Study of Strongly Correlated Condensed-Matter Systems under Multiple Extreme Conditions

This研究项目was planed to investigate the novel electron phases in stronglycorrelated-electron systems, heavy-fermionhigh-temperature cuprate and low dimensional organic materials under multiple extreme conditions.1. On the basis of Cu-NQR measurements，we have found that the ground state in a series of Ce - D2x - D2Cu - D22 - D2Si - D22 - D2 compoundsevolves from magnetically ordered phase at x=0.975 to heavy-electron superconducting (SC) phase atx=1.025. The sample of x=0.99 does not exhibit any trace of magnetic phase transition down to 0.012k,but is dominated by slow magnetic fluctuations with low frequencies comparable to the NQR frequency。For the samples of x=1.00 and 1.025 such a state is expelled by the onset of the SC state.2. Fromthe NQR results under pressure (P) on near stoichiometric Ce - d20.99 - D2Cu - D22 - D2Si - D22 - D2（T - i D2c D2=0.65 K），an exotic superconducting state due to an interplay with slowly-varying-magnetic-…fluctuation-modes was found to be suppressed and replaced by a strong heavy-fermion SCphase at minute pressures exceeding P ~ 0.2 GPa. The T - D21 - D2 data in The high-P range 0.85-2.58 GPaare shown to be accountable by the SCR theory . In P<0.2 GPa，an exotic interplay between magnetic and SC phase is implied.3. The magnetic-field dependencies of magnetic-field dependencies ofthe pseudogap behavior in the underdoped YBa - D22 - D2Cu - D24 - D2O - D28 - D2 (Y1248) was measured up23 T at the NHMF Laboratory （Tallahassee）Florida) and up to 28.5 T on the slightly overdoped TISr i D22 i D2CaCu i D22 i D2O i d26.88 i D2 withD2c D2= 68k (TI1212). In the overdoped TI1212，we showed that the scalings found in the T and magnetic field dependencies of 1Knight shift are consistent with the superconducting (SC) fluctuations. By contrast，even though 23.2 T reduces T y D2c D2 by 26% in Y1248，no effect is seen on the normal-state pseudogap behavior. This was ascribed as due to the strongercoupling nature of the pairing than in ti12 . we have thus clarified the novel characteristics ofanomalous magentism and unconventional superconductivity in the heavy-fermion and high-T - 2cuprate oxides under multiple extreme conditions. The present research project enabled us to opennew frontiers in the field. Less

This research project was planed to investigate the novel electron phases in strongly correlated-electron systems, heavy-fermion, high-temperature cuprate and low dimensional organic materials under multiple extreme conditions. Obtained results are listed below.1. On the basis of Cu-NQR measurements, we have found that the ground state in a series of CeィイD2xィエD2CuィイD22ィエD2SiィイD22ィエD2 compounds evolves from magnetically ordered phase at x=0.975 to heavy-electron superconducting (SC) phase at x=1.025. The sample of x=0.99 does not exhibit any trace of magnetic phase transition down to 0.012 K, but is dominated by slow magnetic fluctuations with low frequencies comparable to the NQR frequency. For the samples of x=1.00 and 1.025 such a state is expelled by the onset of the SC state.2. From the NQR results under pressure (P) on near stoichiometric CeィイD20.99ィエD2CuィイD22ィエD2SiィイD22ィエD2 (TィイD2cィエD2=0.65 K), an exotic superconducting (SC) state due to an interplay with slowly-varying-magnetic- … More fluctuation-modes was found to be suppressed and replaced by a strong heavy-fermion SC phase at minute pressures exceeding P〜0.2 GPa. The TィイD21ィエD2 data in the high-P range 0.85-2.58 GPa are shown to be accountable by the "SCR theory". In P<0.2 GPa, an exotic interplay between magnetic and SC phase is implied.3. The magnetic-field dependencies of the pseudogap behavior in the underdoped YBaィイD22ィエD2CuィイD24ィエD2OィイD28ィエD2 (Y1248) was measured up to 23 T at the NHMF Laboratory (Tallahassee, Florida) and up to 28.5 T on the slightly overdoped TISrィイD22ィエD2CaCuィイD22ィエD2OィイD26.88ィエD2 with TィイD2cィエD2=68 K (TI1212). In the overdoped TI1212, we showed that the scalings found in the T and magnetic field dependencies of 1/TィイD21ィエD2 and Knight shift are consistent with the superconducting (SC) fluctuations. By contrast, even though 23.2 T reduces TィイD2cィエD2 by 26% in Y1248, no effect is seen on the normal-state pseudogap behavior. This was ascribed as due to the stronger coupling nature of the pairing than in TI1212.We have thus clarified the novel characteristics of anomalous magentism and unconventional superconductivity in the heavy-fermion and high-TィイD2cィエD2 cuprate oxides under multiple extreme conditions. The present research project enabled us to open new frontiers in the field. Less