Title: Electric-field-tuned topological phase transition in ultrathin Na₃Bi

Abstract

The electric-field-induced quantum phase transition from topological to conventional insulator has been proposed as the basis of a topological field effect transistor. In this scheme, 'on' is the ballistic flow of charge and spin along dissipationless edges of a two-dimensional quantum spin Hall insulator, and 'off' is produced by applying an electric field that converts the exotic insulator to a conventional insulator with no conductive channels. Such a topological transistor is promising for low-energy logic circuits, which would necessitate electric-field-switched materials with conventional and topological bandgaps much greater than the thermal energy at room temperature, substantially greater than proposed so far. Topological Dirac semimetals are promising systems in which to look for topological field-effect switching, as they lie at the boundary between conventional and topological phases. Here we use scanning tunnelling microscopy and spectroscopy and angle-resolved photoelectron spectroscopy to show that mono- and bilayer films of the topological Dirac semimetal Na₃Bi are two-dimensional topological insulators with bulk bandgaps greater than 300 millielectronvolts owing to quantum confinement in the absence of electric field. On application of electric field by doping with potassium or by close approach of the scanning tunnelling microscope tip, the Stark effect completely closes the bandgap and re-opens itmore » as a conventional gap of 90 millielectronvolts. The large bandgaps in both the conventional and quantum spin Hall phases, much greater than the thermal energy at room temperature (25 millielectronvolts), suggest that ultrathin Na₃Bi is suitable for room-temperature topological transistor operation.« less

Authors:

Collins, James L. ^[1]; Tadich, Anton ^[2]; Wu, Weikang ^[3]; Gomes, Lidia C. ^[4]; Rodrigues, Joao N. B. ^[4]; Liu, Chang ^[1]; Hellerstedt, Jack ^[1]; Ryu, Hyejin ^[5]; Tang, Shujie ^[6]; Mo, Sung-Kwan ^[6]; Adam, Shaffique ^[7]; Yang, Shengyuan A. ^[8]; Fuhrer, Michael S. ^[1]; Edmonds, Mark T. ^[1]

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+ Show Author Affiliations

1. Monash Univ., Clayton, VIC (Australia)
2. Monash Univ., Clayton, VIC (Australia); Australian Synchrotron, Clayton, VIC (Australia)
3. Singapore Univ. of Technology and Design (Singapore)
4. National Univ. of Singapore (Singapore); Univ. of Illinois, Urbana-Champaign, IL (United States)
5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); Korea Inst. of Science and Technology, Seoul (Korea)
6. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
7. National Univ. of Singapore (Singapore); Yale-NUS College (Singapore)
8. Singapore Univ. of Technology and Design (Singapore); Nanjing Normal Univ., Nanjing (China)

Publication Date:

Mon Dec 10 00:00:00 EST 2018

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1542347

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Nature (London)

Additional Journal Information:

Journal Name: Nature (London); Journal Volume: 564; Journal Issue: 7736; Journal ID: ISSN 0028-0836

Publisher:

Nature Publishing Group

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS