Moreover, we extracted contribution from the buried Bi 2 Se 3 /BaF 2 interface that is usually difficult to access, 21,22 and found it to have a much stronger out-of-plane polar ordering compared to the air/Bi 2 Se 3 interface.…”

Section: Introductionmentioning

confidence: 99%

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Surface and bulk contributions to the second-harmonic generation in Bi2Se3

Shi

Yao

et al. 2016

Phys. Rev. B

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Second harmonic generation (SHG) from three-dimensional topological insulators originates from both surface and bulk, which does not allow probing of surface states unless the measurement can separate the two contributions. In this study, we used combined measurements of transmitted and reflected SHG from epitaxially grown Bi 2 Se 3 thin films of different thickness on BaF 2 , and a bulk Bi 2 Se 3 crystal, to deduce surface and bulk nonlinear susceptibilities of Bi 2 Se 3 separately. We found that the surface * E-mail: yrshen@berkeley.edu, wtliu@fudan.edu.cn 2 contribution to SHG was comparable to that from the bulk of the crystal, but becomes dominant in ultrathin films. In the latter case, contributions from both air/Bi 2 Se 3 and Bi 2 Se 3 /BaF 2 interfaces were significant, and exhibited a strong out-of-plane polar ordering. The bulk contribution came mainly from the space charge region (SCR), which was formed by Se vacancies aggregated at the air/Bi 2 Se 3 interface; its magnitude can provide an estimate on the field strength in the SCR. Clarification of surface and bulk contributions to SHG can help nonlinear optical techniques be used as a versatile in situ probe for topological insulators.3

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Section: Resultsmentioning

confidence: 99%

Section: For Transmitted Sh Beam (2 ) Generated By a Polarization Shementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surface and bulk contributions to the second-harmonic generation in Bi2Se3

Shi

Yao

et al. 2016

Phys. Rev. B

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“…The valley degeneracy and anisotropy of IV-VI materials also need to be accounted for. When B|| [1][2][3][4][5][6][7][8][9][10], the Fermi surface consists of two ellipsoidal valleys having their major axis tilted by θ=90⁰, and two others tilted by θ=35⁰ with respect to B (Fig. S2) Table I.…”

Section: Fig 2 (Color Online) (A)mentioning

confidence: 99%

“…We correlate the appearance of the NLMR to the crossing of the N=1 LL with the Fermi energy (Ef), by looking at 3D Shubnikov-de-Haas (SdH) oscillations measured in the same geometry as the MR (I // B // [1][2][3][4][5][6][7][8][9][10]). Fig.2(b) shows SdH oscillations in the second derivative of the resistance for x=0.14 and x=0.19 at 10K.…”

Section: Fig 2 (Color Online) (A)mentioning

confidence: 99%

Negative Longitudinal Magnetoresistance from the Anomalous N=0 Landau Level in Topological Materials

