Electronic Phases in Low-Dimensional Electron Systems under Ultra-High Magnetic Fields

本工作的目的是寻找和澄清在100 T以上的超高磁场下低维电子系统中出现的新的电子相。在目前的工作中，我们已经尝试了测量电导脉冲超高磁场的宽度为几微秒，这已经产生的电磁通量压缩方法或单匝线圈直接放电方法。为了克服巨大的感应电压，巨大的放电噪声，和样品加热由于涡流的实验困难，我们已经开发了射频输运测量和样品的微细加工技术。超高磁场下的电子关联石墨和铋的高场磁输运测量表明，在高场量子极限附近的Shubnikov-de哈斯振荡的位置偏离了低场振荡的预期位置。这一事实有力地表明，自我能量校正 ...更多信息 在高场量子极限下，电子轨道变得小于电子距离，电子相关引起的电子相互作用增强.超高磁场下的布洛赫电子系统在具有双Peierls跃迁的准一维导体NbSe_3中，低温相保留一个小而薄的电子袋。我们发现，在高场量子极限下，磁电阻单调减小，在高场量子极限下，所有的电子都处于最低的朗道能级。这种反常行为反映了由于CDW间隙的磁击穿导致的最低朗道能级的哈珀展宽。超高磁场下的二维电子系统为了研究量子霍尔系统中的高场相位，我们发展了阻抗在零电阻和高电阻之间振荡的量子霍尔系统的射频输运测量技术。我们制作了特殊形状的Corbino样品，并成功地测量了高达100 T的σ_（<xx>Ck）。在80 T左右观察到了1/3分数霍尔态的结构。少

The purpose of this work is to find and to clarify new electronic phases which appear in low-dimensional electron systems under ultra-high magnetic fields beyond 100T. In the present work, we have tried to measure electric conduction under pulsed ultra-high magnetic fields with the width of several us, which have been generated by the electromagnetic flux compression method or the single-turn-coil direct discharge method. In order to overcome the experimental difficulties of huge induced voltage, huge discharge noise, and sample heating due to eddy current, we have developed techniques for RF transport measurement and microfabrication of samples.1. Electron Correlation under Ultra-High Magnetic FieldsHigh-field magnetotransport measurements for graphite and bismuth have revealed that the posions of the Shubnikov-de Haas oscillations near the high-magnetic-field quantum limit deviate from those expected from low-field oscillations. This fact strongly suggests that the self energy correc … More tion due to electron correlation is enhanced at high-field quantum limit where the electron orbit becomes smaller than the electron distance.2. Bloch Electron Systems under Ultra-High Magnetic FieldsIn quasi-one-dimensional conductor NbSe_3 which shows double Peierls transitions, one small thin electron pocket remains at the low-temperature phase. We have found that the magnetoresistance monotonously decreases in the high-field quantum limit where all electrons lie in the lowest Landau level. This anomalous behavior reflects the Harper broadening of the lowest Landau level due to the magnetic breakdown across the CDW gap.3. Two-Dimensional Electron System under Ultra-High Magnetic FieldsIn order to investigate the high-field phases in quantum Hall systems, we have developed the techniques for RF transport measurement in quantum Hall systems whose impedance oscillates between zero and high resistance. We have fabricated the Corbino samples with special shape, and have succeeded to measure σ_<xx>Ck up to 100T. A structure corresponding to the 1/3 fractional Hall state was observed about at 80T. Less