Probing a topological quantum critical point in semiconductor-superconductor heterostructures

Tewari, Sumanta; Sau, Jay D.; Scarola, V. W.; Zhang, Chuanwei; Sarma, S. Das

doi:10.1103/physrevb.85.155302

Cited by 29 publications

(29 citation statements)

References 33 publications

(101 reference statements)

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“…[1][2][3][4] Testing such predictions requires advanced experiments, for example, measurements that can reveal unconventional quantum phase transitions. 5 Here, we report an unusual insulator to metal quantum phase transition in the pressure-temperature phase diagram of the pyrochlore iridate Eu 2 Ir 2 O 7 .…”

Section: Introductionmentioning

confidence: 82%

Pressure-tuned insulator to metal transition inEu2Ir2O7

et al. 2012

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We have studied the effect of pressure on the pyrochlore iridate Eu 2 Ir 2 O 7 , which, at ambient pressure, has a thermally driven insulator to metal transition at T MI ∼ 120 K. As a function of pressure, the insulating gap closes, apparently continuously near P ∼ 6 GPa. However, rather than T MI going to zero as expected, the insulating ground state crosses over to a metallic state with a negative temperature coefficient of resistivity, suggesting that these ground states have a novel character. The high-temperature state also crosses over near 6 GPa from an incoherent to a conventional metal, implying that there is a connection between the high-and the low-temperature states.

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Section: Introductionmentioning

confidence: 82%

Pressure-tuned insulator to metal transition inEu2Ir2O7

et al. 2012

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“…Beside the ARPES and band structure calculations, there has been a growing number of experiments 97–124 and theoretical studies 125–187 devoted to helical transport in 3DTI materials. Like in the QSHIs, the surface charge carriers in 3DTIs are characterized by a well‐defined spin helicity, i.e., the locking of the spin and momentum directions.…”

Section: Introductionmentioning

confidence: 99%

Spin‐helical transport in normal and superconducting topological insulators

Tkachov

Hankiewicz

2013

Physica Status Solidi (b)

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31 85141In a topological insulator (TI) the character of electron transport varies from insulating in the interior of the material to metallic near its surface. Unlike, however, ordinary metals, conducting surface states in TIs are topologically protected and characterized by spin helicity whereby the direction of the electron spin is locked to the momentum direction. In this paper we review selected topics regarding recent theoretical and experimental work on electron transport and related phenomena in two-dimensional (2D) and three-dimensional (3D) TIs.The review provides a focused introductory discussion of the quantum spin Hall effect in HgTe quantum wells as well as transport properties of 3DTIs such as surface weak antilocalization, the half-integer quantum Hall effect, s þ p-wave induced superconductivity, superconducting Klein tunneling, topological Andreev bound states and related Majorana midgap states. These properties of TIs are of practical interest, guiding the search for the routes towards topological spin electronics. 1 Introduction The situation when a material behaves as a metal in terms of its electric conductivity and, at the same time, as an insulator in terms of its band structure is extremely unconventional from the viewpoint of the standard classification of solids. That is why the recent discovery of a class of such materials -topological insulators (TIs) -has generated much interest (see e.g., reviews [1,2]). The dual properties of the TIs are especially well pronounced in two-dimensional (2D) systems which are also known as quantum spin-Hall insulators (QSHIs) [3][4][5][6][7]. In QSHIs, the metallic electric conduction is associated with propagating states that occur only near the sample edges, while the conduction in the interior is suppressed by a band gap like in ordinary band insulators. These edge states originate from intrinsic spin-orbit (SO) coupling and are profoundly different from those appearing in quantum Hall systems in a strong perpendicular magnetic field [8,9]. The key distinction lies in the role of the time reversal symmetry. In the QSHIs the SO coupling preserves the time-reversal symmetry, resulting in a pair of counter-propagating channels on the same edge as opposed to one-way directed (chiral) edge states in quantum Hall systems. Remarkably, the spin and momentum directions of the two QSHI edge channels are locked in the opposite ways so that these states are characterized by opposite spin helicities and orthogonal

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“…[9][10][11] Since neither special materials nor exotic physics are needed to produce the non-Abelian excitations, this structure is potentially one of the simplest to probe non-Abelian quantum matter and therefore has attracted considerable attention in the recent literature. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] The non-Abelian excitations in the semiconductor in this proposal, are the zero-energy Majorana fermions, defined by the self-hermitian operators γ 0 ; γ † 0 = γ 0 , localized at vortices or the sample edges induced by the superconducting proximity effect. 9 Even though the non-Abelian excitations in the ν = 5/2 FQH system are charged, the Majorana excitations in the semiconductor are charge-neutral.…”

Section: Introductionmentioning

confidence: 99%

Probing non-Abelian statistics with Majorana fermion interferometry in spin-orbit-coupled semiconductors

Tewari

Sarma

2011

Phys. Rev. B

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The list of quantum mechanical systems with non-Abelian statistics has recently been expanded by including generic spin-orbit-coupled semiconductors (e.g., InAs) in proximity to a s-wave superconductor. Demonstration of the anyonic statistics using Majorana fermion interferometry in this system is a necessary first step towards topological quantum computation (TQC). However, since all isolated chiral edges that can be created in the semiconductor are charge neutral, it is not clear if electrically controlled interferometry is possible in this system. Here we show that when two isolated chiral Majorana edges are brought into close contact, the resultant interface supports charge current, enabling electrically controlled Majorana fermion interferometry in the semiconductor structure. Such interferometry experiments on the semiconductor are analogous to similar interferometry experiments on the ν = 5/2 fractional quantum Hall systems and on the surface of a 3D strong topological insulator, illustrating the usefulness of the 2D semiconductor heterostructure as a suitable TQC platform. In particular, we proposed Majorana interferometers may be the most direct method for establishing non-Abelian braiding statistics in topological superconductors.

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Probing a topological quantum critical point in semiconductor-superconductor heterostructures

Cited by 29 publications

References 33 publications

Pressure-tuned insulator to metal transition inEu2Ir2O7

Pressure-tuned insulator to metal transition inEu2Ir2O7

Spin‐helical transport in normal and superconducting topological insulators

Probing non-Abelian statistics with Majorana fermion interferometry in spin-orbit-coupled semiconductors

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