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Journal Articles

Orbitally defined field-induced electronic state in a Kondo lattice

Lessux, G. G.*; Sakai, Hironori; Hattori, Taisuke*; Tokunaga, Yo; Kambe, Shinsaku; Kuhns, P. L.*; Reyes, A. P.*; Thompson, J. D.*; Pagliuso, P. G.*; Urbano, R. R.*

Physical Review B, 101(16), p.165111_1 - 165111_6, 2020/04

 Times Cited Count:7 Percentile:46.13(Materials Science, Multidisciplinary)

CeRhIn$$_5$$ is a Kondo-lattice prototype in which a magnetic field $$B^{ast}$$ $$simeq$$ 31T induces an abrupt Fermi-surface (FS) reconstruction and pronounced in-plane electrical transport anisotropy all within its antiferromagnetic state. Here we report low-temperature nuclear magnetic resonance (NMR) measurements revealing a pronounced decrease in the $$^{115}$$In formal Knight shift, without changes in crystal or magnetic structures, of CeRhIn$$_5$$ at fields ($$||c$$) spanning $$B^{ast}$$. We discuss the emergent state above $$B^{ast}$$ in terms of a change in Ce's 4$$f$$ orbitals that arises from field-induced evolution of crystal-electric field (CEF) energy levels. This change in orbital character enhances hybridization between the 4$$f$$ and the conduction electrons that leads ultimately to an itinerant quantum-critical point at $$B_{c0}$$ $$simeq$$ 50T.

Journal Articles

Emergent antiferromagnetism out of the "hidden-order" state in URu$$_2$$Si$$_2$$; High magnetic field nuclear magnetic resonance to 40 T

Sakai, Hironori; Urbano, R. R.*; Tokunaga, Yo; Kambe, Shinsaku; Suzuki, Michito; Kuhns, P. L.*; Reyes, A. P.*; Tobash, P. H.*; Ronning, F.*; Bauer, E. D.*; et al.

Physical Review Letters, 112(23), p.236401_1 - 236401_5, 2014/06

 Times Cited Count:7 Percentile:49.35(Physics, Multidisciplinary)

Very high field $$^{29}$$Si-NMR measurements using a fully $$^{29}$$Si-enriched URu$$_2$$Si$$_2$$ single crystal were carried out in order to microscopically investigate the "hidden order" (HO) state and adjacent magnetic phases in the high field limit. At the lowest measured temperature of 0.4 K, a clear anomaly reflecting a Fermi surface instability near 22 T inside the HO state is detected by the $$^{29}$$Si shift, $$^{29}K_c$$. Moreover, a strong enhancement of $$^{29}K_c$$ develops near a critical field $$H_{rm c}simeq 35.6$$ T, and the $$^{29}$$Si-NMR signal disappears suddenly at $$H_{rm c}$$, indicating the total suppression of the HO state. Nevertheless, a weak and shifted $$^{29}$$Si-NMR signal reappears for fields higher than $$H_{rm c}$$ at 4.2 K, providing evidence for a magnetic structure within the magnetic phase caused by the Ising-type anisotropy of the uranium ordered moments.

Journal Articles

Electronic inhomogeneity in a Kondo lattice

Bauer, E. D.*; Yang, Y.-F.*; Capan, C.*; Urbano, R. R.*; Miclea, C. F.*; Sakai, Hironori; Ronning, F.*; Graf, M. J.*; Balatsky, A. V.*; Movshovich, R.*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 108(17), p.6857 - 6861, 2011/04

 Times Cited Count:35 Percentile:81.51(Multidisciplinary Sciences)

Here, we report a manifestation of electronic inhomogeneity in a strongly correlated $$f$$-electron system, using CeCoIn$$_5$$ as an example. A thermodynamic analysis of its superconductivity, combined with nuclear quadrupole resonance measurements, shows that nonmagnetic impurities (Y, La, Yb, Th, Hg, and Sn) locally suppress unconventional superconductivity, generating an inhomogeneous electronic "Swiss cheese" due to disrupted periodicity of the Kondo lattice. Our analysis may be generalized to include related systems, suggesting that electronic inhomogeneity should be considered broadly in Kondo lattice materials.

Journal Articles

Charge-induced vortex lattice instability

Mounce, A. M.*; Oh, S.*; Mukhopadhyay, S.*; Halperin, W. P.*; Reyes, A. P.*; Kuhns, P. L.*; Fujita, Kazuhiro*; Ishikado, Motoyuki; Uchida, Shinichi*

Nature Physics, 7(2), p.125 - 128, 2011/02

 Times Cited Count:7 Percentile:47.47(Physics, Multidisciplinary)

It has been predicted that superconducting vortices should be electrically charged and that this effect is particularly enhanced for high-temperature superconductors. Hall effect and nuclear magnetic resonance (NMR) experiments suggest the existence of charge accumulation in the vortex core, but the effects are small and the interpretation controversial. Here we show that the Abrikosov vortex lattice, characteristic of the mixed state of superconductors, will become unstable at a sufficiently high magnetic field if there is charge trapped on the vortex core. Our NMR measurements of the magnetic fields generated by vortices in Bi$$_{2}$$Sr$$_{2}$$CaCu$$_{2}$$O$$_{8+y}$$ single crystals provide evidence for an electrostatically driven vortex lattice reconstruction with the magnitude of charge on each vortex pancake of $$sim2 times 10^{-3}e$$, depending on doping, in line with theoretical estimates.

Journal Articles

Spin-density wave near the vortex cores in the high-temperature superconductor Bi$$_{2}$$Sr$$_{2}$$CaCu$$_{2}$$O$$_{8+y}$$

Mounce, A. M.*; Oh, S.*; Mukhopadhyay, S.*; Halperin, W. P.*; Reyes, A. P.*; Kuhns, P. L.*; Fujita, Kazuhiro*; Ishikado, Motoyuki; Uchida, Shinichi*

Physical Review Letters, 106(5), p.057003_1 - 057003_4, 2011/02

 Times Cited Count:8 Percentile:50.98(Physics, Multidisciplinary)

Competition with magnetism is at the heart of high-temperature superconductivity, most intensely felt near a vortex core. To investigate vortex magnetism we have developed a spatially resolved probe based upon NMR spin-lattice-relaxation spectroscopy. With this approach we have found a spin-density wave associated with the vortex core in Bi$$_{2}$$Sr$$_{2}$$CaCu$$_{2}$$O$$_{8+y}$$, similar to checkerboard patterns in the local density of electronic states reported from scanning tunneling microscope experiments. We have determined both the spin-modulation amplitude and decay length from the vortex core in fields up to $$H$$ = 30 T.

Oral presentation

High-field $$^{29}$$Si-NMR study of URu$$_2$$Si$$_2$$

Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Urbano, R. R.*; Kuhns, P. L.*; Reyes, A. P.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*

no journal, , 

The heavy fermion superconductor URu$$_2$$Si$$_2$$ with $$T_{rm c}=1.7$$ K shows the "hidden order" at $$T_{rm O}=17.5$$ K. Below 1 K, it shows a first-order-transition at $$H_{rm c}sim 35$$ T from the hidden order phase to the magnetically ordered phase. The $$T$$-$$H$$ phase diagram for URu$$_2$$Si$$_2$$ above 35 T is known to be complicated but the details in the each phase above 35 T are unknown. We have been investigating the electronic state by means of $$^{29}$$Si-NMR in the higher field. The NMR experiment was done at National High Magnetic Field Laboratory (Tallahassee, FL, U.S.A.).

Oral presentation

High magnetic field NMR study of URu$$_2$$Si$$_2$$

Sakai, Hironori; Urbano, R. R.*; Tokunaga, Yo; Kambe, Shinsaku; Kuhns, P. L.*; Reyes, A. P.*; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*

no journal, , 

In order to microscopically investigate what happens around $$sim$$22 T and just above $$sim$$36 T in the lowest temperature, we have performed $$^{29}$$Si-NMR shift measurement using a $$^{29}$$Si-fully-enriched single crystal of URu$$_2$$Si$$_2$$. We have found a shift anomaly around 22 T and a critical increase toward $$sim$$36 T, corresponding to a slight change of total density of states (DOS) at $$sim$$22 T and increase of DOS toward $$sim$$36 T. Although the $$^{29}$$Si-NMR signal was lost by field sweeping just above $$sim$$36 T at the lowest temperature, the $$^{29}$$Si-NMR spectrum has been successfully obtained at 4.2 K in the magnetic phase just above $$sim$$36 T. From the spectral shape, we will discuss a possible magnetic structure in the magnetic phase.

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