Magnetic-field induced multiple topological phases in pyrochlore iridates with Mott criticality

The interplay between electron correlation and spin–orbit coupling in solids has been proven to be an abundant gold mine for emergent topological phases. Here we report the results of systematic magnetotransport study on bandwidth-controlled pyrochlore iridates R2Ir2O7 near quantum metal-insulator transition (MIT). The application of a magnetic field along [001] crystallographic direction (H//[001]) significantly decreases resistivity while producing a unique Hall response, which indicates the emergence of the novel semi-metallic state in the course of the magnetic transformation from all-in all-out (AIAO, 4/0) to 2-in 2-out (2/2) spin configuration. For H//[111] that favours 3-in 1-out (3/1) configuration, by contrast, the resistivity exhibits saturation at a relatively high value typical of a semimetal. The observed properties can be identified to reflect the emergence of multiple Weyl semimetal states with varying numbers of Weyl points and line nodes in respective spin configurations. With tuning effective bandwidth, all these states appear to concentrate around the quantum MIT region, which may open a promising venue for topological phenomena and functions.

[1]  N. Tamura,et al.  Mobile metallic domain walls in an all-in-all-out magnetic insulator , 2015, Science.

[2]  Yong Baek Kim,et al.  Topological insulators and metal-insulator transition in the pyrochlore iridates , 2010, 1004.4630.

[3]  Leon Balents,et al.  Mott physics and band topology in materials with strong spin-orbit interaction , 2009, 0907.2962.

[4]  Yong Baek Kim,et al.  RKKY interactions and the anomalous Hall effect in metallic rare-earth pyrochlores. , 2013, Physical review letters.

[5]  K. Shimizu,et al.  Suppression of metal-insulator transition at high pressure and pressure-induced magnetic ordering in pyrochlore oxide Nd2Ir2O7 , 2011 .

[6]  M. Yokoyama,et al.  Emergence of Magnetic Long-range Order in Frustrated Pyrochlore Nd2Ir2O7with Metal–Insulator Transition , 2011, 1110.6605.

[7]  S. Bramwell,et al.  LETTER TO THE EDITOR: Frustration in Ising-type spin models on the pyrochlore lattice , 1998 .

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

[9]  S. Petit,et al.  Fluctuations and All-In-All-Out Ordering in Dipole-Octupole Nd(2)Zr(2)O(7). , 2015, Physical review letters.

[10]  Leon Balents,et al.  My title , 2013 .

[11]  Y. Maeno,et al.  Unconventional anomalous Hall effect enhanced by a noncoplanar spin texture in the frustrated Kondo lattice Pr2Ir2O7. , 2007, Physical review letters.

[12]  L. Balents,et al.  New Type of Quantum Criticality in the Pyrochlore Iridates , 2014, 1403.5255.

[13]  Ashvin Vishwanath,et al.  Subject Areas : Strongly Correlated Materials A Viewpoint on : Topological semimetal and Fermi-arc surface states in the electronic structure of pyrochlore iridates , 2011 .

[14]  Y. Hinatsu,et al.  Metal–Insulator Transitions in Pyrochlore Oxides Ln2Ir2O7 , 2011 .

[15]  H. Yamamoto,et al.  Quadratic Fermi node in a 3D strongly correlated semimetal , 2015, Nature Communications.

[16]  Takeshi Kondo,et al.  Slater to Mott Crossover in the Metal to Insulator Transition of Nd_{2}Ir_{2}O_{7}. , 2016, Physical review letters.

[17]  L. Balicas,et al.  Anisotropic hysteretic Hall effect and magnetic control of chiral domains in the chiral spin states of Pr2Ir2O7. , 2011, Physical Review Letters.

[18]  Y. Yamaji,et al.  Metallic Interface Emerging at Magnetic Domain Wall of Antiferromagnetic Insulator---Fate of Extinct Weyl Electrons , 2013, 1306.2022.

[19]  Yong Baek Kim,et al.  Topological and magnetic phases of interacting electrons in the pyrochlore iridates , 2011, 1105.6108.

[20]  Yoshinori Tokura,et al.  Critical features of colossal magnetoresistive manganites , 2006 .

[21]  X. Dai,et al.  Observation of the Chiral-Anomaly-Induced Negative Magnetoresistance in 3D Weyl Semimetal TaAs , 2015, 1503.01304.

[22]  T. M. Rice,et al.  Metal‐Insulator Transitions , 2003 .

[23]  Nazzal,et al.  Systematic study of insulator-metal transitions in perovskites RNiO3 (R=Pr,Nd,Sm,Eu) due to closing of charge-transfer gap. , 1992, Physical review. B, Condensed matter.

[24]  Y. Tokura,et al.  Pressure and magnetic field effects on metal-insulator transitions of bulk and domain wall states in pyrochlore iridates , 2015, 1507.04804.

[25]  T. Arima,et al.  Determination of long-range all-in-all-out ordering of Ir 4 + moments in a pyrochlore iridate Eu 2 Ir 2 O 7 by resonant x-ray diffraction , 2013 .

[26]  Y. Tokura,et al.  Anomalous domain-wall conductance in pyrochlore-type Nd$_{2}$Ir$_{2}$O$_{7}$ on the verge of metal-insulator transition , 2014 .

[27]  Y. Maeno,et al.  Crystal growth and structure of R2Ir2O7 (R = Pr, Eu) using molten KF , 2007 .

[28]  T. Sakakibara,et al.  Specific Heat of Kagomé Ice in the Pyrochlore Oxide Dy2Ti2O7 , 2002, cond-mat/0211326.

[29]  Y. Tokura,et al.  Magnetic Field-Induced Insulator-Semimetal Transition in a Pyrochlore Nd2Ir2O7. , 2015, Physical review letters.

[30]  Leon Balents,et al.  Field-induced quantum metal–insulator transition in the pyrochlore iridate Nd2Ir2O7 , 2015, Nature Physics.

[31]  Y. Tokura,et al.  Variation of charge dynamics in the course of metal-insulator transition for pyrochlore-type Nd2Ir2O7. , 2012, Physical review letters.

[32]  Y. Tokura,et al.  Variation of optical conductivity spectra in the course of bandwidth-controlled metal-insulator transitions in pyrochlore iridates , 2016 .

[33]  Bohm-Jung Yang,et al.  Quantum criticality of topological phase transitions in three-dimensional interacting electronic systems , 2014, Nature Physics.

[34]  L. Balicas,et al.  Metallic spin-liquid behavior of the geometrically frustrated Kondo lattice. , 2006, Physical review letters.

[35]  Gang Chen,et al.  Magnetic orders and topological phases from f - d exchange in pyrochlore iridates , 2012, 1208.4853.