Nonequilibrium Phase Precursors during a Photoexcited Insulator-to-Metal Transition in V_{2}O_{3}.

Here, we photoinduce and directly observe with x-ray scattering an ultrafast enhancement of the structural long-range order in the archetypal Mott system V_{2}O_{3}. Despite the ultrafast increase in crystal symmetry, the change of unit cell volume occurs an order of magnitude slower and coincides with the insulator-to-metal transition. The decoupling between the two structural responses in the time domain highlights the existence of a transient photoinduced precursor phase, which is distinct from the two structural phases present in equilibrium. X-ray nanoscopy reveals that acoustic phonons trapped in nanoscale twin domains govern the dynamics of the ultrafast transition into the precursor phase, while nucleation and growth of metallic domains dictate the duration of the slower transition into the metallic phase. The enhancement of the long-range order before completion of the electronic transition demonstrates the critical role the nonequilibrium structural phases play during electronic phase transitions in correlated electrons systems.

[1]  Masatoshi Imada,et al.  Metal-insulator transitions , 1998 .

[2]  Elbio Dagotto,et al.  Complexity in Strongly Correlated Electronic Systems , 2005, Science.

[3]  R. F. Haglund,et al.  Ultrafast insulator-metal phase transition in VO 2 studied by multiterahertz spectroscopy , 2011, 1104.2984.

[4]  M Marsi,et al.  Ultrafast evolution and transient phases of a prototype out-of-equilibrium Mott–Hubbard material , 2016, Nature Communications.

[5]  I. Robinson,et al.  Three-dimensional imaging of microstructure in Au nanocrystals. , 2003, Physical review letters.

[6]  Ivan K. Schuller,et al.  Ultrafast electron-lattice coupling dynamics in VO 2 and V 2 O 3 thin films , 2017, 1701.05531.

[7]  R Huber,et al.  Non-thermal separation of electronic and structural orders in a persisting charge density wave. , 2014, Nature materials.

[8]  Michelle A. Moram,et al.  X-ray diffraction of III-nitrides , 2009 .

[9]  H. Okamoto,et al.  Mott transition by an impulsive dielectric breakdown. , 2017, Nature materials.

[10]  Keith A. Nelson,et al.  Cooperative photoinduced metastable phase control in strained manganite films. , 2016, Nature materials.

[11]  D. N. Basov,et al.  Electrodynamics of the vanadium oxides VO2 and V2O3 , 2008, 0803.2739.

[12]  J. P. Remeika,et al.  Metal-Insulator Transitions in Pure and Doped V 2 O 3 , 1973 .

[13]  Ivan K. Schuller,et al.  Nanotextured phase coexistence in the correlated insulator V2O3 , 2016, Nature Physics.

[14]  M Sikorski,et al.  A time-dependent order parameter for ultrafast photoinduced phase transitions. , 2014, Nature materials.

[15]  Ahmed H. Zewail,et al.  4D Visualization of Transitional Structures in Phase Transformations by Electron Diffraction , 2007, Science.

[16]  M. Altarelli,et al.  Orbital Occupancy Order in V2O3: Resonant X-Ray Scattering Results. , 1999 .

[17]  Michele Fabrizio,et al.  Low-temperature magnetic ordering and structural distortions in vanadium sesquioxideV2O3 , 2015, 1502.04555.

[18]  Ivan K Schuller,et al.  Multiple avalanches across the metal-insulator transition of vanadium oxide nanoscaled junctions. , 2008, Physical review letters.

[19]  M. Azuma,et al.  Visualization of the emergence of the pseudogap state and the evolution to superconductivity in a lightly hole-doped Mott insulator , 2012, Nature Physics.

[20]  G. K. Williamson,et al.  X-ray line broadening from filed aluminium and wolfram , 1953 .

[21]  Tsuyoshi Murata,et al.  {m , 1934, ACML.

[22]  Ivan K. Schuller,et al.  Dynamic conductivity scaling in photoexcited V 2 O 3 thin films , 2014, 1410.6804.

[23]  D. Ratner,et al.  First lasing and operation of an ångstrom-wavelength free-electron laser , 2010 .

[24]  J. P. Remeika,et al.  Metal-Insulator Transition in(V1−xCrx)2O3 , 1970 .

[25]  Faraday Discuss , 1985 .

[26]  I. Zeljkovic,et al.  Imaging the Impact of Single Oxygen Atoms on Superconducting Bi2+ySr2–yCaCu2O8+x , 2012, Science.

[27]  Marcin Sikorski,et al.  Performance of a beam-multiplexing diamond crystal monochromator at the Linac Coherent Light Source. , 2014, The Review of scientific instruments.

[28]  I. Valmianski,et al.  Coercivity enhancement in V2O3/Ni bilayers driven by nanoscale phase coexistence , 2014 .

[29]  A. Georges,et al.  Universality and Critical Behavior at the Mott Transition , 2003, Science.

[30]  M. Fabrizio,et al.  Field-Driven Mott Gap Collapse and Resistive Switch in Correlated Insulators. , 2016, Physical review letters.

[31]  Jörg Maser,et al.  A hard X-ray nanoprobe beamline for nanoscale microscopy , 2012, Journal of synchrotron radiation.

[32]  G. Aeppli,et al.  Scale-free structural organization of oxygen interstitials in La2CuO4+y , 2010, Nature.

[33]  M. Marezio,et al.  Crystal Structure of the Low-Temperature Antiferromagnetic Phase of V 2 O 3 , 1970 .

[34]  K. Rossnagel,et al.  How fast can a Peierls-Mott insulator be melted? , 2014, Faraday discussions.

[35]  O. M. Magnussen,et al.  Photoinduced Enhancement of the Charge Density Wave Amplitude. , 2015, Physical review letters.

[36]  Juan Trastoy,et al.  Effect of disorder on the metal-insulator transition of vanadium oxides: Local versus global effects , 2015 .

[37]  Mohamed Chaker,et al.  A photoinduced metal-like phase of monoclinic VO2 revealed by ultrafast electron diffraction , 2014, Science.

[38]  문정진 § 19 , 2000 .

[39]  H. Park,et al.  Mechanism of coherent acoustic phonon generation under nonequilibrium conditions , 2005 .