Magnetic-field-induced insulator–metal transition in W-doped VO2 at 500 T

Abstract

Metal-insulator (MI) transitions in correlated electron systems have long been a central and controversial issue in material science. Vanadium dioxide (VO 2) exhibits a first-order MI transition at 340 K. For more than half a century, it has been debated whether electron correlation or the structural instability due to dimerised V ions is the more essential driving force behind this MI transition. Here, we show that an ultrahigh magnetic field of 500 T renders the insulator phase of tungsten (W)-doped VO 2 metallic. The spin Zeeman effect on the d electrons of the V ions dissociates the dimers in the insulating phase, resulting in the delocalisation of electrons. As the Mott-Hubbard gap essentially does not depend on the spin degree of freedom, the structural instability is likely to be the more essential driving force behind the MI transition.

Basic aspects of the metal–insulator transition in vanadium dioxide VO2: a critical review

“…As the spin gap ∆σ is quite large, it might be expected that a significant splitting could not be observed with available laboratory magnetic fields. However, the recent finding via optical means of a magnetic-field-induced insulator-metal transition in 6% W-doped VO 2 for an ultrahigh magnetic field of 500 T is a surprising result [140]. In this case it is not obvious that H should simply dissociate the M 1 V-V spin singlet by the Zeeman effect.…”

Decoupling the metal insulator transition and crystal field effects of VO2

“…Since Morin reported observing the metal-to-insulator transition (MIT) of VO 2 in 1959 1 , VO 2 has been widely studied to understand the origin of its MIT [2][3][4][5][6][7] and to use it in practical applications including smart windows, batteries, transistors, ultrafast switches, and gas sensors [8][9][10][11][12][13][14][15] . The MIT of VO 2 can be induced by different factors such as heat, an electric field, doping, oxygen vacancy, photons, and a magnetic field 1,[5][6][7][16][17][18][19][20] . A typical critical temperature (T c ) of the MIT of VO 2 is approximately 68 °C 5 .…”

“…A single crystal VO 2 has a distinct MIT temperature 22,31 while the MIT of grained VO 2 is dull, occurring over a wide range of temperature 7,21 . The T c and the MIT curve of VO 2 are very sensitive to structural disorder and strain 19,[32][33][34] . When a VO 2 film consists of grains, their structural disorder and distortion can take various forms, resulting in each grain having an individual T c .…”

A hybrid optoelectronic Mott insulator

“…2,[4][5][6][7][8][9][10] This transition is characterized by an abrupt change in the electrical resistivity by several orders of magnitude and can be controlled by modulating the temperature, doping, pressure, electric field, and to a small extent with laser light. [11][12][13][14][15][16][17][18][19][20][21][22][23][24] Some materials, such as VO 2 , also feature large changes in their optical properties across the MIT, making them attractive for optoelectronic applications. [25][26][27] Earlier studies 28,29 used VO 2 to modify the boundary conditions in heterostructures and this way to implement electrically controlled optical devices.…”