et al. 2017

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Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and DC field measurements on Pb1-xSnxSe epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest N=0 conduction Landau level disperses down in energy as a function of increasing magnetic field, while the N=0 valence Landau level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter. [13]. This stems from the helical Dirac nature of surface-states in 3D TIs or, that of edge-states in 2D TIs. In fact, a huge amount of literature (for reviews [14] [15] [16] [17]) took interest in this question and investigated electronic transport of 2D Dirac electrons in 3D-TIs. The majority of these studies were, however, impeded by the significant and dominant bulk transport that occurs in TIs. On the other hand, little attention has been given to signatures of non-trivial band topology in 3D electron transport in a TI.Naively speaking, one can think of the bulk energy bands of a TI as being identical to those of conventional semiconductors and, thus, unlikely to generate non-conventional physical phenomena. However, one should not forget that the basis of a topological insulator lies in the inverted orbital character of these bulk energy bands. [23] shown, that the energy of the lowest (N=0) conduction (valence) Landau level in topological insulators decreases (increases) as a function of increasing magnetic field, opposite to what usually happens in a topologically trivial system ( Fig.1(a,b)). This behavior is anomalous and leads to a field-induced closure of the energy gap in a TI [21] (Fig.1(b)), whereas in a trivial material, the energy gap usually opens with increasing magnetic field ( Fig.1(a)). This anomaly is a hallmark of the inverted band structure of topological materials. Its implications on magnetotransport have not yet been considered. In the present work, we study the MR in topological insulators in the extreme quantum limit -the regime where only the lowest Landau level (LL) is occupied. We measure magnetotransport in pulsed magnetic field up to 61T in high mobility Pb1-xSnxSe epitaxial layers. We show that, when all Lorentz components contributing to the MR are suppressed by applying the magnetic field in-plane and parallel to the excitation current, a negative longitudinal MR (NLMR) emerges near the onset of the quantum limit. This NLMR is only observed in the topological regime of Pb1-xSnxSe (x>0.16) and is absent in trivial samples (x<0.16). We theoretically argue that this NLMR is a result of the anomalous beh...

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Giant Rashba Splitting in Pb_1–_xSn_xTe (111) Topological Crystalline Insulator Films Controlled by Bi Doping in the Bulk

et al. 2016

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to external perturbations. [10,15,16] Therefore, the trivial to nontrivial topological phase transition can be controlled by many different means, such as by varying temperature, [1,6] pressure, [2] hybridization in ultrathin film geometries, [17][18][19] magnetic interactions, [20] or by breaking of mirror symmetries by strain, [16,[21][22][23] electrostatic fields, [18] or ferroelectric (FE) lattice distortions. [24,25] This provides ample degrees of freedom for topology control not available in conventional Z 2 TIs. For this reason, TCIs offer an ideal template for observation of exotic phenomena such as partially flat band helical snake states and interfacial superconductivity, [16] large-Chern-number quantum anomalous Hall effect, [26] as well as for realization of novel topology-based devices such as topological photodetectors, [23] spin transistors, [18] and spin torque devices. [27] For most of such applications, thin film structures with precisely controlled composition and Fermi level are required. Up to now, most work has been performed on highly p-type bulk crystals exploiting the natural (001) cleavage plane of the IV-VI compounds, [3,4,6] whereas for other surface orientations and practical devices epitaxial TCI film structures are required. [18,[28][29][30][31][32] The (111) orientation is particularly interesting due to the polar nature of its surface [12] as well as the ease of lifting the fourfold valley degeneracy at the L-points of the Brillouin zone (BZ) [33] by opening a gap at particular Dirac points by strain [16] and quantum confinement [17][18][19] to induce a transition from a TCI to a normal Z 2 -TI material. [25]

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Inducing magnetism onto the surface of a topological crystalline insulator

Cited by 35 publications

References 55 publications

Surface and bulk contributions to the second-harmonic generation in Bi2Se3

Surface and bulk contributions to the second-harmonic generation in Bi2Se3

Negative Longitudinal Magnetoresistance from the Anomalous N=0 Landau Level in Topological Materials

Giant Rashba Splitting in Pb_1–_xSn_xTe (111) Topological Crystalline Insulator Films Controlled by Bi Doping in the Bulk

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Inducing magnetism onto the surface of a topological crystalline insulator

Cited by 35 publications

References 55 publications

Surface and bulk contributions to the second-harmonic generation in Bi2Se3

Surface and bulk contributions to the second-harmonic generation in Bi2Se3

Negative Longitudinal Magnetoresistance from the Anomalous N=0 Landau Level in Topological Materials

Giant Rashba Splitting in Pb1–xSnxTe (111) Topological Crystalline Insulator Films Controlled by Bi Doping in the Bulk

Contact Info

Product

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About

Giant Rashba Splitting in Pb_1–_xSn_xTe (111) Topological Crystalline Insulator Films Controlled by Bi Doping in the Bulk