title: Measurement of a solid-state triple point at the metal-insulator transition in VO2.
abstract: First-order phase transitions in solids are notoriously challenging to study. The combination of change in unit cell shape, long range of elastic distortion and flow of latent heat leads to large energy barriers resulting in domain structure, hysteresis and cracking. The situation is worse near a triple point, where more than two phases are involved. The well-known metal-insulator transition in vanadium dioxide, a popular candidate for ultrafast optical and electrical switching applications, is a case in point. Even though VO2 is one of the simplest strongly correlated materials, experimental difficulties posed by the first-order nature of the metal-insulator transition as well as the involvement of at least two competing insulating phases have led to persistent controversy about its nature. Here we show that studying single-crystal VO2 nanobeams in a purpose-built nanomechanical strain apparatus allows investigation of this prototypical phase transition with unprecedented control and precision. Our results include the striking finding that the triple point of the metallic phase and two insulating phases is at the transition temperature, Ttr = Tc, which we determine to be 65.0 ± 0.1 °C. The findings have profound implications for the mechanism of the metal-insulator transition in VO2, but they also demonstrate the importance of this approach for mastering phase transitions in many other strongly correlated materials, such as manganites and iron-based superconductors.
authors: Department of Physics, University of Washington, Seattle, Washington 98195, USA.
authors: Jae Hyung
authors: JH
authors: Park
authors: Jim M
authors: JM
authors: Coy
authors: T Serkan
authors: TS
authors: Kasirga
authors: Chunming
authors: C
authors: Huang
authors: Zaiyao
authors: Z
authors: Fei
authors: Scott
authors: S
authors: Hunter
authors: David H
authors: DH
authors: Cobden
references: Nano Lett. 2011 Aug 10;11(8):3207-13
references: 21736336
references: Nature. 2012 Jul 25;487(7408):459-62
references: 22837001
references: Science. 2007 Dec 14;318(5857):1750-3
references: 18079396
references: Nano Lett. 2010 Jun 9;10(6):2003-11
references: 20455527
references: Phys Rev Lett. 2011 Jul 1;107(1):016401
references: 21797557
references: Nano Lett. 2010 Jul 14;10(7):2667-73
references: 20586406
references: Nat Nanotechnol. 2012 Nov;7(11):723-7
references: 23085645
references: Nano Lett. 2010 Nov 10;10(11):4409-16
references: 20939599
references: Phys Rev Lett. 2007 Nov 30;99(22):226401
references: 18233305
references: Phys Rev Lett. 2005 Jan 21;94(2):026404
references: 15698203
references: Nano Lett. 2006 Oct;6(10):2313-7
references: 17034103
references: Nano Lett. 2009 Dec;9(12):4527-32
references: 19902918
references: Nano Lett. 2010 May 12;10(5):1574-81
references: 20377237
references: Phys Rev Lett. 2007 Sep 14;99(11):116401
references: 17930454
references: Phys Rev Lett. 1994 Nov 28;73(22):3042
references: 10057270
references: Science. 2012 Aug 10;337(6095):710-2
references: 22879513
references: Nat Nanotechnol. 2009 Nov;4(11):732-7
references: 19893528
references: Science. 2013 Mar 22;339(6126):1402-5
references: 23520104
references: Nat Nanotechnol. 2009 Jul;4(7):420-4
references: 19581893
references: Nano Lett. 2009 Oct;9(10):3392-7
references: 19785429