Title: Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor

Journal Article · · Nano Letters
ORCiD logo [1];  [1];  [2];  [1];  [1];  [1];  [1];  [1];  [3];  [4];  [4];  [5];  [6];  [5];  [1]
  1. Boston College, Chestnut Hill, MA (United States). Dept. of Physics
  2. Harvard Univ., Cambridge, MA (United States). Dept. of Physics
  3. Department of Physics and Astronomy, Seoul National University (SNU), Seoul 08826, Republic of Korea
  4. National Inst. for Materials Science, Tsukuba (Japan)
  5. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  6. Seoul National Univ. (Korea, Republic of). Dept.of Physics and Astronomy
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Combining topology and superconductivity provides a powerful tool for investigating fundamental physics as well as a route to fault-tolerant quantum computing. There is mounting evidence that the Fe-based superconductor FeTe0.55Se0.45 (FTS) may also be topologically nontrivial. Should the superconducting order be s±, then FTS could be a higher order topological superconductor with helical hinge zero modes (HHZMs). To test the presence of these modes, we have fabricated normal-metal/superconductor junctions on different surfaces via 2D atomic crystal heterostructures. As expected, junctions in contact with the hinge reveal a sharp zero bias anomaly that is absent when tunneling purely into the c-axis. Additionally, the shape and suppression with temperature are consistent with highly coherent modes along the hinge and are incongruous with other origins of zero bias anomalies. Additional measurements with soft-point contacts in bulk samples with various Fe interstitial contents demonstrate the intrinsic nature of the observed mode. Thus, we provide evidence that FTS is indeed a higher order topological superconductor.

Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Grant/Contract Number:
SC0012704
OSTI ID:
1566819
Report Number(s):
BNL-212104-2019-JAAM
Journal Information:
Nano Letters, Journal Name: Nano Letters Journal Issue: 8 Vol. 19; ISSN 1530-6984
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

References (53)

Zero-energy vortex bound state in the superconducting topological surface state of Fe(Se,Te) text January 2018
Doppler shift of zero energy Andreev bound state journal May 2003
McMillan–Rowell oscillations observed in c-axis Au/Bi2Sr2CaCu2O8+δ junctions journal August 2004
Conductance Spectroscopy of Exfoliated Thin Flakes of Nb x Bi 2 Se 3 journal November 2018
Kondo effect in an integer-spin quantum dot journal June 2000
Spin liquids in frustrated magnets journal March 2010
Exponential protection of zero modes in Majorana islands journal March 2016
Epitaxy of advanced nanowire quantum devices journal August 2017
Anisotropic structure of the order parameter in FeSe0.45Te0.55 revealed by angle-resolved specific heat journal November 2010
Proximity-induced high-temperature superconductivity in the topological insulators Bi2Se3 and Bi2Te3 journal January 2012
From (π,0) magnetic order to superconductivity with (π,π) magnetic resonance in Fe1.02Te1−xSex journal July 2010
Acoustic higher-order topological insulator on a kagome lattice journal December 2018
Observation of higher-order topological acoustic states protected by generalized chiral symmetry journal December 2018
Higher-order topology in bismuth journal July 2018
Multiple topological states in iron-based superconductors journal September 2018
Quantum Hall effect based on Weyl orbits in Cd3As2 journal December 2018
Andreev bound states in high- T c superconducting junctions journal April 2001
Point-contact Andreev-reflection spectroscopy in Fe(Te,Se) films: multiband superconductivity and electron-boson coupling journal November 2014
Surface superconductivity in the Weyl semimetal MoTe 2 detected by point contact spectroscopy journal August 2018
Transition from metallic to tunneling regimes in superconducting microconstrictions: Excess current, charge imbalance, and supercurrent conversion journal April 1982
Effect of magnetic field on impurity bound states in high- T c superconductors journal June 2001
Edge states and determination of pairing symmetry in superconducting Sr 2 RuO 4 journal February 2002
Observation of McMillan-Rowell like oscillations in underdoped YBa 2 Cu 3 O y junctions oriented along the node of the d -wave order parameter journal April 2004
London penetration depth and superfluid density of single-crystalline Fe 1 + y ( Te 1 − x Se x ) and Fe 1 + y ( Te 1 − x S x ) journal May 2010
Anisotropic superconducting properties of single-crystalline FeSe 0.5 Te 0.5 journal June 2010
Macroscopic physical properties and spin dynamics in the layered superconductor Fe 1 + δ Te 1 − x Se x journal August 2010
Anisotropic fluctuations and quasiparticle excitations in FeSe 0.5 Te 0.5 journal September 2010
Isotropic superconducting gaps with enhanced pairing on electron Fermi surfaces in FeTe 0.55 Se 0.45 journal March 2012
FeTe 0.55 Se 0.45 : A multiband superconductor in the clean and dirty limit journal April 2015
Topological nature of the FeSe 0.5 Te 0.5 superconductor journal September 2015
Orbital selective pairing and gap structures of iron-based superconductors journal May 2017
Quantum perfect crossed Andreev reflection in top-gated quantum anomalous Hall insulator–superconductor junctions journal June 2017
Electron temperature and tunnel coupling dependence of zero-bias and almost-zero-bias conductance peaks in Majorana nanowires journal November 2017
Evidence for a cos  ( 4 φ ) Modulation of the Superconducting Energy Gap of Optimally Doped FeTe 0.6 Se 0.4 Single Crystals Using Laser Angle-Resolved Photoemission Spectroscopy journal December 2012
Reflection-Symmetric Second-Order Topological Insulators and Superconductors journal December 2017
( d − 2 ) -Dimensional Edge States of Rotation Symmetry Protected Topological States journal December 2017
Majorana Corner Modes in a High-Temperature Platform journal August 2018
High-Temperature Majorana Corner States journal October 2018
Helical Hinge Majorana Modes in Iron-Based Superconductors journal May 2019
Excess conductance of superconductor-semiconductor interfaces due to phase conjugation between electrons and holes journal July 1992
Zero Bias Conductance Peak Enhancement in Bi 2 Sr 2 CaCu 2 O 8 / Pb Tunneling Junctions journal February 1998
Doppler Shift of the Andreev Bound States at the YBCO Surface journal November 1999
Robust and Clean Majorana Zero Mode in the Vortex Core of High-Temperature Superconductor ( Li 0.84 Fe 0.16 ) OHFeSe journal December 2018
Andreev–Saint-James reflections: A probe of cuprate superconductors journal March 2005
Non-Abelian anyons and topological quantum computation journal September 2008
Weyl and Dirac semimetals in three-dimensional solids journal January 2018
Experimental Realization of a Three-Dimensional Topological Insulator, Bi2Te3 journal June 2009
Unconventional s-Wave Superconductivity in Fe(Se,Te) journal April 2010
Quantized electric multipole insulators journal July 2017
Observation of topological superconductivity on the surface of an iron-based superconductor journal March 2018
Evidence for Majorana bound states in an iron-based superconductor journal August 2018
Symmetry and Topology in Superconductors –Odd-Frequency Pairing and Edge States– journal January 2012
Pairing Mechanism in Fe-Based Superconductors journal March 2012

Cited By (4)

Superconductivity of Topological Surface States and Strong Proximity Effect in Sn 1− x Pb x Te–Pb Heterostructures journal November 2019
Superconductivity of Topological Surface States and Strong Proximity Effect in Sn 1–x Pb x Te‐Pb Heterostructures journal September 2020
FeTe 0.55 Se 0.45 van der Waals tunneling devices journal August 2019
Higher-Order Topological Odd-Parity Superconductors journal October 2019

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